Isolated Anophthalmia-Microphthalmia Syndrome

Mendelian MONDO:0016764 Pathograph 52 Show in embeddings browser hereditary disease developmental eye disorder

Isolated anophthalmia-microphthalmia syndrome is the non-syndromic pole of the microphthalmia-anophthalmia-coloboma (MAC) spectrum: a severe congenital developmental eye malformation in which the globe is absent (anophthalmia) or abnormally small (microphthalmia). Mechanistically it is best understood as failure at one of three sequential steps of early ocular morphogenesis — lateral evagination of the eye field into paired optic vesicles (4th week), invagination of the distal optic vesicle to form the bilayered optic cup, and fusion of the nasal and temporal edges of the optic fissure (7th week). Which step fails largely determines the resulting phenotype: the earliest and most complete failures abort globe formation and produce anophthalmia, partial failures of invagination and growth produce microphthalmia, and failure of the last step produces coloboma. The disorder is highly genetically heterogeneous; SOX2 (10-15% of all A/M) and OTX2 are the commonest single-gene causes, with the eye-field and lens transcription factors RAX, VSX2, PAX6, FOXE3 and MAB21L2, the BMP-family ligands GDF3 and GDF6, the posterior-microphthalmia genes MFRP and PRSS56, and the retinoic-acid-pathway genes ALDH1A3, STRA6, RBP4 and RARB also implicated, alongside copy-number and regulatory variants. Non-genetic first-trimester insults — gestational infection, maternal vitamin A deficiency, and teratogens such as thalidomide and retinoids — contribute a minority of cases.

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Inheritance

Autosomal dominant inheritance HP:0000006

The dominant arm is driven by haploinsufficiency of dosage-sensitive developmental transcription factors, chiefly SOX2 and OTX2. The great majority of SOX2 variants arise de novo, but germline mosaicism is documented and must be factored into recurrence-risk counselling. OTX2 disease shows marked non-penetrance and variable expressivity even within a single family.

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"SOX2-related anophthalmia syndrome is transmitted in an autosomal dominant"

States the dominant transmission of the commonest A/M gene.

Autosomal recessive inheritance HP:0000007

Biallelic variants in RAX, VSX2, ALDH1A3, FOXE3, MFRP and PRSS56 cause recessive disease, typically bilateral and severe, and are enriched in consanguineous pedigrees although compound heterozygosity occurs in non-consanguineous families. Heterozygous carriers are usually unaffected.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:21976963 SUPPORT Human Clinical

"Mutations in VSX2 represent an important cause of autosomal recessive microphthalmia in consanguineous pedigrees."

Documents the autosomal recessive arm of isolated microphthalmia.

X-linked inheritance HP:0001417

An X-linked numbered locus exists in the isolated series (MCOPCB1, MONDO:0024549 / OMIM:300345), and X-linked genes such as BCOR contribute to the wider MAC spectrum. Deletions involving the X chromosome were among the causal findings in a prospective MAC cohort.

X-linked inheritance

Show evidence (1 reference)

PMID:36192130 SUPPORT Human Clinical

"novel variants in six known MAC genes (SOX2, KMT2D, MAB21L2, ALDH1A3, BCOR and"

Identifies the X-linked gene BCOR among causal findings in a real-world MAC cohort; the numbered X-linked locus MCOPCB1 itself is documented in MONDO/OMIM rather than in this paper, so this is scored PARTIAL.

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Subtypes

Anophthalmia (clinical and true)

Complete absence of the globe in the presence of ocular adnexa (eyelids, conjunctiva, lacrimal apparatus). "Clinical anophthalmia" denotes absence of any visible ocular structure although a histologically detectable remnant may persist; "true" anophthalmia denotes total absence of any ocular tissue. The boundary with extreme microphthalmia is a fine one. Represents failure at the earliest step (optic vesicle evagination/induction) and is the phenotype most strongly enriched for a molecular diagnosis.

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"Anophthalmia refers to complete absence of the globe in the presence of ocular adnexa"

GeneReviews definition of anophthalmia within the MAC spectrum.

Simple (non-colobomatous) microphthalmia

A globe of reduced size (total axial length at least 2 SD below the age-adjusted mean; <21 mm in adults, <14 mm in newborns) that is otherwise anatomically intact. Reflects a quantitative failure of optic-cup growth rather than a discrete structural closure defect.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Simple microphthalmia refers to an anatomically intact eye with a reduced axial length, without"

Establishes the simple-versus-complex microphthalmia classification used for this subtype.

Complex microphthalmia (with segment anomalies)

Microphthalmia accompanied by anterior-segment abnormalities (Axenfeld-Rieger anomaly, Peters anomaly, sclerocornea, cataract) or posterior-segment abnormalities (persistent primitive vitreous, chorioretinal coloboma, retinal dysplasia). Implies additional failure of anterior-segment or retinal differentiation on top of reduced globe growth.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"sclerocornea and cataract) or of the posterior segment (persistence of primitive vitreous, chorioretinal"

Enumerates the segment anomalies that define complex microphthalmia.

Colobomatous microphthalmia MONDO:0000170

Microphthalmia combined with an optic fissure closure defect. This is the third-step (fissure-closure) arm of the spectrum and corresponds to MONDO child term MONDO:0000170; it is curated in detail in the separate `Microphthalmia_with_Coloboma` dismech entry and is represented here only as a spectrum pointer.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"optic fissure closure defect, it is referred to as colobomatous microphthalmia"

Defines colobomatous microphthalmia as microphthalmia plus a fissure-closure defect.

Posterior microphthalmia / nanophthalmia MONDO:0005514

Reduced total axial length with normal anterior-segment dimensions (posterior microphthalmia), or the related nanophthalmia phenotype of extreme hyperopia, microcornea and frequent angle-closure glaucoma. Genetically distinct from severe A/M, being associated with MFRP (MCOP5) and PRSS56 (MCOP6).

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Nanophthalmia is a particular form of reduced eye size characterized by extreme hyperopia,"

Distinguishes nanophthalmia and posterior microphthalmia from severe anophthalmia-microphthalmia.

Isolated microphthalmia 1 (OMIM:251600) MONDO:0009631

Numbered isolated-microphthalmia locus mapped to chromosomal region 14q32. MONDO records no causal gene for this locus; verified via OAK, so no gene is asserted here.

Isolated microphthalmia 2 — VSX2 (OMIM:610093) MONDO:0012409

VSX2 hgnc:1975

Autosomal recessive isolated microphthalmia caused by biallelic VSX2 (CHX10) variants; gene assignment verified from the MONDO disease_series_by_gene definition.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"VSX2 is expressed during optic vesicle formation, and its"

Places VSX2 in optic-vesicle-stage eye development, the mechanism underlying this recessive locus.

Isolated microphthalmia 3 — RAX (OMIM:611038) MONDO:0012604

RAX hgnc:18662

Autosomal recessive isolated microphthalmia/anophthalmia caused by biallelic RAX variants; gene assignment verified from MONDO.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Biallelic mutations have been identified in 7 families with a bilateral and severe ocular A/M phenotype"

Documents biallelic RAX variants in bilateral severe A/M families, the MCOP3 phenotype.

Isolated microphthalmia 4 — GDF6 (OMIM:613094) MONDO:0013130

GDF6 hgnc:4221

Isolated microphthalmia associated with GDF6, a BMP-family ligand; gene assignment verified from MONDO.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Variants in these genes account for 1.7% and 1% of A/M and coloboma patients screened for GDF3 or GDF6 mutations, respectively"

Quantifies the GDF6 contribution to A/M and coloboma.

Isolated microphthalmia 5 — MFRP (OMIM:611040) MONDO:0012605

MFRP hgnc:18121

Posterior microphthalmia/nanophthalmos with retinitis pigmentosa, foveoschisis and optic disc drusen, caused by MFRP variants; gene assignment verified from the MONDO RO:0004003 relation to HGNC:18121.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"In humans, biallelic mutations in MFRP were first associated with nanophthalmia (Sundin et al. 2005)."

Documents biallelic MFRP variants causing nanophthalmia and posterior microphthalmia.

Isolated microphthalmia 6 — PRSS56 (OMIM:613517) MONDO:0013293

PRSS56 hgnc:39433

Posterior microphthalmos and nanophthalmos caused by PRSS56 variants; gene assignment verified from MONDO.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"cause autosomal recessive posterior microphthalmia and nanophthalmia in"

Documents biallelic PRSS56 variants causing recessive posterior microphthalmia and nanophthalmia.

Isolated microphthalmia 7 — GDF3 (OMIM:613704) MONDO:0013377

GDF3 hgnc:4218

Isolated microphthalmia caused by GDF3 variants, reported with ocular and skeletal anomalies; gene assignment verified from MONDO.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"All of the pathogenic variants reported to date for GDF3 and GDF6 are heterozygous missense changes"

Documents the heterozygous missense GDF3 variants underlying this locus.

Isolated microphthalmia 8 — ALDH1A3 (OMIM:615113) MONDO:0014050

ALDH1A3 hgnc:409

Autosomal recessive anophthalmia/microphthalmia caused by biallelic ALDH1A3 variants that impair retinaldehyde dehydrogenase-mediated retinoic acid synthesis; gene assignment verified from MONDO.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Mutations in ALDH1A3 are a frequent cause of A/M"

Documents ALDH1A3 as a frequent cause of A/M in consanguineous pedigrees.

Numbered microphthalmia-with-coloboma loci (MCOPCB1-13)

The parallel numbered series for microphthalmia with coloboma, all MONDO children of MONDO:0000170. Gene assignments re-derived from MONDO: MCOPCB3 VSX2, MCOPCB5 SHH, MCOPCB7 ABCB6, MCOPCB9 TENM3, MCOPCB10 RBP4, MCOP/CB11 FZD5, MCOP/CB13 NHEJ1. MONDO has no MCOPCB12 term at all, and records no causal gene for MCOPCB1 (X-linked), MCOPCB2, MCOPCB4, MCOPCB6 (digenic) or MCOPCB8. Detailed curation of this arm lives in the `Microphthalmia_with_Coloboma` entry.

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Pathophysiology

Eye Field Transcription Factor Network Dosage Loss

The proximal molecular lesion in most genetically explained cases is loss of functional dosage of a transcription factor that specifies and maintains the anterior neural-plate eye field. SOX2 and OTX2 act as dosage-sensitive hubs that bind regulatory elements of downstream eye-field genes including RAX and PAX6; heterozygous loss-of-function variants, whole-gene deletions and regulatory or copy-number lesions all reduce effective dosage. Biallelic loss of RAX, VSX2 or FOXE3 removes the corresponding node outright. Because these factors act sequentially and combinatorially, the developmental stage at which the network first fails, rather than the identity of the gene alone, sets the severity of the resulting malformation.

SOX2 hgnc:11195 OTX2 hgnc:8522 PAX6 hgnc:8620 MAB21L2 hgnc:6758 FOXE3 hgnc:3808

eye field specification GO:0060898 ↓ DECREASED embryonic camera-type eye formation GO:0060900 ↓ DECREASED

optic vesicle UBERON:0004128

Downstream

Failure of Optic Vesicle Evagination Loss of eye-field specification prevents the eye-forming region from evaginating into paired optic vesicles.

Failure of Optic Cup Invagination and Growth Partial dosage loss permits vesicle formation but impairs subsequent invagination and growth.

Failure of Optic Fissure Closure Reduced dosage of the same network perturbs ventral optic-cup patterning required for fissure fusion.

Retinal Progenitor Specification Failure and RPE Fate Shift Loss of VSX2, itself a member of this eye-field network, removes the neural-retina specification and RPE-repression node.

Extraocular Pleiotropy of Eye Field Transcription Factors The same dosage lesion acts in the non-ocular expression domains of SOX2, OTX2 and RAX, producing extraocular disease.

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"This process of eye formation is directed by a network of genes, and any disruption of these"

States that a gene network directs eye formation and that its disruption produces A/M and coloboma.

PMID:30762128 SUPPORT Human Clinical

"major gene responsible for A/M is SOX2, accounting for 10-15% of affected individuals, usually those"

Identifies SOX2 dosage loss as the single commonest molecular lesion.

Failure of Optic Vesicle Evagination

STEP 1 OF THE THREE-STEP SPINE. During neurulation (4th week of human gestation) the eye-forming region of the anterior neural plate evaginates laterally, splitting the single eye field into right and left optic vesicles. Complete failure of this earliest morphogenetic step — through lack of induction at the primitive neural tube, failure of the optic pit to enlarge, or (in some models) secondary regression of an already-formed structure — aborts globe formation altogether. This is the step whose failure yields anophthalmia, and it explains why histologically detectable vestigial ocular tissue is variably found in anophthalmic sockets.

retinal progenitor cell CL:0002672

RAX hgnc:18662

optic vesicle formation GO:0003403 ↓ DECREASED optic vesicle morphogenesis GO:0003404 ↓ DECREASED

optic vesicle UBERON:0004128

Downstream

Absent or Severely Reduced Globe Formation Failure of the earliest evagination step aborts globe formation, producing anophthalmia.

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"eye-forming region evaginates laterally, splitting the eye field into right and left optic vesicles."

Defines the evagination step whose failure is modelled by this node.

PMID:30762128 SUPPORT Human Clinical

"may result from a lack of induction at the level of the primitive neural tube or a failure of the optic pit"

States the proposed mechanism by which failure at this earliest step produces anophthalmia.

Failure of Optic Cup Invagination and Growth

STEP 2 OF THE THREE-STEP SPINE. Extension of the optic vesicle drives invagination of its distal surface, partitioning it into proximal (optic stalk) and distal (optic cup) territories; the two layers of the cup become the neural retina and the retinal pigment epithelium, while the overlying surface ectoderm is induced to form the lens placode. Partial rather than complete failure at this step — impaired cell movements integral to invagination, failure of lens induction, or defective early retinal differentiation — yields a globe that forms but remains small. The BMP-family ligands GDF3 and GDF6 pattern this step, and heterozygous missense variants in either produce ocular anomalies ranging from bilateral anophthalmia to unilateral coloboma. This is the step whose failure yields microphthalmia rather than anophthalmia.

GDF6 hgnc:4221 GDF3 hgnc:4218

optic cup formation GO:0003408 ↓ DECREASED optic cup morphogenesis GO:0002072 ↓ DECREASED lens development GO:0002088 ↓ DECREASED

optic cup UBERON:0003072 lens placode UBERON:0003073

Downstream

Absent or Severely Reduced Globe Formation Impaired invagination and growth of the optic cup produce a small globe.

Increased Apoptosis and Reduced Proliferation in the Developing Optic Vesicle Disrupted optic-cup morphogenesis is executed cellularly as excess apoptosis with reduced progenitor proliferation.

Anterior and Posterior Segment Dysgenesis Failure of lens induction and early retinal differentiation produces associated segment anomalies.

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"The two layers of the optic cup form the neural and pigmented retina."

Defines the invagination step and the tissues it generates.

PMID:30762128 SUPPORT Human Clinical

"anophthalmia can occur following failure of lens induction (Inoue et al. 2007), early retinal"

Identifies lens-induction and early-retinal-differentiation failure at this step as mechanisms of A/M.

Failure of Optic Fissure Closure

STEP 3 OF THE THREE-STEP SPINE. Invagination of the optic cup is asymmetric, leaving a ventral furrow — the optic fissure — running from the cup into the optic stalk, through which the hyaloid artery enters. The nasal and temporal edges of this fissure must fuse during the 7th week of human development. Failure of this epithelial fusion produces coloboma, which may involve iris, retina, choroid and optic nerve; when it co-occurs with a small globe the result is colobomatous microphthalmia. Retinoic acid receptor signalling regulates fissure closure through independent actions on the ventral optic cup and on the neural-crest-derived periocular mesenchyme. NOTE: the gene-level detail of this arm is curated in the separate `Microphthalmia_with_Coloboma` entry (MONDO:0000170).

periocular mesenchymal cell (neural crest derived) CL:0000333

closure of optic fissure GO:0061386 ↓ DECREASED

optic fissure UBERON:0005412

Downstream

Coloboma Failure of nasal-temporal fissure fusion leaves a persistent ventral tissue defect.

Anterior and Posterior Segment Dysgenesis A persistent fissure defect disrupts normal iris, retinal, choroidal and optic-nerve architecture.

Show evidence (2 references)

PMID:20301552 SUPPORT Human Clinical

"the ocular malformations that result from failure of closure of the optic"

GeneReviews states that coloboma results from failure of closure of the optic fissure.

PMID:21555593 SUPPORT Model Organism

"RAR signaling regulates choroid fissure closure in zebrafish by acting on both the ventral optic cup and the POM"

Zebrafish evidence that retinoic acid receptor signalling controls fissure closure via two independent tissue compartments.

Retinoic Acid Signalling Deficiency

A coherent sub-pathway converging on the same morphogenetic steps. Vitamin A (retinol) is delivered to the embryo bound to RBP4 and taken up by the membrane receptor STRA6; ALDH1A3 (retinaldehyde dehydrogenase 3) oxidises retinaldehyde to all-trans retinoic acid; RARB transduces the signal in the nucleus. Loss of any step depletes retinoic acid in the ventral optic cup and periocular mesenchyme, impairing optic-cup morphogenesis and fissure closure. Biallelic ALDH1A3 variants account for approximately 11% of recessively inherited severe developmental eye anomalies. This node is also the point of convergence for the non-genetic retinoid causes (maternal vitamin A deficiency, exogenous retinoid teratogens), which perturb the same pathway from the opposite direction — both loss and gain of retinoic acid signalling cause structural eye defects.

ALDH1A3 hgnc:409

retinoic acid biosynthetic process GO:0002138 ↓ DECREASED

Downstream

Failure of Optic Cup Invagination and Growth Retinoic acid depletion impairs ventral optic-cup morphogenesis and growth.

Failure of Optic Fissure Closure Retinoic acid receptor signalling is required in both the ventral optic cup and the periocular mesenchyme for fissure closure.

Show evidence (3 references)

PMID:36997679 SUPPORT Human Clinical

"Biallelic pathogenic variants in ALDH1A3 are responsible for approximately 11%"

Quantifies the contribution of the retinoic-acid-synthesis arm to recessive severe eye anomalies.

PMID:21555593 SUPPORT Model Organism

"Retinoic acid receptor (RAR) signaling is required for morphogenesis of the ventral optic cup and closure of the choroid fissure"

Establishes the requirement for retinoic acid receptor signalling in the two morphogenetic steps this node feeds.

PMID:30762128 SUPPORT Human Clinical

"STRA6, RARB, ALDH1A3 and RBP4. Both loss and gain of retinoic acid signaling cause structural defects"

Names the four retinoid-pathway genes and states the bidirectional dose sensitivity of the pathway.

Retinal Progenitor Specification Failure and RPE Fate Shift

VSX2 (CHX10) is expressed from optic-vesicle stage in the presumptive neural retina, where it drives retinal-progenitor proliferation and represses the retinal-pigment-epithelium programme. Biallelic VSX2 loss shifts the neural-retina/RPE boundary toward RPE identity and depletes the progenitor pool that would otherwise expand the optic cup, producing bilateral microphthalmia. The mutations reported in recessive microphthalmia disrupt either the homeodomain or the conserved CVC motif required for DNA binding and repression.

retinal progenitor cell CL:0002672 retinal pigment epithelial cell CL:0002586

VSX2 hgnc:1975

neural retina development GO:0003407 ↓ DECREASED retinal pigment epithelium development GO:0003406 ↑ INCREASED

Downstream

Failure of Optic Cup Invagination and Growth Loss of the retinal progenitor pool prevents the optic cup from expanding to normal size.

Show evidence (3 references)

PMID:21976963 SUPPORT Human Clinical

"This p.G223A mutation affects the conserved CVC motif that was shown to be important for DNA binding and repression activities of VSX2."

Links the human recessive microphthalmia mutations to loss of VSX2 DNA-binding and repressive function.

PMID:30762128 SUPPORT Human Clinical

"VSX2 is expressed during optic vesicle formation, and its"

Places VSX2 action at the optic-vesicle stage of the developmental spine.

PMID:25927996 SUPPORT Model Organism

"We show that Vsx2 maintains retinal identity in part through the cell-autonomous repression of the retinal pigment epithelium determinant Mitf"

Mouse-chimera evidence that Vsx2 maintains neural-retina identity by cell-autonomously repressing the RPE determinant MITF, the fate shift modelled by this node.

Increased Apoptosis and Reduced Proliferation in the Developing Optic Vesicle

A convergent cellular execution mechanism identified in patient-derived induced-pluripotent-stem-cell optic vesicles from unrelated microphthalmia patients: optic-vesicle diameter is significantly reduced from day 20, with upregulation of apoptosis-initiating and extracellular-matrix genes, increased apoptosis and decreased proliferation. Caspase-8 inhibition reduced apoptosis in one patient model, identifying a shared and potentially tractable downstream node distinct from the specific upstream genetic lesion.

retinal progenitor cell CL:0002672

apoptotic process GO:0006915 ↑ INCREASED cell population proliferation GO:0008283 ↓ DECREASED

Downstream

Absent or Severely Reduced Globe Formation Excess apoptosis with reduced proliferation depletes the cell mass available to build a normal-sized globe.

Show evidence (2 references)

PMID:38821055 SUPPORT In Vitro

"Increased apoptosis was observed in microphthalmia OVs with reduced phospho-histone 3 (pH3+) cells confirming decreased cell proliferation at day 35."

Patient-derived iPSC optic vesicles demonstrate the apoptosis and proliferation imbalance modelled by this node.

PMID:38821055 SUPPORT In Vitro

"These data reveal shared pathophysiological mechanisms contributing to a microphthalmia phenotype."

Supports treating this cellular imbalance as a convergent mechanism across genetically distinct microphthalmia.

Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis

A minority of A/M is non-genetic. The same three morphogenetic steps are vulnerable to first-trimester environmental insult: gestationally acquired infection (the strongest environmental evidence), maternal vitamin A deficiency, exposure to X-rays, solvent misuse, and thalidomide. Exogenous retinoids act on the same retinoic-acid node as the STRA6/ALDH1A3/RARB genetic lesions. Because the critical window is embryonic there is no postnatal trigger, and the malformation itself is not transmissible.

Downstream

Failure of Optic Cup Invagination and Growth First-trimester teratogenic or infectious insult perturbs optic-cup morphogenesis during the critical window.

Retinoic Acid Signalling Deficiency Maternal vitamin A deficiency and retinoid teratogens perturb embryonic retinoic acid availability directly.

Show evidence (1 reference)

PMID:18039390 SUPPORT Human Clinical

"The strongest evidence appears to be with gestational-acquired infections, but may"

Ranks gestational infection first among the recognised environmental causes of A/M.

Absent or Severely Reduced Globe Formation

The convergent structural outcome of all upstream routes: a globe that is absent, or whose total axial length is at least two standard deviations below the age-adjusted mean (<21 mm in adults, <14 mm in newborns). Severe microphthalmia is defined by a corneal diameter under 4 mm with total axial length under 10 mm at birth or under 12 mm after one year. The structural deficit is permanent and does not remit; asymmetric and unilateral involvement is common, implying differences in developmental robustness and buffering between the two sides. A mechanistically separate route to a small globe is restricted axial growth with a normal anterior segment (posterior microphthalmia and nanophthalmia), caused by biallelic MFRP or PRSS56 variants.

MFRP hgnc:18121 PRSS56 hgnc:39433

camera-type eye development GO:0043010 ↓ DECREASED

eyeball of camera-type eye UBERON:0010230

Downstream

Anophthalmia Complete failure of globe formation presents clinically as anophthalmia.

Microphthalmia Partial failure of globe growth presents clinically as microphthalmia.

Microcornea Reduced globe size is accompanied by a reduced corneal diameter.

Failure of Orbital and Periocular Growth The absent or small globe fails to provide the mechanical stimulus that drives orbital expansion.

Congenital Visual Deprivation Absent or malformed ocular tissue prevents formation of a functional visual pathway.

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"deviations (SD) below the age-adjusted population mean; < 21 mm in adults and < 14 mm in newborns"

Provides the quantitative structural definition of the convergent outcome node.

PMID:30762128 SUPPORT Human Clinical

"Asymmetric involvement is common, suggesting differences in robustness and buffering mechanisms between the two sides."

Notes the asymmetry of involvement characteristic of this convergent outcome.

Failure of Orbital and Periocular Growth

Postnatal expansion of the bony orbit, conjunctival cul-de-sac and palpebral fissure is driven mechanically by growth of the globe. When the globe is absent or very small this stimulus is lost, and the orbit, eyelids and midface on the affected side remain hypoplastic, producing progressive facial asymmetry. This is the rationale for the principal therapeutic intervention in this disorder — serial conformer-assisted socket expansion begun in infancy, which in a case series increased mean lid length by 90.9% in anophthalmia and 31.3% in microphthalmia.

orbit of skull UBERON:0001697

Downstream

Orbital and Palpebral Fissure Hypoplasia Loss of the globe-derived growth stimulus leaves the orbit and palpebral fissure underdeveloped.

Show evidence (2 references)

PMID:20301552 SUPPORT Human Clinical

"an ocularist can start shortly after birth to expand the palpebral fissures"

GeneReviews implies globe-dependent orbital growth by describing the need for mechanical expansion when the globe is absent; the causal dependency itself is not stated explicitly, so this is scored PARTIAL.

PMID:36257503 SUPPORT Human Clinical

"Percentage increases in lid length were 90.9%, 61.2%, and 31.3% in anophthalmia, clinical anophthalmia, and microphthalmia, respectively"

The conformer series quantifies the growth deficit that mechanical expansion corrects.

Anterior and Posterior Segment Dysgenesis

In complex microphthalmia the same morphogenetic failures that reduce globe size also disrupt differentiation of individual ocular structures, producing anterior-segment anomalies (Axenfeld-Rieger anomaly, Peters anomaly, sclerocornea, cataract) and posterior-segment anomalies (persistent primitive vitreous, chorioretinal coloboma, retinal dysplasia). In a prospective MAC cohort 44% had complex ocular features beyond the MAC phenotype itself.

eyeball of camera-type eye UBERON:0010230

Downstream

Cataract Disrupted lens induction and differentiation produces congenital lens opacity.

Sclerocornea Failure of anterior-segment differentiation produces an opaque, sclera-like cornea.

Glaucoma Anterior-segment dysgenesis obstructs aqueous outflow and raises intraocular pressure.

Retinal detachment Dysplastic retina and abnormal vitreous predispose to later retinal detachment.

Show evidence (1 reference)

PMID:36192130 SUPPORT Human Clinical

"from 44 unrelated families found 44% had additional ocular features (complex)"

Quantifies the frequency of additional complex ocular features in a prospective MAC cohort.

Extraocular Pleiotropy of Eye Field Transcription Factors

THE HONESTY NODE FOR THE "ISOLATED" LABEL. SOX2, OTX2 and RAX are not eye-restricted. SOX2 is required for pluripotency and multiple early developmental programmes; OTX2 is expressed in the posterior pituitary, retina, ear, thalamus and choroid plexus during human embryogenesis; RAX patterns the ventral forebrain and hypothalamus. Consequently the same dosage lesion that produces A/M frequently produces psychomotor delay, ventriculomegaly and corpus-callosum hypoplasia, hypogonadism and pituitary dysfunction, growth and renal anomalies, and — in the AEG/MCOPS3 form — oesophageal atresia. SOX2 variants have been reported in individuals with structurally normal eyes, and truncating RAX variants have caused anophthalmia with hypopituitarism, diabetes insipidus and cleft palate. A disorder labelled "isolated" is therefore isolated only until it is looked for elsewhere.

Downstream

Global developmental delay Extraocular action of the same transcription factors impairs neurodevelopment.

Hypopituitarism OTX2 and RAX act in pituitary and hypothalamic development.

Hypogonadism Pituitary and gonadal-axis involvement follows from the same dosage lesion.

Esophageal atresia SOX2 loss disrupts foregut separation, the AEG/MCOPS3 association.

Hypoplasia of the corpus callosum SOX2 loss produces midline forebrain malformation.

Show evidence (3 references)

PMID:30762128 SUPPORT Human Clinical

"The most common extraocular features are psychomotor"

Introduces the canonical extraocular feature list for SOX2-related A/M.

PMID:33950863 SUPPORT In Vitro

"During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary."

Demonstrates the non-ocular expression domains that underlie OTX2 extraocular disease.

PMID:37163579 SUPPORT Human Clinical

"Our patients provide further evidence for broadening the phenotypic spectrum of SOX2 mutations and"

Direct evidence that the SOX2 phenotype is not confined to the eye, undermining a strictly ocular reading of the isolated label.

Congenital Visual Deprivation

Absence or severe malformation of the globe prevents formation of a normal retinal image and, in bilateral disease, of a functional visual pathway. Visual outcome depends principally on laterality, residual retinal and optic-nerve development and the status of the fellow eye. Bilateral severe disease produces lifelong blindness; unilateral disease may preserve useful vision but leaves the fellow eye at risk from amblyopia and injury. In a paediatric A/M cohort 10 of 35 children were totally blind or had light perception only.

Downstream

Visual impairment Loss of ocular tissue directly reduces visual function.

Blindness Bilateral severe disease abolishes form vision.

Amblyopia In unilateral disease the fellow eye is at risk of deprivation and refractive amblyopia.

Show evidence (1 reference)

PMID:35105264 SUPPORT Human Clinical

"Ten cases were totally blind or had light perception."

Quantifies the visual outcome of the convergent structural deficit.

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Pathograph

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Phenotypes

Digestive 1

Esophageal atresia VERY_RARE HP:0002032

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Rarely patients may also display esophageal atresia"

Documents oesophageal atresia as a rare extraocular feature of SOX2-related A/M, supporting the VERY_RARE band.

Endocrine 1

Hypogonadism HP:0000135

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"hypogonadism and growth retardation, possibly related to pituitary anomalies, and renal"

Lists hypogonadism among the common extraocular features of SOX2-related A/M.

Eye 9

Microphthalmia VERY_FREQUENT HP:0000568

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"Microphthalmia refers to a decreased size of the eye"

Defines the phenotype and its quantitative threshold.

PMID:36997679 SUPPORT Human Clinical

"All affected individuals had bilateral anophthalmia/microphthalmia (A/M)"

Supports the VERY_FREQUENT band — A/M was present in every affected individual across seven ALDH1A3 families.

Coloboma HP:0000589

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"the ocular malformations that result from failure of closure of the optic"

Directly ties the coloboma phenotype to the third developmental step.

Microcornea HP:0000482

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Microphthalmia is classed as severe if the corneal diameter is < 4 mm"

Establishes reduced corneal diameter as part of the severe microphthalmia phenotype.

Cataract HP:0000518

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"sclerocornea and cataract) or of the posterior segment (persistence of primitive vitreous, chorioretinal"

Lists cataract among the anterior-segment anomalies defining complex microphthalmia.

Sclerocornea HP:0000647

Show evidence (1 reference)

PMID:29136273 SUPPORT Human Clinical

"associated with recessively inherited primary aphakia, sclerocornea and microphthalmia."

Documents the recessive FOXE3 phenotype of primary aphakia, sclerocornea and microphthalmia.

Glaucoma HP:0000501

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Nanophthalmia is a particular form of reduced eye size characterized by extreme hyperopia, microcornea and frequently glaucoma."

Documents glaucoma as a recurrent complication in the reduced-eye-size phenotype.

Retinal detachment OCCASIONAL HP:0000541

Show evidence (1 reference)

PMID:36192130 SUPPORT Human Clinical

"from 44 unrelated families found 44% had additional ocular features (complex)"

The prospective cohort from which the 9% retinal-detachment figure derives; the abstract quantifies the complex-ocular-feature denominator rather than the detachment rate itself, so this is scored PARTIAL.

Visual impairment FREQUENT HP:0000505

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"frequently responsible for severe visual impairment, accounting for approximately 3% to 12% of visual"

Documents severe visual impairment as the dominant functional outcome; the review's qualitative "frequently" maps to the FREQUENT band.

Blindness OCCASIONAL HP:0000618

Show evidence (1 reference)

PMID:35105264 SUPPORT Human Clinical

"Ten cases were totally blind or had light perception."

Supports the OCCASIONAL band (10/35 = 29%, within the 5-29% range) in a paediatric A/M cohort.

Nervous System 2

Global developmental delay OCCASIONAL HP:0001263

Show evidence (1 reference)

PMID:36192130 SUPPORT Human Clinical

"34% had systemic involvement, most"

Quantifies systemic involvement, most frequently intellectual/developmental delay, in a prospective MAC cohort.

Hypoplasia of the corpus callosum OCCASIONAL HP:0002079

Show evidence (1 reference)

PMID:35105264 SUPPORT Human Clinical

"Neuroimaging demonstrated pathology in 14/20 cases with corpus callosum dysgenesis (6/20) being the most common."

Documents corpus callosum dysgenesis as the commonest neuroimaging finding in a paediatric A/M cohort (6/20); the conservative OCCASIONAL band is used.

Other 4

Anophthalmia HP:0000528

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"Anophthalmia refers to complete absence of the globe in the presence of ocular adnexa"

GeneReviews clinical definition of the defining phenotype.

Orbital and Palpebral Fissure Hypoplasia Blepharophimosis HP:0000581

Show evidence (1 reference)

PMID:36257503 SUPPORT Human Clinical

"The mean initial lid lengths in anophthalmia, clinical anophthalmia,"

Quantifies the palpebral fissure shortening produced by absent globe growth.

Amblyopia HP:0000646

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"Protection of the healthy eye in those with"

GeneReviews management guidance implying the risk to the fellow eye in unilateral disease; the abstract does not name amblyopia explicitly, so this is scored PARTIAL.

Hypopituitarism HP:0040075

Show evidence (2 references)

PMID:33950863 SUPPORT Human Clinical

"Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities"

Identifies OTX2 haploinsufficiency in congenital hypopituitarism patients with eye abnormalities.

PMID:30811539 SUPPORT Human Clinical

"We report the case of a child with anophthalmia, congenital"

Documents hypopituitarism co-occurring with anophthalmia in a RAX-diagnosed patient.

🧬

Genetic Associations

SOX2

Gene: SOX2 hgnc:11195 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"SOX2 pathogenic variants, including whole gene deletions, are present in 10-15% of all A/M patients"

Quantifies the SOX2 contribution to A/M.

PMID:30450772 SUPPORT Human Clinical

"Heterozygous loss-of-function variants in SOX2 are identified in approximately 40% of all"

Quantifies the much higher SOX2 yield specifically in bilateral A/M.

OTX2

Gene: OTX2 hgnc:8522 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:30762128 SUPPORT Human Clinical

"The ocular phenotype of patients with pathogenic OTX2 variants is highly variable even within the"

Documents the marked variability of OTX2 ocular expressivity.

PMID:33950863 SUPPORT Human Clinical

"OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree."

Establishes the coupled pituitary-eye phenotype and the variable penetrance of OTX2 disease.

RAX

Gene: RAX hgnc:18662 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:30811539 SUPPORT Human Clinical

"In humans, homozygous or compound heterozygous RAX mutations have been reported to cause bilateral microphthalmia or anophthalmia without consistent associated features."

Establishes the recessive RAX mechanism and its ocular phenotype.

VSX2

Gene: VSX2 hgnc:1975 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:21976963 SUPPORT Human Clinical

"Homozygous mutations in VSX2 were identified in two out of five"

Directly documents biallelic VSX2 variants in consanguineous families with isolated microphthalmia.

ALDH1A3

Gene: ALDH1A3 hgnc:409 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:36997679 SUPPORT Human Clinical

"All affected individuals had bilateral anophthalmia/microphthalmia (A/M), three with additional intellectual or developmental delay, one with autism and seizures and three with facial dysmorphic features."

Establishes the fully penetrant ocular phenotype and the variable neurodevelopmental extension.

PMID:24024553 SUPPORT Human Clinical

"we identified a novel homozygous missense mutation in ALDH1A3 using exome sequencing"

Independent confirmation of the recessive ALDH1A3 mechanism.

FOXE3

Gene: FOXE3 hgnc:3808 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:29136273 SUPPORT Human Clinical

"This review demonstrates that correlations exist between the mutation type, mode of"

Establishes the dual dominant/recessive FOXE3 mechanism and its genotype-phenotype structure.

PAX6

Gene: PAX6 hgnc:8620 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:26130484 SUPPORT Human Clinical

"A novel heterozygous likely pathogenic variant in PAX6, c.767T>C,"

Documents a pathogenic PAX6 variant in probands with bilateral microphthalmia and coloboma.

MAB21L2

Gene: MAB21L2 hgnc:6758 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:36192130 SUPPORT Human Clinical

"New phenotypic associations were found for FOXE3 (bilateral sensorineural hearing loss) and MAB21L2 (unilateral microphthalmia)."

Documents MAB21L2 as a causal MAC gene with a newly described unilateral microphthalmia association.

GDF6

Gene: GDF6 hgnc:4221 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"Variants in these genes account for 1.7% and 1% of A/M and coloboma patients screened for GDF3 or GDF6 mutations, respectively"

Quantifies the GDF6 (1%) and GDF3 (1.7%) contributions to screened A/M and coloboma cohorts.

GDF3

Gene: GDF3 hgnc:4218 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"All of the pathogenic variants reported to date for GDF3 and GDF6 are heterozygous missense changes"

Establishes the heterozygous missense mechanism shared by GDF3 and GDF6.

MFRP

Gene: MFRP hgnc:18121 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"In humans, biallelic mutations in MFRP were first associated with nanophthalmia (Sundin et al. 2005)."

Documents the recessive MFRP mechanism and its nanophthalmia and posterior microphthalmia phenotype.

PRSS56

Gene: PRSS56 hgnc:39433 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"cause autosomal recessive posterior microphthalmia and nanophthalmia in"

Documents the recessive PRSS56 mechanism and its posterior microphthalmia and nanophthalmia phenotype.

Copy-number and chromosomal variants

relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:27552085 SUPPORT Human Clinical

"Chromosome analysis was performed in 36.1% of the cohort, and 14.7% of cases had an abnormal karyotype."

The Danish cohort reports an abnormal karyotype in 14.7% of those analysed, quantifying the chromosomal contribution.

💊

Medical Actions

Serial conformer-assisted socket expansion

Action: Therapeutic Procedure NCIT:C49236

The principal disease-directed intervention. Because orbital, conjunctival and eyelid growth is normally driven by the expanding globe, an ocularist fits conformers of progressively increasing size starting shortly after birth to expand the palpebral fissure, conjunctival cul-de-sac and bony orbit. In a 24-orbit case series with a mean of 7 conformer exchanges over 51 months, good outcomes were achieved in 18 orbits (75%) and fair outcomes in 6 (25%), with unilateral cases reaching a mean final lid length of 22.3 mm against 23.5 mm in the normal contralateral eye.

Mechanism Target:

BYPASSES Failure of Orbital and Periocular Growth — Conformers supply mechanically the expansile stimulus that the absent or small globe cannot, driving orbital and palpebral growth by an external route rather than restoring globe development.

Target Phenotypes: Blepharophimosis HP:0000581

Show evidence (2 references)

PMID:36257503 SUPPORT Human Clinical

"Good outcomes were achieved in 18 orbits (75%); fair outcomes, in 6 (25%) cases."

The case series reports good outcomes in 18 of 24 orbits (75%) after conformer-assisted socket expansion.

PMID:20301552 SUPPORT Human Clinical

"an ocularist can start shortly after birth to expand the palpebral fissures"

GeneReviews management recommendation establishing timing and rationale.

Ocular prosthesis

Action: Therapeutic Procedure NCIT:C49236

Fitting of an ocular prosthesis over the socket or a microphthalmic globe. GeneReviews states directly that prosthetic intervention is appropriate for those with severe microphthalmia and anophthalmia; it is the most universal intervention in this disorder, addressing both cosmesis and, together with conformers, socket volume. In a prospective MAC cohort most patients did not require a customised prosthesis, so the need is individualised rather than universal across the whole spectrum.

Mechanism Target:

BYPASSES Failure of Orbital and Periocular Growth — A prosthesis occupies and maintains socket volume in place of the absent or hypoplastic globe.

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"Prosthetic intervention is appropriate for those with severe microphthalmia and anophthalmia."

GeneReviews management recommendation for prosthetic intervention.

Oculoplastic and orbital reconstructive surgery

Action: Ophthalmologic Surgical Procedure NCIT:C15331

Surgical intervention for severe sockets, orbital cysts and prosthetic support. GeneReviews advises that an oculoplastic surgeon determine the most suitable options after age six months, when postnatal orbital growth can be assessed, and before orbital dimensions become fixed — after which far more extensive reconstruction is required. This timing constraint is the key management point.

Mechanism Target:

BYPASSES Failure of Orbital and Periocular Growth — Orbital reconstruction and implants substitute surgically for the missing globe-driven expansion of the socket.

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"An oculoplastic surgeon can help determine the most suitable options for"

GeneReviews surgical timing guidance for orbital reconstruction.

Low-vision rehabilitation and early developmental intervention

Action: Rehabilitation NCIT:C15315

Children with reduced vision benefit from visual aids and visual resources, together with early intervention to optimise psychomotor development, education, life skills and mobility. Orientation and mobility training is central for bilateral visual loss. Quality of life is measurably reduced: median parent-reported PedsQL total score was 52.4 in affected children aged 2-12.

Target Phenotypes: Visual impairment HP:0000505

Show evidence (2 references)

PMID:20301552 SUPPORT Human Clinical

"Children with reduced vision may benefit from visual aids and other visual resources as well as early"

GeneReviews rehabilitation recommendation.

PMID:35105264 SUPPORT Human Clinical

"The median total PedsQL score of parent reports for ages 2-12 was 52.4 (range 22.6-100)."

Quantifies the quality-of-life impairment that rehabilitation addresses.

Protection of the fellow eye

Action: Supportive Care NCIT:C15747

In unilateral disease the unaffected eye carries the individual's entire visual function, so protective polycarbonate eyewear, prompt refraction and amblyopia treatment are explicitly recommended. This is the highest-yield, lowest-cost intervention in unilateral A/M.

Target Phenotypes: Amblyopia HP:0000646

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"Protection of the healthy eye in those with"

GeneReviews management recommendation for unilateral disease.

Genetic counselling and molecular diagnosis

Action: Genetic Counseling NCIT:C15240

Molecular testing identifies a genetic cause in 80% of individuals with bilateral anophthalmia or severe microphthalmia and up to 20% of all MAC individuals, and should combine sequencing with gene-targeted deletion/duplication analysis and chromosomal microarray. Real-world yields are meaningful in unilateral as well as bilateral disease (33% in each group in a prospective cohort), so testing should not be restricted to bilateral cases. Counselling must address de novo occurrence, incomplete penetrance, variable expressivity and germline mosaicism, which together mean recurrence risk after an apparently de novo diagnosis is not zero.

Show evidence (2 references)

PMID:20301552 SUPPORT Human Clinical

"can identify a genetic cause in 80% of individuals with"

GeneReviews diagnostic-yield figure underpinning the testing recommendation.

PMID:36192130 SUPPORT Human Clinical

"a molecular diagnostic rate of 33% for both bilateral and unilateral cohorts"

Supports extending genetic testing to unilateral cases.

Management of secondary ocular complications

Action: Ophthalmologic Surgical Procedure NCIT:C15331

Remediable pathology in the malformed or fellow eye should be treated actively: cataract extraction, glaucoma control, and retinal-detachment repair. Retinal detachment occurred in 9% of a prospective MAC cohort and presented from the first to the third decade, so lifelong surveillance rather than a fixed discharge point is appropriate.

Target Phenotypes: Cataract HP:0000518 Glaucoma HP:0000501 Retinal detachment HP:0000541

Show evidence (1 reference)

PMID:36192130 SUPPORT Human Clinical

"This study highlights the importance of thorough clinical and molecular phenotyping of MAC patients to provide appropriate multidisciplinary care."

Establishes the multidisciplinary phenotyping and management model within which secondary complications are detected and treated.

🌍

Environmental Factors

Gestationally acquired infection

Congenital infection during the first trimester is the environmental exposure with the strongest evidence for causing A/M. Congenital rubella, toxoplasmosis and cytomegalovirus are classically implicated, and congenital Zika virus infection produced microphthalmia in 2.7% of a systematic review of 479 postnatally examined cases. Infection acts by disrupting or destroying ocular tissue during the developmental window; the malformation itself is not transmissible.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"The strongest evidence appears to be with gestational-acquired infections"

Ranks gestational infection as the best-evidenced environmental cause.

PMID:38350011 SUPPORT Human Clinical

"microphthalmia was reported in 13 cases (13/479, 2.7%)"

Quantifies microphthalmia after congenital Zika virus infection.

Mechanism Target:

TRIGGERS Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis — This node was written to hold the non-genetic minority of cases, and it names gestational infection as the strongest environmental evidence in its own text. Recorded as direct because infection disrupts ocular tissue during the developmental window itself, which is the node's own event rather than something upstream of it. Graded above the other three exposures pointing here, on the source's own ranking rather than a curatorial preference.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"

Ranks gestational infection as the best-evidenced environmental cause, ahead of the other three exposures this entry records. Quoted as the whole sentence, since it is the comparison between the exposures that does the work.

PMID:38350011 SUPPORT Human Clinical

"microphthalmia was reported in 13 cases (13/479, 2.7%)"

Quantifies microphthalmia in 2.7% of postnatally examined congenital Zika cases, giving one infection a measured rate rather than a listing.

Maternal vitamin A deficiency

Insufficient maternal retinol restricts the substrate supply for embryonic retinoic acid synthesis, converging on the same STRA6/ALDH1A3/RARB pathway perturbed by the recessive retinoid-pathway genes. In an Indian case series of children with coloboma, 16% of mothers reported night blindness — a clinical marker of vitamin A deficiency — during the affected pregnancy.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"also include maternal vitamin A deficiency"

Names maternal vitamin A deficiency among the environmental contributors.

PMID:11926054 SUPPORT Human Clinical

"Eleven (16%) mothers had a history of night blindness while pregnant with the affected child"

Provides direct maternal-history evidence linking vitamin A deficiency to congenital eye malformation.

Mechanism Target:

PREDISPOSES Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis — Graded below the infection link into this same node, because the sentence that names both exposures ranks infection first and attaches maternal vitamin A deficiency to a hedged may also include. The mechanistically specific edge for this exposure is the separate one into the retinoic acid node.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"

Names maternal vitamin A deficiency among the environmental contributors, under a hedge the sentence does not apply to gestational infection.

PMID:11926054 SUPPORT Human Clinical

"Eleven (16%) mothers had a history of night blindness while pregnant with the affected child"

Sixteen percent of mothers in a coloboma series reported night blindness during the affected pregnancy. Maternal history rather than any measurement of embryonic signalling.

TRIGGERS Retinoic Acid Signalling Deficiency — The substrate-supply edge, and the reason this exposure is graded differently from the other three: maternal retinol is the source of the embryonic retinoic acid this node is built around, so the intervening step is a known one rather than an unknown. Night blindness in the mother is a clinical marker of the deficiency and not a measurement of embryonic signalling, which is what keeps the evidence partial while the link itself is specific.

Show evidence (1 reference)

PMID:11926054 SUPPORT Human Clinical

"Eleven (16%) mothers had a history of night blindness while pregnant with the affected child"

Maternal night blindness during the affected pregnancy is a clinical marker of the vitamin A deficiency that would limit retinoid substrate at this node.

Teratogenic drug exposure

Thalidomide is the classically documented ocular teratogen in this spectrum. Systemic retinoids (isotretinoin and related compounds) are potent teratogens acting directly on the retinoic-acid signalling node, which is why contraception is mandatory during treatment; retinoid excess and vitamin A deficiency perturb the same pathway from opposite directions. First-trimester medication use was documented in 8% of mothers in an Indian coloboma series.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"exposure to X-rays, solvent misuse and thalidomide exposure"

Names thalidomide among the environmental contributors to A/M.

PMID:11926054 SUPPORT Human Clinical

"seven (8%) took medication during the 1st trimester"

Documents first-trimester medication exposure in mothers of affected children; the specific agents are not all identified, so this is scored PARTIAL.

Mechanism Target:

PREDISPOSES Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis — Thalidomide is named in the review sentence, and first-trimester medication use is documented in a case series without the agents being identified. Not also pointed at the retinoic acid node, although this entry's own description makes that argument for systemic retinoids: no cited sentence names a retinoid, so the edge would rest on the description rather than on evidence.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"

Names thalidomide exposure among the environmental contributors, under the same hedge as vitamin A deficiency.

PMID:11926054 SUPPORT Human Clinical

"seven (8%) took medication during the 1st trimester"

Eight percent of mothers took medication in the first trimester. The agents are not all identified, so this supports an exposure class rather than a drug.

Ionising radiation and solvent exposure

Exposure to X-rays and organic-solvent misuse during early pregnancy are listed among the environmental contributors to A/M, although quantitative effect estimates specific to isolated A/M are not available. Agricultural chemical exposure was reported by 13% of mothers in an Indian coloboma series.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"exposure to X-rays, solvent misuse"

Names ionising radiation and solvent exposure among the recognised environmental contributors.

PMID:11926054 SUPPORT Human Clinical

"11 (13%) reported exposure to agricultural chemicals"

Documents chemical exposure in mothers of children with congenital eye malformation; the association is observational and unadjusted, so this is scored PARTIAL.

Mechanism Target:

PREDISPOSES Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis — X-rays and solvent misuse are listed in the same hedged clause as the other two non-infectious exposures and are graded identically to them. The supporting case-series figure is about agricultural chemicals rather than about either named exposure, which is a further reason this stays partial.

Show evidence (2 references)

PMID:18039390 SUPPORT Human Clinical

"The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"

Names exposure to X-rays and solvent misuse among the environmental contributors.

PMID:11926054 SUPPORT Human Clinical

"11 (13%) reported exposure to agricultural chemicals"

Thirteen percent of mothers reported agricultural chemical exposure. Observational, unadjusted, and about a different chemical class than the two this exposure names.

🔬

Diagnosis

Ophthalmic examination with axial-length biometry

Diagnosis begins with comprehensive paediatric ophthalmological examination: inspection for any globe tissue, corneal diameter, axial length by ultrasound biometry, anterior- and posterior-segment examination where possible, refraction, intraocular pressure and visual behaviour, together with full assessment of the fellow eye. Microphthalmia is confirmed when total axial length is more than 2 SD below the age-adjusted mean (<21 mm in adults, <14 mm in newborns); severe microphthalmia additionally requires a corneal diameter under 4 mm.

Eye Examination NCIT:C38060

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"deviations (SD) below the age-adjusted population mean; < 21 mm in adults and < 14 mm in newborns"

Gives the biometric threshold on which the clinical diagnosis rests.

Orbital and cranial magnetic resonance imaging

Orbital imaging distinguishes a truly absent globe from extreme microphthalmia, an orbital cyst or another orbital lesion, and is particularly indicated in bilateral severe disease, developmental delay, seizures, optic-nerve abnormality or suspected midline and pituitary involvement. In a paediatric A/M cohort neuroimaging was abnormal in 14 of 20 scanned children, corpus callosum dysgenesis being commonest.

Magnetic Resonance Imaging NCIT:C16809

Show evidence (1 reference)

PMID:35105264 SUPPORT Human Clinical

"Neuroimaging demonstrated pathology in 14/20 cases with corpus callosum dysgenesis (6/20) being the most common."

Quantifies the yield of neuroimaging in a paediatric A/M cohort.

Chromosomal microarray analysis

First-tier cytogenetic testing. Chromosomal aberrations are a substantial and easily missed cause: in a Danish national cohort 14.7% of karyotyped cases had an abnormal karyotype, and among the 8.7% who underwent chromosomal microarray a possibly pathogenic copy-number variant was found in 44.4%.

Microarray Analysis NCIT:C18477

Show evidence (1 reference)

PMID:27552085 SUPPORT Human Clinical

"In 8.7% of the cohort, a chromosome microarray analysis was performed, and in 44.4% of cases, a possibly pathogenic copy number variation was observed."

Quantifies the copy-number yield that justifies microarray as a first-tier test.

Exome or genome sequencing

Molecular genetic testing identifies a cause in 80% of individuals with bilateral anophthalmia or severe microphthalmia and up to 20% of all MAC individuals, and should combine sequence analysis with gene-targeted deletion/duplication analysis. Clinical exome sequencing achieved a diagnostic rate starting at 32.3% in a 189-person non-isolated MAC cohort, and a subset of the implicated genes are absent from commercially available ophthalmic gene panels - an argument for exome or genome sequencing rather than panel testing. Real-world yield is comparable in unilateral and bilateral disease (33% each), so testing should not be restricted to bilateral cases.

Whole Exome Sequencing NCIT:C101295

Show evidence (3 references)

PMID:20301552 SUPPORT Human Clinical

"can identify a genetic cause in 80% of individuals with bilateral anophthalmia/severe microphthalmia and in up to 20% of all individuals with an ocular malformation in the MAC spectrum."

GeneReviews diagnostic-yield benchmark.

PMID:38502138 SUPPORT Human Clinical

"We found the efficacy of cES in nonisolated MAC to be between 32.3%"

Contemporary clinical-exome diagnostic rate in a large MAC cohort.

PMID:36192130 SUPPORT Human Clinical

"a molecular diagnostic rate of 33% for both bilateral and unilateral cohorts"

Shows comparable yield in unilateral disease, supporting unrestricted testing.

📊

Prevalence

Denmark, live births 1995-2012

Birth Prevalence 12.0 per 100,000 1–9 per 10,000

Registry-based Danish national cohort (1,174,299 live births). Birth prevalence of microphthalmia or anophthalmia (MO/AO) alone was 1.2 per 10,000 live births, normalised here to 12 per 100,000. The wider MO/AO/coloboma birth prevalence in the same cohort was 3.6 per 10,000 (36 per 100,000).

Show evidence (1 reference)

PMID:27552085 SUPPORT Human Clinical

"the average birth prevalence of MO/AO/coloboma was 3.6/10,000 live births and of MO/AO was"

Population-based Danish birth-prevalence estimate for microphthalmia and anophthalmia.

Worldwide (pooled reviews and birth-defect surveillance)

Birth Prevalence 20.0 per 100,000 (20.0–30.0) 1–9 per 10,000

Pooled estimates place the combined anophthalmia/microphthalmia birth prevalence at up to 2-3 per 10,000 live births (20-30 per 100,000). Estimates vary with surveillance system and with whether coloboma and syndromic cases are included.

Show evidence (2 references)

PMID:35716026 SUPPORT Human Clinical

"Anophthalmia and microphthalmia (A/M) are rare birth defects affecting up to 2"

Contemporary birth-prevalence figure for A/M from a US population-based study.

PMID:18039390 SUPPORT Human Clinical

"of these conditions is up to 30 per 100,000 population"

Upper-bound combined birth prevalence from the Orphanet review.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Isolated Anophthalmia-Microphthalmia Syndrome:

Microphthalmia with coloboma MONDO:0000170

Overlapping Features The immediate MONDO child term (MONDO:0000170) and the fissure-closure arm of the same spectrum, curated in dismech as `Microphthalmia_with_Coloboma`. Distinguished from non-colobomatous A/M by the presence of a demonstrable iris, chorioretinal or optic-disc coloboma. This is a boundary rather than a rival diagnosis: colobomatous microphthalmia is a subset of this entity.

Distinguishing Features

Demonstrable coloboma of iris, retina, choroid or optic disc.
Mechanistically attributable to step 3 (optic fissure closure) rather than step 1 or 2.

Show evidence (1 reference)

PMID:30762128 SUPPORT Human Clinical

"optic fissure closure defect, it is referred to as colobomatous microphthalmia"

Defines the boundary between colobomatous and non-colobomatous microphthalmia.

CHARGE syndrome MONDO:0008965

Overlapping Features CHD7-related multisystem disorder in which ocular coloboma is a cardinal feature, accompanied by choanal atresia, cranial nerve dysfunction, characteristic ear anomalies and hearing loss, cardiac defects and growth retardation. Should be considered whenever coloboma co-occurs with any of these. Curated separately as `CHARGE_Syndrome`.

Distinguishing Features

Choanal atresia and characteristic external ear anomalies.
Cranial nerve dysfunction, especially anosmia and swallowing difficulty.
Pathogenic CHD7 variant.

Axenfeld-Rieger syndrome MONDO:0019187

Overlapping Features Anterior-segment dysgenesis with iris hypoplasia, corectopia, posterior embryotoxon and a high risk of glaucoma, caused chiefly by PITX2 or FOXC1 variants and often with dental and umbilical anomalies. Overlaps the complex-microphthalmia phenotype at the anterior segment, but the globe is usually of normal size. Curated separately as `Axenfeld-Rieger_syndrome`.

Distinguishing Features

Normal axial length with isolated anterior-segment dysgenesis.
Dental hypoplasia and redundant periumbilical skin.
PITX2 or FOXC1 variants.

Congenital cystic eye Not Yet Curated MONDO:0022825

Overlapping Features Complete failure of optic vesicle invagination leaving a cystic orbital mass with no recognisable globe. Clinically mimics anophthalmia, and a colobomatous cyst arising from an incompletely closed optic fissure can likewise dominate the orbit alongside a small globe. Orbital ultrasound or MRI distinguishes these and directs surgical planning.

Distinguishing Features

Cystic orbital mass on ultrasound or MRI.
Absence of any recognisable globe structure.

Fraser syndrome (cryptophthalmos) Not Yet Curated MONDO:0009046

Overlapping Features Failure of eyelid separation with skin running continuously over a malformed globe, most often as part of Fraser syndrome with cutaneous syndactyly and renal agenesis. Clinically resembles anophthalmia because no eye is visible, but the adnexa are abnormal rather than preserved — the key discriminator from clinical anophthalmia, whose definition explicitly requires intact adnexa.

Distinguishing Features

Absent palpebral fissure with skin continuous over the orbit.
Cutaneous syndactyly and renal agenesis.

Show evidence (1 reference)

PMID:20301552 SUPPORT Human Clinical

"Anophthalmia refers to complete absence of the globe in the presence of ocular adnexa (eyelids, conjunctiva, and lacrimal apparatus)."

The requirement for intact ocular adnexa in the definition of anophthalmia is what distinguishes it from cryptophthalmos.

Congenital rubella syndrome and other acquired destructive ocular disease Not Yet Curated MONDO:0017361

Overlapping Features A shrunken, disorganised globe following intrauterine infection, inflammation, trauma, retinopathy of prematurity or intraocular tumour can be mistaken for congenital microphthalmia. Congenital rubella is the classic infectious cause, producing cataract, retinopathy and microphthalmia together with deafness and cardiac defects; congenital Zika virus infection produced microphthalmia in 2.7% of reviewed cases. Serology, laterality, corneal diameter relative to axial length, and imaging for calcification or scarring distinguish an acquired small eye from a developmental one.

Distinguishing Features

Positive maternal or infant serology for a TORCH pathogen.
Intraocular calcification, chorioretinal scarring or disorganisation on imaging.
Accompanying sensorineural deafness and cardiac defects in congenital rubella.

Show evidence (1 reference)

PMID:38350011 SUPPORT Human Clinical

"microphthalmia was reported in 13 cases (13/479, 2.7%)"

Documents a destructive congenital infection producing microphthalmia, the principal acquired mimic.

{ }

Source YAML

click to show

name: Isolated Anophthalmia-Microphthalmia Syndrome
creation_date: "2026-08-01T07:00:00Z"
description: >-
  Isolated anophthalmia-microphthalmia syndrome is the non-syndromic pole of the
  microphthalmia-anophthalmia-coloboma (MAC) spectrum: a severe congenital
  developmental eye malformation in which the globe is absent (anophthalmia) or
  abnormally small (microphthalmia). Mechanistically it is best understood as
  failure at one of three sequential steps of early ocular morphogenesis —
  lateral evagination of the eye field into paired optic vesicles (4th week),
  invagination of the distal optic vesicle to form the bilayered optic cup, and
  fusion of the nasal and temporal edges of the optic fissure (7th week). Which
  step fails largely determines the resulting phenotype: the earliest and most
  complete failures abort globe formation and produce anophthalmia, partial
  failures of invagination and growth produce microphthalmia, and failure of the
  last step produces coloboma. The disorder is highly genetically heterogeneous;
  SOX2 (10-15% of all A/M) and OTX2 are the commonest single-gene causes, with
  the eye-field and lens transcription factors RAX, VSX2, PAX6, FOXE3 and
  MAB21L2, the BMP-family ligands GDF3 and GDF6, the posterior-microphthalmia
  genes MFRP and PRSS56, and the retinoic-acid-pathway genes ALDH1A3, STRA6,
  RBP4 and RARB also implicated, alongside copy-number and regulatory variants. Non-genetic first-trimester insults — gestational
  infection, maternal vitamin A deficiency, and teratogens such as thalidomide
  and retinoids — contribute a minority of cases.
category: Mendelian
parents:
- hereditary disease
- developmental eye disorder
synonyms:
- MAC spectrum
- microphthalmia-anophthalmia-coloboma spectrum
- nonsyndromic anophthalmia-microphthalmia syndrome
- isolated anophthalmia - microphthalmia
- clinical anophthalmia
- isolated pure microphthalmia
- A/M
disease_term:
  preferred_term: isolated anophthalmia-microphthalmia syndrome
  term:
    id: MONDO:0016764
    label: isolated anophthalmia-microphthalmia syndrome
notes: >-
  SCOPE AND BOUNDARIES. This entry curates MONDO:0016764, the umbrella
  "isolated" anophthalmia-microphthalmia (A/M) grouping term, and is organised
  around the three-step developmental-failure spine (evagination -> invagination
  -> optic fissure closure) that unifies the MAC spectrum. Its immediate MONDO
  child MONDO:0000170 (microphthalmia, isolated, with coloboma) is already
  curated separately as `Microphthalmia_with_Coloboma`; that entry is the
  detailed treatment of the optic-fissure-closure arm and its gene-level
  subtypes. To avoid duplication the coloboma arm is modelled here only as the
  third step of the developmental spine and as a subtype pointer, with the
  gene-by-gene coloboma detail left to that entry. Syndromic forms in which A/M
  is one feature of a defined multisystem disorder are curated as their own
  entries (STRA6-related syndromic microphthalmia / Matthew-Wood,
  RARB-related syndromic microphthalmia / MCOPS12, CHARGE syndrome,
  Axenfeld-Rieger syndrome, Bosma arhinia microphthalmia syndrome) and appear
  here only as differential diagnoses.

  THE "ISOLATED" LABEL IS AN ASCERTAINMENT QUALIFIER, NOT A BIOLOGICAL CLAIM.
  This is the single most important caveat for this entity and is curated
  explicitly rather than left implicit in the MONDO label. The two commonest
  causal genes both routinely produce extraocular disease: SOX2 loss classically
  causes psychomotor delay, brain malformation, hypogonadism and pituitary
  involvement, genital and renal anomalies and (in the AEG/MCOPS3 form,
  OMIM:206900) oesophageal atresia, and SOX2 variants have been reported in
  individuals with structurally normal eyes; OTX2 (MCOPS5) causes a combined
  pituitary-plus-eye phenotype. OMIM in fact assigns SOX2, OTX2, BMP4 and STRA6
  to the *syndromic* MCOPS series, not to the isolated MCOP/MCOPCB series,
  precisely because their phenotypes extend beyond the eye. Population data
  agree: extra-ocular abnormalities were present in 32.1% of Danish MO/AO cases
  (PMID:27552085) and only 16/35 children in a Swedish A/M cohort had genuinely
  isolated disease (PMID:35105264). "Isolated" here therefore means "no
  extraocular findings recognised at the time of ascertainment", and every
  apparently isolated case with a SOX2, OTX2, RAX or ALDH1A3 diagnosis warrants
  systemic — especially endocrine, neurological and gastrointestinal —
  evaluation.

  NUMBERED SUBTYPE SERIES. The MCOP (isolated microphthalmia) and MCOPCB
  (microphthalmia, isolated, with coloboma) gene-to-locus assignments below were
  re-derived independently from MONDO via OAK (definition text, OMIM xrefs and
  RO:0004003 gene relations); they were not taken from any deep-research output.
  Loci for which MONDO records no causal gene (MCOP1, MCOPCB1/2/4/6/8) are
  represented as such rather than being assigned a gene speculatively. Note that
  the MCOPS (syndromic microphthalmia) numbered series is a *different* series
  that sits under MONDO:0016073 (syndromic microphthalmia) and is therefore out
  of scope for this isolated-disease entry.
references:
- reference: PMID:20301552
  title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
  tags:
  - GeneReviews
has_subtypes:
- name: Anophthalmia
  display_name: Anophthalmia (clinical and true)
  description: >-
    Complete absence of the globe in the presence of ocular adnexa (eyelids,
    conjunctiva, lacrimal apparatus). "Clinical anophthalmia" denotes absence of
    any visible ocular structure although a histologically detectable remnant
    may persist; "true" anophthalmia denotes total absence of any ocular tissue.
    The boundary with extreme microphthalmia is a fine one. Represents failure at
    the earliest step (optic vesicle evagination/induction) and is the phenotype
    most strongly enriched for a molecular diagnosis.
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anophthalmia refers to complete absence of the globe in the presence of ocular adnexa"
    explanation: GeneReviews definition of anophthalmia within the MAC spectrum.
- name: Simple microphthalmia
  display_name: Simple (non-colobomatous) microphthalmia
  description: >-
    A globe of reduced size (total axial length at least 2 SD below the
    age-adjusted mean; <21 mm in adults, <14 mm in newborns) that is otherwise
    anatomically intact. Reflects a quantitative failure of optic-cup growth
    rather than a discrete structural closure defect.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Simple microphthalmia refers to an anatomically intact eye with a reduced axial length, without"
    explanation: Establishes the simple-versus-complex microphthalmia classification used for this subtype.
- name: Complex microphthalmia
  display_name: Complex microphthalmia (with segment anomalies)
  description: >-
    Microphthalmia accompanied by anterior-segment abnormalities
    (Axenfeld-Rieger anomaly, Peters anomaly, sclerocornea, cataract) or
    posterior-segment abnormalities (persistent primitive vitreous, chorioretinal
    coloboma, retinal dysplasia). Implies additional failure of anterior-segment
    or retinal differentiation on top of reduced globe growth.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "sclerocornea and cataract) or of the posterior segment (persistence of primitive vitreous, chorioretinal"
    explanation: Enumerates the segment anomalies that define complex microphthalmia.
- name: Colobomatous microphthalmia
  display_name: Colobomatous microphthalmia
  subtype_term:
    preferred_term: microphthalmia, isolated, with coloboma
    term:
      id: MONDO:0000170
      label: microphthalmia, isolated, with coloboma
  description: >-
    Microphthalmia combined with an optic fissure closure defect. This is the
    third-step (fissure-closure) arm of the spectrum and corresponds to MONDO
    child term MONDO:0000170; it is curated in detail in the separate
    `Microphthalmia_with_Coloboma` dismech entry and is represented here only as
    a spectrum pointer.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "optic fissure closure defect, it is referred to as colobomatous microphthalmia"
    explanation: Defines colobomatous microphthalmia as microphthalmia plus a fissure-closure defect.
- name: Posterior microphthalmia
  display_name: Posterior microphthalmia / nanophthalmia
  subtype_term:
    preferred_term: nanophthalmia
    term:
      id: MONDO:0005514
      label: nanophthalmia
  description: >-
    Reduced total axial length with normal anterior-segment dimensions
    (posterior microphthalmia), or the related nanophthalmia phenotype of extreme
    hyperopia, microcornea and frequent angle-closure glaucoma. Genetically
    distinct from severe A/M, being associated with MFRP (MCOP5) and PRSS56
    (MCOP6).
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nanophthalmia is a particular form of reduced eye size characterized by extreme hyperopia,"
    explanation: Distinguishes nanophthalmia and posterior microphthalmia from severe anophthalmia-microphthalmia.
- name: MCOP1
  display_name: Isolated microphthalmia 1 (OMIM:251600)
  subtype_term:
    preferred_term: isolated microphthalmia 1
    term:
      id: MONDO:0009631
      label: isolated microphthalmia 1
  description: >-
    Numbered isolated-microphthalmia locus mapped to chromosomal region 14q32.
    MONDO records no causal gene for this locus; verified via OAK, so no gene is
    asserted here.
- name: MCOP2
  display_name: Isolated microphthalmia 2 — VSX2 (OMIM:610093)
  subtype_term:
    preferred_term: isolated microphthalmia 2
    term:
      id: MONDO:0012409
      label: isolated microphthalmia 2
  description: >-
    Autosomal recessive isolated microphthalmia caused by biallelic VSX2 (CHX10)
    variants; gene assignment verified from the MONDO disease_series_by_gene
    definition.
  genes:
  - preferred_term: VSX2
    term:
      id: hgnc:1975
      label: VSX2
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "VSX2 is expressed during optic vesicle formation, and its"
    explanation: Places VSX2 in optic-vesicle-stage eye development, the mechanism underlying this recessive locus.
- name: MCOP3
  display_name: Isolated microphthalmia 3 — RAX (OMIM:611038)
  subtype_term:
    preferred_term: isolated microphthalmia 3
    term:
      id: MONDO:0012604
      label: isolated microphthalmia 3
  description: >-
    Autosomal recessive isolated microphthalmia/anophthalmia caused by biallelic
    RAX variants; gene assignment verified from MONDO.
  genes:
  - preferred_term: RAX
    term:
      id: hgnc:18662
      label: RAX
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biallelic mutations have been identified in 7 families with a bilateral and severe ocular A/M phenotype"
    explanation: Documents biallelic RAX variants in bilateral severe A/M families, the MCOP3 phenotype.
- name: MCOP4
  display_name: Isolated microphthalmia 4 — GDF6 (OMIM:613094)
  subtype_term:
    preferred_term: isolated microphthalmia 4
    term:
      id: MONDO:0013130
      label: isolated microphthalmia 4
  description: >-
    Isolated microphthalmia associated with GDF6, a BMP-family ligand; gene
    assignment verified from MONDO.
  genes:
  - preferred_term: GDF6
    term:
      id: hgnc:4221
      label: GDF6
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Variants in these genes account for 1.7% and 1% of A/M and coloboma patients screened for GDF3 or GDF6 mutations, respectively"
    explanation: Quantifies the GDF6 contribution to A/M and coloboma.
- name: MCOP5
  display_name: Isolated microphthalmia 5 — MFRP (OMIM:611040)
  subtype_term:
    preferred_term: isolated microphthalmia 5
    term:
      id: MONDO:0012605
      label: isolated microphthalmia 5
  description: >-
    Posterior microphthalmia/nanophthalmos with retinitis pigmentosa,
    foveoschisis and optic disc drusen, caused by MFRP variants; gene assignment
    verified from the MONDO RO:0004003 relation to HGNC:18121.
  genes:
  - preferred_term: MFRP
    term:
      id: hgnc:18121
      label: MFRP
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, biallelic mutations in MFRP were first associated with nanophthalmia (Sundin et al. 2005)."
    explanation: Documents biallelic MFRP variants causing nanophthalmia and posterior microphthalmia.
- name: MCOP6
  display_name: Isolated microphthalmia 6 — PRSS56 (OMIM:613517)
  subtype_term:
    preferred_term: isolated microphthalmia 6
    term:
      id: MONDO:0013293
      label: isolated microphthalmia 6
  description: >-
    Posterior microphthalmos and nanophthalmos caused by PRSS56 variants; gene
    assignment verified from MONDO.
  genes:
  - preferred_term: PRSS56
    term:
      id: hgnc:39433
      label: PRSS56
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "cause autosomal recessive posterior microphthalmia and nanophthalmia in"
    explanation: Documents biallelic PRSS56 variants causing recessive posterior microphthalmia and nanophthalmia.
- name: MCOP7
  display_name: Isolated microphthalmia 7 — GDF3 (OMIM:613704)
  subtype_term:
    preferred_term: isolated microphthalmia 7
    term:
      id: MONDO:0013377
      label: isolated microphthalmia 7
  description: >-
    Isolated microphthalmia caused by GDF3 variants, reported with ocular and
    skeletal anomalies; gene assignment verified from MONDO.
  genes:
  - preferred_term: GDF3
    term:
      id: hgnc:4218
      label: GDF3
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All of the pathogenic variants reported to date for GDF3 and GDF6 are heterozygous missense changes"
    explanation: Documents the heterozygous missense GDF3 variants underlying this locus.
- name: MCOP8
  display_name: Isolated microphthalmia 8 — ALDH1A3 (OMIM:615113)
  subtype_term:
    preferred_term: isolated microphthalmia 8
    term:
      id: MONDO:0014050
      label: isolated microphthalmia 8
  description: >-
    Autosomal recessive anophthalmia/microphthalmia caused by biallelic ALDH1A3
    variants that impair retinaldehyde dehydrogenase-mediated retinoic acid
    synthesis; gene assignment verified from MONDO.
  genes:
  - preferred_term: ALDH1A3
    term:
      id: hgnc:409
      label: ALDH1A3
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in ALDH1A3 are a frequent cause of A/M"
    explanation: Documents ALDH1A3 as a frequent cause of A/M in consanguineous pedigrees.
- name: MCOPCB series
  display_name: Numbered microphthalmia-with-coloboma loci (MCOPCB1-13)
  description: >-
    The parallel numbered series for microphthalmia with coloboma, all MONDO
    children of MONDO:0000170. Gene assignments re-derived from MONDO: MCOPCB3
    VSX2, MCOPCB5 SHH, MCOPCB7 ABCB6, MCOPCB9 TENM3, MCOPCB10 RBP4, MCOP/CB11
    FZD5, MCOP/CB13 NHEJ1. MONDO has no MCOPCB12 term at all, and records no
    causal gene for MCOPCB1 (X-linked),
    MCOPCB2, MCOPCB4, MCOPCB6 (digenic) or MCOPCB8. Detailed curation of this
    arm lives in the `Microphthalmia_with_Coloboma` entry.
inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    The dominant arm is driven by haploinsufficiency of dosage-sensitive
    developmental transcription factors, chiefly SOX2 and OTX2. The great
    majority of SOX2 variants arise de novo, but germline mosaicism is documented
    and must be factored into recurrence-risk counselling. OTX2 disease shows
    marked non-penetrance and variable expressivity even within a single family.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SOX2-related anophthalmia syndrome is transmitted in an autosomal dominant"
    explanation: States the dominant transmission of the commonest A/M gene.
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic variants in RAX, VSX2, ALDH1A3, FOXE3, MFRP and PRSS56 cause
    recessive disease, typically bilateral and severe, and are enriched in
    consanguineous pedigrees although compound heterozygosity occurs in
    non-consanguineous families. Heterozygous carriers are usually unaffected.
  evidence:
  - reference: PMID:21976963
    reference_title: VSX2 mutations in autosomal recessive microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in VSX2 represent an important cause of autosomal recessive microphthalmia in consanguineous pedigrees."
    explanation: Documents the autosomal recessive arm of isolated microphthalmia.
- name: X-linked inheritance
  inheritance_term:
    preferred_term: X-linked inheritance
    term:
      id: HP:0001417
      label: X-linked inheritance
  description: >-
    An X-linked numbered locus exists in the isolated series (MCOPCB1,
    MONDO:0024549 / OMIM:300345), and X-linked genes such as BCOR contribute to
    the wider MAC spectrum. Deletions involving the X chromosome were among the
    causal findings in a prospective MAC cohort.
  evidence:
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "novel variants in six known MAC genes (SOX2, KMT2D, MAB21L2, ALDH1A3, BCOR and"
    explanation: Identifies the X-linked gene BCOR among causal findings in a real-world MAC cohort; the numbered X-linked locus MCOPCB1 itself is documented in MONDO/OMIM rather than in this paper, so this is scored PARTIAL.
prevalence:
- population: Denmark, live births 1995-2012
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 12.0
  notes: >-
    Registry-based Danish national cohort (1,174,299 live births). Birth
    prevalence of microphthalmia or anophthalmia (MO/AO) alone was 1.2 per 10,000
    live births, normalised here to 12 per 100,000. The wider MO/AO/coloboma
    birth prevalence in the same cohort was 3.6 per 10,000 (36 per 100,000).
  evidence:
  - reference: PMID:27552085
    reference_title: Congenital Microphthalmia, Anophthalmia and Coloboma among Live Births in Denmark.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the average birth prevalence of MO/AO/coloboma was 3.6/10,000 live births and of MO/AO was"
    explanation: Population-based Danish birth-prevalence estimate for microphthalmia and anophthalmia.
- population: Worldwide (pooled reviews and birth-defect surveillance)
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 20.0
  rate_low: 20.0
  rate_high: 30.0
  notes: >-
    Pooled estimates place the combined anophthalmia/microphthalmia birth
    prevalence at up to 2-3 per 10,000 live births (20-30 per 100,000). Estimates
    vary with surveillance system and with whether coloboma and syndromic cases
    are included.
  evidence:
  - reference: PMID:35716026
    reference_title: Exome sequencing identifies genetic variants in anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anophthalmia and microphthalmia (A/M) are rare birth defects affecting up to 2"
    explanation: Contemporary birth-prevalence figure for A/M from a US population-based study.
  - reference: PMID:18039390
    reference_title: Anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "of these conditions is up to 30 per 100,000 population"
    explanation: Upper-bound combined birth prevalence from the Orphanet review.
- population: Blind children worldwide (disease-burden fraction, not a population rate)
  measure_type: UNKNOWN
  prevalence_class: UNKNOWN
  notes: >-
    Not a population occurrence rate but a burden fraction, recorded here for
    context: microphthalmia is reported in up to 11% of blind children, and A/M
    accounts for roughly 3-12% of childhood visual impairment.
  evidence:
  - reference: PMID:37181112
    reference_title: Animal and cellular models of microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Up to 11% of blind children are reported to have microphthalmia, yet currently no"
    explanation: Quantifies the contribution of microphthalmia to childhood blindness.
pathophysiology:
- name: Eye Field Transcription Factor Network Dosage Loss
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    The proximal molecular lesion in most genetically explained cases is loss of
    functional dosage of a transcription factor that specifies and maintains the
    anterior neural-plate eye field. SOX2 and OTX2 act as dosage-sensitive hubs
    that bind regulatory elements of downstream eye-field genes including RAX and
    PAX6; heterozygous loss-of-function variants, whole-gene deletions and
    regulatory or copy-number lesions all reduce effective dosage. Biallelic loss
    of RAX, VSX2 or FOXE3 removes the corresponding node outright. Because these
    factors act sequentially and combinatorially, the developmental stage at
    which the network first fails, rather than the identity of the gene alone,
    sets the severity of the resulting malformation.
  biological_processes:
  - preferred_term: eye field specification
    term:
      id: GO:0060898
      label: eye field cell fate commitment involved in camera-type eye formation
    modifier: DECREASED
  - preferred_term: embryonic camera-type eye formation
    term:
      id: GO:0060900
      label: embryonic camera-type eye formation
    modifier: DECREASED
  locations:
  - preferred_term: optic vesicle
    term:
      id: UBERON:0004128
      label: optic vesicle
  genes:
  - preferred_term: SOX2
    term:
      id: hgnc:11195
      label: SOX2
  - preferred_term: OTX2
    term:
      id: hgnc:8522
      label: OTX2
  - preferred_term: PAX6
    term:
      id: hgnc:8620
      label: PAX6
  - preferred_term: MAB21L2
    term:
      id: hgnc:6758
      label: MAB21L2
  - preferred_term: FOXE3
    term:
      id: hgnc:3808
      label: FOXE3
  downstream:
  - target: Failure of Optic Vesicle Evagination
    description: Loss of eye-field specification prevents the eye-forming region from evaginating into paired optic vesicles.
  - target: Failure of Optic Cup Invagination and Growth
    description: Partial dosage loss permits vesicle formation but impairs subsequent invagination and growth.
  - target: Failure of Optic Fissure Closure
    description: Reduced dosage of the same network perturbs ventral optic-cup patterning required for fissure fusion.
  - target: Retinal Progenitor Specification Failure and RPE Fate Shift
    description: Loss of VSX2, itself a member of this eye-field network, removes the neural-retina specification and RPE-repression node.
  - target: Extraocular Pleiotropy of Eye Field Transcription Factors
    description: The same dosage lesion acts in the non-ocular expression domains of SOX2, OTX2 and RAX, producing extraocular disease.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This process of eye formation is directed by a network of genes, and any disruption of these"
    explanation: States that a gene network directs eye formation and that its disruption produces A/M and coloboma.
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "major gene responsible for A/M is SOX2, accounting for 10-15% of affected individuals, usually those"
    explanation: Identifies SOX2 dosage loss as the single commonest molecular lesion.
- name: Failure of Optic Vesicle Evagination
  biological_scale: TISSUE
  role: mediator
  description: >-
    STEP 1 OF THE THREE-STEP SPINE. During neurulation (4th week of human
    gestation) the eye-forming region of the anterior neural plate evaginates
    laterally, splitting the single eye field into right and left optic vesicles.
    Complete failure of this earliest morphogenetic step — through lack of
    induction at the primitive neural tube, failure of the optic pit to enlarge,
    or (in some models) secondary regression of an already-formed structure —
    aborts globe formation altogether. This is the step whose failure yields
    anophthalmia, and it explains why histologically detectable vestigial ocular
    tissue is variably found in anophthalmic sockets.
  biological_processes:
  - preferred_term: optic vesicle formation
    term:
      id: GO:0003403
      label: optic vesicle formation
    modifier: DECREASED
  - preferred_term: optic vesicle morphogenesis
    term:
      id: GO:0003404
      label: optic vesicle morphogenesis
    modifier: DECREASED
  cell_types:
  - preferred_term: retinal progenitor cell
    term:
      id: CL:0002672
      label: retinal progenitor cell
  locations:
  - preferred_term: optic vesicle
    term:
      id: UBERON:0004128
      label: optic vesicle
  genes:
  - preferred_term: RAX
    term:
      id: hgnc:18662
      label: RAX
  downstream:
  - target: Absent or Severely Reduced Globe Formation
    description: Failure of the earliest evagination step aborts globe formation, producing anophthalmia.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "eye-forming region evaginates laterally, splitting the eye field into right and left optic vesicles."
    explanation: Defines the evagination step whose failure is modelled by this node.
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "may result from a lack of induction at the level of the primitive neural tube or a failure of the optic pit"
    explanation: States the proposed mechanism by which failure at this earliest step produces anophthalmia.
- name: Failure of Optic Cup Invagination and Growth
  biological_scale: TISSUE
  role: mediator
  description: >-
    STEP 2 OF THE THREE-STEP SPINE. Extension of the optic vesicle drives
    invagination of its distal surface, partitioning it into proximal (optic
    stalk) and distal (optic cup) territories; the two layers of the cup become
    the neural retina and the retinal pigment epithelium, while the overlying
    surface ectoderm is induced to form the lens placode. Partial rather than
    complete failure at this step — impaired cell movements integral to
    invagination, failure of lens induction, or defective early retinal
    differentiation — yields a globe that forms but remains small. The
    BMP-family ligands GDF3 and GDF6 pattern this step, and heterozygous
    missense variants in either produce ocular anomalies ranging from bilateral
    anophthalmia to unilateral coloboma. This is the step whose failure yields
    microphthalmia rather than anophthalmia.
  biological_processes:
  - preferred_term: optic cup formation
    term:
      id: GO:0003408
      label: optic cup formation involved in camera-type eye development
    modifier: DECREASED
  - preferred_term: optic cup morphogenesis
    term:
      id: GO:0002072
      label: optic cup morphogenesis involved in camera-type eye development
    modifier: DECREASED
  - preferred_term: lens development
    term:
      id: GO:0002088
      label: lens development in camera-type eye
    modifier: DECREASED
  locations:
  - preferred_term: optic cup
    term:
      id: UBERON:0003072
      label: optic cup
  - preferred_term: lens placode
    term:
      id: UBERON:0003073
      label: lens placode
  genes:
  - preferred_term: GDF6
    term:
      id: hgnc:4221
      label: GDF6
  - preferred_term: GDF3
    term:
      id: hgnc:4218
      label: GDF3
  downstream:
  - target: Absent or Severely Reduced Globe Formation
    description: Impaired invagination and growth of the optic cup produce a small globe.
  - target: Increased Apoptosis and Reduced Proliferation in the Developing Optic Vesicle
    description: Disrupted optic-cup morphogenesis is executed cellularly as excess apoptosis with reduced progenitor proliferation.
  - target: Anterior and Posterior Segment Dysgenesis
    description: Failure of lens induction and early retinal differentiation produces associated segment anomalies.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The two layers of the optic cup form the neural and pigmented retina."
    explanation: Defines the invagination step and the tissues it generates.
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "anophthalmia can occur following failure of lens induction (Inoue et al. 2007), early retinal"
    explanation: Identifies lens-induction and early-retinal-differentiation failure at this step as mechanisms of A/M.
- name: Failure of Optic Fissure Closure
  biological_scale: TISSUE
  role: mediator
  description: >-
    STEP 3 OF THE THREE-STEP SPINE. Invagination of the optic cup is asymmetric,
    leaving a ventral furrow — the optic fissure — running from the cup into the
    optic stalk, through which the hyaloid artery enters. The nasal and temporal
    edges of this fissure must fuse during the 7th week of human development.
    Failure of this epithelial fusion produces coloboma, which may involve iris,
    retina, choroid and optic nerve; when it co-occurs with a small globe the
    result is colobomatous microphthalmia. Retinoic acid receptor signalling
    regulates fissure closure through independent actions on the ventral optic
    cup and on the neural-crest-derived periocular mesenchyme. NOTE: the
    gene-level detail of this arm is curated in the separate
    `Microphthalmia_with_Coloboma` entry (MONDO:0000170).
  biological_processes:
  - preferred_term: closure of optic fissure
    term:
      id: GO:0061386
      label: closure of optic fissure
    modifier: DECREASED
  cell_types:
  - preferred_term: periocular mesenchymal cell (neural crest derived)
    term:
      id: CL:0000333
      label: migratory neural crest cell
  locations:
  - preferred_term: optic fissure
    term:
      id: UBERON:0005412
      label: optic fissure
  downstream:
  - target: Coloboma
    description: Failure of nasal-temporal fissure fusion leaves a persistent ventral tissue defect.
  - target: Anterior and Posterior Segment Dysgenesis
    description: A persistent fissure defect disrupts normal iris, retinal, choroidal and optic-nerve architecture.
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the ocular malformations that result from failure of closure of the optic"
    explanation: GeneReviews states that coloboma results from failure of closure of the optic fissure.
  - reference: PMID:21555593
    reference_title: Retinoic acid receptor signaling regulates choroid fissure closure through independent mechanisms in the ventral optic cup and periocular mesenchyme.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "RAR signaling regulates choroid fissure closure in zebrafish by acting on both the ventral optic cup and the POM"
    explanation: Zebrafish evidence that retinoic acid receptor signalling controls fissure closure via two independent tissue compartments.
- name: Retinoic Acid Signalling Deficiency
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    A coherent sub-pathway converging on the same morphogenetic steps. Vitamin A
    (retinol) is delivered to the embryo bound to RBP4 and taken up by the
    membrane receptor STRA6; ALDH1A3 (retinaldehyde dehydrogenase 3) oxidises
    retinaldehyde to all-trans retinoic acid; RARB transduces the signal in the
    nucleus. Loss of any step depletes retinoic acid in the ventral optic cup and
    periocular mesenchyme, impairing optic-cup morphogenesis and fissure closure.
    Biallelic ALDH1A3 variants account for approximately 11% of recessively
    inherited severe developmental eye anomalies. This node is also the point of
    convergence for the non-genetic retinoid causes (maternal vitamin A
    deficiency, exogenous retinoid teratogens), which perturb the same pathway
    from the opposite direction — both loss and gain of retinoic acid signalling
    cause structural eye defects.
  biological_processes:
  - preferred_term: retinoic acid biosynthetic process
    term:
      id: GO:0002138
      label: retinoic acid biosynthetic process
    modifier: DECREASED
  chemical_entities:
  - preferred_term: all-trans-retinoic acid
    term:
      id: CHEBI:15367
      label: all-trans-retinoic acid
    modifier: DECREASED
  genes:
  - preferred_term: ALDH1A3
    term:
      id: hgnc:409
      label: ALDH1A3
  downstream:
  - target: Failure of Optic Cup Invagination and Growth
    description: Retinoic acid depletion impairs ventral optic-cup morphogenesis and growth.
  - target: Failure of Optic Fissure Closure
    description: Retinoic acid receptor signalling is required in both the ventral optic cup and the periocular mesenchyme for fissure closure.
  evidence:
  - reference: PMID:36997679
    reference_title: Clinical and genetic analysis further delineates the phenotypic spectrum of ALDH1A3-related anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biallelic pathogenic variants in ALDH1A3 are responsible for approximately 11%"
    explanation: Quantifies the contribution of the retinoic-acid-synthesis arm to recessive severe eye anomalies.
  - reference: PMID:21555593
    reference_title: Retinoic acid receptor signaling regulates choroid fissure closure through independent mechanisms in the ventral optic cup and periocular mesenchyme.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Retinoic acid receptor (RAR) signaling is required for morphogenesis of the ventral optic cup and closure of the choroid fissure"
    explanation: Establishes the requirement for retinoic acid receptor signalling in the two morphogenetic steps this node feeds.
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "STRA6, RARB, ALDH1A3 and RBP4. Both loss and gain of retinoic acid signaling cause structural defects"
    explanation: Names the four retinoid-pathway genes and states the bidirectional dose sensitivity of the pathway.
- name: Retinal Progenitor Specification Failure and RPE Fate Shift
  biological_scale: CELLULAR
  role: mediator
  description: >-
    VSX2 (CHX10) is expressed from optic-vesicle stage in the presumptive neural
    retina, where it drives retinal-progenitor proliferation and represses the
    retinal-pigment-epithelium programme. Biallelic VSX2 loss shifts the
    neural-retina/RPE boundary toward RPE identity and depletes the progenitor
    pool that would otherwise expand the optic cup, producing bilateral
    microphthalmia. The mutations reported in recessive microphthalmia disrupt
    either the homeodomain or the conserved CVC motif required for DNA binding
    and repression.
  cell_types:
  - preferred_term: retinal progenitor cell
    term:
      id: CL:0002672
      label: retinal progenitor cell
  - preferred_term: retinal pigment epithelial cell
    term:
      id: CL:0002586
      label: retinal pigment epithelial cell
  biological_processes:
  - preferred_term: neural retina development
    term:
      id: GO:0003407
      label: neural retina development
    modifier: DECREASED
  - preferred_term: retinal pigment epithelium development
    term:
      id: GO:0003406
      label: retinal pigment epithelium development
    modifier: INCREASED
  genes:
  - preferred_term: VSX2
    term:
      id: hgnc:1975
      label: VSX2
  downstream:
  - target: Failure of Optic Cup Invagination and Growth
    description: Loss of the retinal progenitor pool prevents the optic cup from expanding to normal size.
  evidence:
  - reference: PMID:21976963
    reference_title: VSX2 mutations in autosomal recessive microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This p.G223A mutation affects the conserved CVC motif that was shown to be important for DNA binding and repression activities of VSX2."
    explanation: Links the human recessive microphthalmia mutations to loss of VSX2 DNA-binding and repressive function.
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "VSX2 is expressed during optic vesicle formation, and its"
    explanation: Places VSX2 action at the optic-vesicle stage of the developmental spine.
  - reference: PMID:25927996
    reference_title: Genetic chimeras reveal the autonomy requirements for Vsx2 in embryonic retinal progenitor cells.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We show that Vsx2 maintains retinal identity in part through the cell-autonomous repression of the retinal pigment epithelium determinant Mitf"
    explanation: Mouse-chimera evidence that Vsx2 maintains neural-retina identity by cell-autonomously repressing the RPE determinant MITF, the fate shift modelled by this node.
- name: Increased Apoptosis and Reduced Proliferation in the Developing Optic Vesicle
  biological_scale: CELLULAR
  role: amplifier
  description: >-
    A convergent cellular execution mechanism identified in patient-derived
    induced-pluripotent-stem-cell optic vesicles from unrelated microphthalmia
    patients: optic-vesicle diameter is significantly reduced from day 20, with
    upregulation of apoptosis-initiating and extracellular-matrix genes,
    increased apoptosis and decreased proliferation. Caspase-8 inhibition reduced
    apoptosis in one patient model, identifying a shared and potentially
    tractable downstream node distinct from the specific upstream genetic lesion.
  cell_types:
  - preferred_term: retinal progenitor cell
    term:
      id: CL:0002672
      label: retinal progenitor cell
  biological_processes:
  - preferred_term: apoptotic process
    term:
      id: GO:0006915
      label: apoptotic process
    modifier: INCREASED
  - preferred_term: cell population proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: DECREASED
  downstream:
  - target: Absent or Severely Reduced Globe Formation
    description: Excess apoptosis with reduced proliferation depletes the cell mass available to build a normal-sized globe.
  evidence:
  - reference: PMID:38821055
    reference_title: Disruption of common ocular developmental pathways in patient-derived optic vesicle models of microphthalmia.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Increased apoptosis was observed in microphthalmia OVs with reduced phospho-histone 3 (pH3+) cells confirming decreased cell proliferation at day 35."
    explanation: Patient-derived iPSC optic vesicles demonstrate the apoptosis and proliferation imbalance modelled by this node.
  - reference: PMID:38821055
    reference_title: Disruption of common ocular developmental pathways in patient-derived optic vesicle models of microphthalmia.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These data reveal shared pathophysiological mechanisms contributing to a microphthalmia phenotype."
    explanation: Supports treating this cellular imbalance as a convergent mechanism across genetically distinct microphthalmia.
- name: Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis
  biological_scale: ORGANISM
  role: trigger
  description: >-
    A minority of A/M is non-genetic. The same three morphogenetic steps are
    vulnerable to first-trimester environmental insult: gestationally acquired
    infection (the strongest environmental evidence), maternal vitamin A
    deficiency, exposure to X-rays, solvent misuse, and thalidomide. Exogenous
    retinoids act on the same retinoic-acid node as the STRA6/ALDH1A3/RARB
    genetic lesions. Because the critical window is embryonic there is no
    postnatal trigger, and the malformation itself is not transmissible.
  downstream:
  - target: Failure of Optic Cup Invagination and Growth
    description: First-trimester teratogenic or infectious insult perturbs optic-cup morphogenesis during the critical window.
  - target: Retinoic Acid Signalling Deficiency
    description: Maternal vitamin A deficiency and retinoid teratogens perturb embryonic retinoic acid availability directly.
  evidence:
  - reference: PMID:18039390
    reference_title: Anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The strongest evidence appears to be with gestational-acquired infections, but may"
    explanation: Ranks gestational infection first among the recognised environmental causes of A/M.
- name: Absent or Severely Reduced Globe Formation
  biological_scale: TISSUE
  role: central_effector
  description: >-
    The convergent structural outcome of all upstream routes: a globe that is
    absent, or whose total axial length is at least two standard deviations below
    the age-adjusted mean (<21 mm in adults, <14 mm in newborns). Severe
    microphthalmia is defined by a corneal diameter under 4 mm with total axial
    length under 10 mm at birth or under 12 mm after one year. The structural
    deficit is permanent and does not remit; asymmetric and unilateral
    involvement is common, implying differences in developmental robustness and
    buffering between the two sides. A mechanistically separate route to a small
    globe is restricted axial growth with a normal anterior segment (posterior
    microphthalmia and nanophthalmia), caused by biallelic MFRP or PRSS56
    variants.
  locations:
  - preferred_term: eyeball of camera-type eye
    term:
      id: UBERON:0010230
      label: eyeball of camera-type eye
  biological_processes:
  - preferred_term: camera-type eye development
    term:
      id: GO:0043010
      label: camera-type eye development
    modifier: DECREASED
  genes:
  - preferred_term: MFRP
    term:
      id: hgnc:18121
      label: MFRP
  - preferred_term: PRSS56
    term:
      id: hgnc:39433
      label: PRSS56
  downstream:
  - target: Anophthalmia
    description: Complete failure of globe formation presents clinically as anophthalmia.
  - target: Microphthalmia
    description: Partial failure of globe growth presents clinically as microphthalmia.
  - target: Microcornea
    description: Reduced globe size is accompanied by a reduced corneal diameter.
  - target: Failure of Orbital and Periocular Growth
    description: The absent or small globe fails to provide the mechanical stimulus that drives orbital expansion.
  - target: Congenital Visual Deprivation
    description: Absent or malformed ocular tissue prevents formation of a functional visual pathway.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "deviations (SD) below the age-adjusted population mean; < 21 mm in adults and < 14 mm in newborns"
    explanation: Provides the quantitative structural definition of the convergent outcome node.
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Asymmetric involvement is common, suggesting differences in robustness and buffering mechanisms between the two sides."
    explanation: Notes the asymmetry of involvement characteristic of this convergent outcome.
- name: Failure of Orbital and Periocular Growth
  biological_scale: TISSUE
  role: consequence
  description: >-
    Postnatal expansion of the bony orbit, conjunctival cul-de-sac and palpebral
    fissure is driven mechanically by growth of the globe. When the globe is
    absent or very small this stimulus is lost, and the orbit, eyelids and
    midface on the affected side remain hypoplastic, producing progressive facial
    asymmetry. This is the rationale for the principal therapeutic intervention
    in this disorder — serial conformer-assisted socket expansion begun in
    infancy, which in a case series increased mean lid length by 90.9% in
    anophthalmia and 31.3% in microphthalmia.
  locations:
  - preferred_term: orbit of skull
    term:
      id: UBERON:0001697
      label: orbit of skull
  downstream:
  - target: Orbital and Palpebral Fissure Hypoplasia
    description: Loss of the globe-derived growth stimulus leaves the orbit and palpebral fissure underdeveloped.
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an ocularist can start shortly after birth to expand the palpebral fissures"
    explanation: GeneReviews implies globe-dependent orbital growth by describing the need for mechanical expansion when the globe is absent; the causal dependency itself is not stated explicitly, so this is scored PARTIAL.
  - reference: PMID:36257503
    reference_title: Socket expansion with conformers in congenital anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Percentage increases in lid length were 90.9%, 61.2%, and 31.3% in anophthalmia, clinical anophthalmia, and microphthalmia, respectively"
    explanation: The conformer series quantifies the growth deficit that mechanical expansion corrects.
- name: Anterior and Posterior Segment Dysgenesis
  biological_scale: TISSUE
  role: consequence
  description: >-
    In complex microphthalmia the same morphogenetic failures that reduce globe
    size also disrupt differentiation of individual ocular structures, producing
    anterior-segment anomalies (Axenfeld-Rieger anomaly, Peters anomaly,
    sclerocornea, cataract) and posterior-segment anomalies (persistent primitive
    vitreous, chorioretinal coloboma, retinal dysplasia). In a prospective MAC
    cohort 44% had complex ocular features beyond the MAC phenotype itself.
  locations:
  - preferred_term: eyeball of camera-type eye
    term:
      id: UBERON:0010230
      label: eyeball of camera-type eye
  downstream:
  - target: Cataract
    description: Disrupted lens induction and differentiation produces congenital lens opacity.
  - target: Sclerocornea
    description: Failure of anterior-segment differentiation produces an opaque, sclera-like cornea.
  - target: Glaucoma
    description: Anterior-segment dysgenesis obstructs aqueous outflow and raises intraocular pressure.
  - target: Retinal detachment
    description: Dysplastic retina and abnormal vitreous predispose to later retinal detachment.
  evidence:
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "from 44 unrelated families found 44% had additional ocular features (complex)"
    explanation: Quantifies the frequency of additional complex ocular features in a prospective MAC cohort.
- name: Extraocular Pleiotropy of Eye Field Transcription Factors
  biological_scale: ORGANISM
  role: consequence
  description: >-
    THE HONESTY NODE FOR THE "ISOLATED" LABEL. SOX2, OTX2 and RAX are not
    eye-restricted. SOX2 is required for pluripotency and multiple early
    developmental programmes; OTX2 is expressed in the posterior pituitary,
    retina, ear, thalamus and choroid plexus during human embryogenesis; RAX
    patterns the ventral forebrain and hypothalamus. Consequently the same
    dosage lesion that produces A/M frequently produces psychomotor delay,
    ventriculomegaly and corpus-callosum hypoplasia, hypogonadism and pituitary
    dysfunction, growth and renal anomalies, and — in the AEG/MCOPS3 form —
    oesophageal atresia. SOX2 variants have been reported in individuals with
    structurally normal eyes, and truncating RAX variants have caused
    anophthalmia with hypopituitarism, diabetes insipidus and cleft palate. A
    disorder labelled "isolated" is therefore isolated only until it is looked
    for elsewhere.
  downstream:
  - target: Global developmental delay
    description: Extraocular action of the same transcription factors impairs neurodevelopment.
  - target: Hypopituitarism
    description: OTX2 and RAX act in pituitary and hypothalamic development.
  - target: Hypogonadism
    description: Pituitary and gonadal-axis involvement follows from the same dosage lesion.
  - target: Esophageal atresia
    description: SOX2 loss disrupts foregut separation, the AEG/MCOPS3 association.
  - target: Hypoplasia of the corpus callosum
    description: SOX2 loss produces midline forebrain malformation.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common extraocular features are psychomotor"
    explanation: Introduces the canonical extraocular feature list for SOX2-related A/M.
  - reference: PMID:33950863
    reference_title: The phenotypic spectrum associated with OTX2 mutations in humans.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary."
    explanation: Demonstrates the non-ocular expression domains that underlie OTX2 extraocular disease.
  - reference: PMID:37163579
    reference_title: "SOX2 pathogenic variants with normal eyes: Expanding the phenotypic spectrum."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our patients provide further evidence for broadening the phenotypic spectrum of SOX2 mutations and"
    explanation: Direct evidence that the SOX2 phenotype is not confined to the eye, undermining a strictly ocular reading of the isolated label.
- name: Congenital Visual Deprivation
  biological_scale: ORGANISM
  role: outcome
  description: >-
    Absence or severe malformation of the globe prevents formation of a normal
    retinal image and, in bilateral disease, of a functional visual pathway.
    Visual outcome depends principally on laterality, residual retinal and
    optic-nerve development and the status of the fellow eye. Bilateral severe
    disease produces lifelong blindness; unilateral disease may preserve useful
    vision but leaves the fellow eye at risk from amblyopia and injury. In a
    paediatric A/M cohort 10 of 35 children were totally blind or had light
    perception only.
  downstream:
  - target: Visual impairment
    description: Loss of ocular tissue directly reduces visual function.
  - target: Blindness
    description: Bilateral severe disease abolishes form vision.
  - target: Amblyopia
    description: In unilateral disease the fellow eye is at risk of deprivation and refractive amblyopia.
  evidence:
  - reference: PMID:35105264
    reference_title: "Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ten cases were totally blind or had light perception."
    explanation: Quantifies the visual outcome of the convergent structural deficit.
phenotypes:
- category: Ocular
  name: Anophthalmia
  description: >-
    Complete absence of the globe within an orbit that retains its adnexa. The
    defining severe pole of the spectrum, produced by failure at the earliest
    (evagination) developmental step.
  phenotype_term:
    preferred_term: Anophthalmia
    term:
      id: HP:0000528
      label: Anophthalmia
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anophthalmia refers to complete absence of the globe in the presence of ocular adnexa"
    explanation: GeneReviews clinical definition of the defining phenotype.
- category: Ocular
  name: Microphthalmia
  description: >-
    A structurally small globe, defined as a total axial length at least two
    standard deviations below the age-adjusted mean (<21 mm in adults, <14 mm in
    newborns). May be unilateral or bilateral and is frequently asymmetric.
  phenotype_term:
    preferred_term: Microphthalmia
    term:
      id: HP:0000568
      label: Microphthalmia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Microphthalmia refers to a decreased size of the eye"
    explanation: Defines the phenotype and its quantitative threshold.
  - reference: PMID:36997679
    reference_title: Clinical and genetic analysis further delineates the phenotypic spectrum of ALDH1A3-related anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All affected individuals had bilateral anophthalmia/microphthalmia (A/M)"
    explanation: Supports the VERY_FREQUENT band — A/M was present in every affected individual across seven ALDH1A3 families.
- category: Ocular
  name: Coloboma
  description: >-
    A defect of ocular tissue resulting from failure of optic fissure closure,
    which may affect iris, retina, choroid and optic nerve. Curated here as the
    third-step phenotype of the developmental spine; gene-level detail is in the
    separate `Microphthalmia_with_Coloboma` entry.
  phenotype_term:
    preferred_term: Coloboma
    term:
      id: HP:0000589
      label: Coloboma
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the ocular malformations that result from failure of closure of the optic"
    explanation: Directly ties the coloboma phenotype to the third developmental step.
- category: Ocular
  name: Microcornea
  description: >-
    Reduced corneal diameter accompanying the small globe. A corneal diameter
    below 4 mm together with a very short axial length defines severe
    microphthalmia.
  phenotype_term:
    preferred_term: Microcornea
    term:
      id: HP:0000482
      label: Microcornea
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Microphthalmia is classed as severe if the corneal diameter is < 4 mm"
    explanation: Establishes reduced corneal diameter as part of the severe microphthalmia phenotype.
- category: Ocular
  name: Cataract
  description: >-
    Congenital lens opacity, one of the anterior-segment anomalies that define
    complex microphthalmia. Reflects disrupted lens induction and differentiation
    at the optic-cup stage.
  phenotype_term:
    preferred_term: Cataract
    term:
      id: HP:0000518
      label: Cataract
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "sclerocornea and cataract) or of the posterior segment (persistence of primitive vitreous, chorioretinal"
    explanation: Lists cataract among the anterior-segment anomalies defining complex microphthalmia.
- category: Ocular
  name: Sclerocornea
  description: >-
    Opacification of the cornea with a sclera-like appearance, part of the
    anterior-segment dysgenesis seen in complex microphthalmia and characteristic
    of biallelic FOXE3 and some RAX presentations.
  phenotype_term:
    preferred_term: Sclerocornea
    term:
      id: HP:0000647
      label: Sclerocornea
  evidence:
  - reference: PMID:29136273
    reference_title: "FOXE3 mutations: genotype-phenotype correlations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "associated with recessively inherited primary aphakia, sclerocornea and microphthalmia."
    explanation: Documents the recessive FOXE3 phenotype of primary aphakia, sclerocornea and microphthalmia.
- category: Ocular
  name: Glaucoma
  description: >-
    Raised intraocular pressure with optic-nerve damage, arising from
    anterior-segment dysgenesis and crowded anterior-chamber anatomy in the small
    eye; particularly characteristic of the nanophthalmic end of the spectrum.
  phenotype_term:
    preferred_term: Glaucoma
    term:
      id: HP:0000501
      label: Glaucoma
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nanophthalmia is a particular form of reduced eye size characterized by extreme hyperopia, microcornea and frequently glaucoma."
    explanation: Documents glaucoma as a recurrent complication in the reduced-eye-size phenotype.
- category: Ocular
  name: Retinal detachment
  description: >-
    Separation of the neurosensory retina, a late complication of the dysplastic
    retina and abnormal vitreous in malformed eyes. Observed in 9% of a
    prospective MAC cohort, presenting from the first to the third decade.
  phenotype_term:
    preferred_term: Retinal detachment
    term:
      id: HP:0000541
      label: Retinal detachment
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "from 44 unrelated families found 44% had additional ocular features (complex)"
    explanation: The prospective cohort from which the 9% retinal-detachment figure derives; the abstract quantifies the complex-ocular-feature denominator rather than the detachment rate itself, so this is scored PARTIAL.
- category: Ocular
  name: Orbital and Palpebral Fissure Hypoplasia
  description: >-
    Underdevelopment of the bony orbit, conjunctival fornices and palpebral
    fissure on the affected side, a secondary consequence of the missing
    globe-derived mechanical growth stimulus. Mean initial lid length was 11.0 mm
    in anophthalmia versus 16.9 mm in microphthalmia in a conformer case series.
  phenotype_term:
    preferred_term: Blepharophimosis
    term:
      id: HP:0000581
      label: Blepharophimosis
  evidence:
  - reference: PMID:36257503
    reference_title: Socket expansion with conformers in congenital anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mean initial lid lengths in anophthalmia, clinical anophthalmia,"
    explanation: Quantifies the palpebral fissure shortening produced by absent globe growth.
- category: Ocular
  name: Visual impairment
  description: >-
    Reduced visual function, the principal functional consequence. Anophthalmia
    and microphthalmia account for approximately 3-12% of childhood visual
    impairment.
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  frequency: FREQUENT
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "frequently responsible for severe visual impairment, accounting for approximately 3% to 12% of visual"
    explanation: Documents severe visual impairment as the dominant functional outcome; the review's qualitative "frequently" maps to the FREQUENT band.
- category: Ocular
  name: Blindness
  description: >-
    Total loss of form vision, the outcome of bilateral severe disease. Ten of 35
    children in a Swedish A/M cohort were totally blind or had light perception
    only.
  phenotype_term:
    preferred_term: Blindness
    term:
      id: HP:0000618
      label: Blindness
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:35105264
    reference_title: "Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ten cases were totally blind or had light perception."
    explanation: Supports the OCCASIONAL band (10/35 = 29%, within the 5-29% range) in a paediatric A/M cohort.
- category: Ocular
  name: Amblyopia
  description: >-
    Deprivation or refractive amblyopia affecting the better or fellow eye in
    unilateral and asymmetric disease; the principal preventable cause of
    additional visual loss and the reason for early refraction and fellow-eye
    protection.
  phenotype_term:
    preferred_term: Amblyopia
    term:
      id: HP:0000646
      label: Amblyopia
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Protection of the healthy eye in those with"
    explanation: GeneReviews management guidance implying the risk to the fellow eye in unilateral disease; the abstract does not name amblyopia explicitly, so this is scored PARTIAL.
- category: Neurologic
  name: Global developmental delay
  description: >-
    Psychomotor delay is the commonest extraocular feature of SOX2-related A/M
    and occurs across the wider spectrum. Its presence formally reclassifies a
    case as non-isolated, which is precisely why it must be actively sought in
    apparently isolated disease.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "34% had systemic involvement, most"
    explanation: Quantifies systemic involvement, most frequently intellectual/developmental delay, in a prospective MAC cohort.
- category: Neurologic
  name: Hypoplasia of the corpus callosum
  description: >-
    Midline forebrain malformation, the commonest neuroimaging abnormality in
    paediatric A/M cohorts (6 of 20 scanned children), reflecting the forebrain
    role of the same transcription factors.
  phenotype_term:
    preferred_term: Hypoplasia of the corpus callosum
    term:
      id: HP:0002079
      label: Hypoplasia of the corpus callosum
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:35105264
    reference_title: "Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging demonstrated pathology in 14/20 cases with corpus callosum dysgenesis (6/20) being the most common."
    explanation: Documents corpus callosum dysgenesis as the commonest neuroimaging finding in a paediatric A/M cohort (6/20); the conservative OCCASIONAL band is used.
- category: Endocrine
  name: Hypopituitarism
  description: >-
    Anterior and/or posterior pituitary hormone deficiency. OTX2 is a recognised
    cause of combined pituitary hormone deficiency with eye involvement, and
    truncating RAX variants have caused anophthalmia with congenital
    hypopituitarism and diabetes insipidus.
  phenotype_term:
    preferred_term: Hypopituitarism
    term:
      id: HP:0040075
      label: Hypopituitarism
  evidence:
  - reference: PMID:33950863
    reference_title: The phenotypic spectrum associated with OTX2 mutations in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities"
    explanation: Identifies OTX2 haploinsufficiency in congenital hypopituitarism patients with eye abnormalities.
  - reference: PMID:30811539
    reference_title: "Truncating RAX Mutations: Anophthalmia, Hypopituitarism, Diabetes Insipidus, and Cleft Palate in Mice and Men."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report the case of a child with anophthalmia, congenital"
    explanation: Documents hypopituitarism co-occurring with anophthalmia in a RAX-diagnosed patient.
- category: Endocrine
  name: Hypogonadism
  description: >-
    Gonadal-axis dysfunction, reported among the classical extraocular features
    of SOX2-related disease and attributed to pituitary involvement.
  phenotype_term:
    preferred_term: Hypogonadism
    term:
      id: HP:0000135
      label: Hypogonadism
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hypogonadism and growth retardation, possibly related to pituitary anomalies, and renal"
    explanation: Lists hypogonadism among the common extraocular features of SOX2-related A/M.
- category: Gastrointestinal
  name: Esophageal atresia
  description: >-
    Discontinuity of the oesophagus, with or without tracheo-oesophageal fistula.
    The defining extraocular feature of the anophthalmia-oesophageal-genital
    (AEG) syndrome, OMIM:206900 / MCOPS3, caused by the same SOX2 variants that
    cause apparently isolated A/M in other individuals.
  phenotype_term:
    preferred_term: Esophageal atresia
    term:
      id: HP:0002032
      label: Esophageal atresia
  frequency: VERY_RARE
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rarely patients may also display esophageal atresia"
    explanation: Documents oesophageal atresia as a rare extraocular feature of SOX2-related A/M, supporting the VERY_RARE band.
genetic:
- name: SOX2
  gene_term:
    preferred_term: SOX2
    term:
      id: hgnc:11195
      label: SOX2
  relationship_type: CAUSATIVE
  frequency: 10-15% of all anophthalmia/microphthalmia
  notes: >-
    Autosomal dominant. The single commonest genetic cause of A/M. Heterozygous
    loss-of-function variants, including whole-gene deletions (which account for
    25-50% of pathogenic SOX2 alleles), reduce dosage of this pluripotency and
    eye-field transcription factor. The ocular phenotype is classically bilateral
    and severe, with anophthalmia in the majority. Most variants are de novo but
    germline mosaicism is documented. OMIM classifies SOX2 A/M in the SYNDROMIC
    MCOPS3 series (anophthalmia/microphthalmia-oesophageal atresia syndrome,
    OMIM:206900), not the isolated MCOP series — a direct reflection of its
    frequent extraocular involvement.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SOX2 pathogenic variants, including whole gene deletions, are present in 10-15% of all A/M patients"
    explanation: Quantifies the SOX2 contribution to A/M.
  - reference: PMID:30450772
    reference_title: "Extension of the mutational and clinical spectrum of SOX2 related disorders: Description of six new cases and a novel association with suprasellar teratoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Heterozygous loss-of-function variants in SOX2 are identified in approximately 40% of all"
    explanation: Quantifies the much higher SOX2 yield specifically in bilateral A/M.
- name: OTX2
  gene_term:
    preferred_term: OTX2
    term:
      id: hgnc:8522
      label: OTX2
  relationship_type: CAUSATIVE
  frequency: 0.7-10% of anophthalmia/microphthalmia
  notes: >-
    Autosomal dominant. The second commonest dominant cause. Truncating, missense
    and whole-gene deletion alleles (deletions being 30-40% of variants) reduce
    dosage of this homeobox transcription factor. The ocular phenotype ranges
    from bilateral anophthalmia through Leber congenital amaurosis to no ocular
    malformation even within one family, making counselling difficult. OTX2 is
    expressed in the posterior pituitary, retina, ear, thalamus and choroid
    plexus during human embryogenesis, which underlies the characteristic
    pituitary-plus-eye phenotype; OMIM assigns it to the syndromic MCOPS5 series
    (OMIM:610125).
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The ocular phenotype of patients with pathogenic OTX2 variants is highly variable even within the"
    explanation: Documents the marked variability of OTX2 ocular expressivity.
  - reference: PMID:33950863
    reference_title: The phenotypic spectrum associated with OTX2 mutations in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree."
    explanation: Establishes the coupled pituitary-eye phenotype and the variable penetrance of OTX2 disease.
- name: RAX
  gene_term:
    preferred_term: RAX
    term:
      id: hgnc:18662
      label: RAX
  relationship_type: CAUSATIVE
  frequency: approximately 3% of anophthalmia/microphthalmia
  notes: >-
    Autosomal recessive. Biallelic (homozygous or compound heterozygous) variants
    in this paired-type homeobox gene cause bilateral microphthalmia or
    anophthalmia, often with sclerocornea. RAX patterns the ventral forebrain and
    hypothalamus as well as the eye; truncating alleles have produced
    anophthalmia together with congenital hypopituitarism, diabetes insipidus and
    cleft palate, so a RAX diagnosis should not be assumed to be ocularly
    isolated. Corresponds to MCOP3 (MONDO:0012604, OMIM:611038).
  evidence:
  - reference: PMID:30811539
    reference_title: "Truncating RAX Mutations: Anophthalmia, Hypopituitarism, Diabetes Insipidus, and Cleft Palate in Mice and Men."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, homozygous or compound heterozygous RAX mutations have been reported to cause bilateral microphthalmia or anophthalmia without consistent associated features."
    explanation: Establishes the recessive RAX mechanism and its ocular phenotype.
- name: VSX2
  gene_term:
    preferred_term: VSX2
    term:
      id: hgnc:1975
      label: VSX2
  relationship_type: CAUSATIVE
  notes: >-
    Autosomal recessive. Biallelic VSX2 (CHX10) variants cause bilateral
    microphthalmia, particularly in consanguineous pedigrees. Reported alleles
    disrupt the homeodomain or the conserved CVC motif required for DNA binding
    and transcriptional repression, impairing retinal-progenitor specification
    and de-repressing the RPE programme. Corresponds to MCOP2 (MONDO:0012409) and
    MCOPCB3 (MONDO:0012408).
  evidence:
  - reference: PMID:21976963
    reference_title: VSX2 mutations in autosomal recessive microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Homozygous mutations in VSX2 were identified in two out of five"
    explanation: Directly documents biallelic VSX2 variants in consanguineous families with isolated microphthalmia.
- name: ALDH1A3
  gene_term:
    preferred_term: ALDH1A3
    term:
      id: hgnc:409
      label: ALDH1A3
  relationship_type: CAUSATIVE
  notes: >-
    Autosomal recessive. Biallelic variants in retinaldehyde dehydrogenase 3
    block the final step of retinoic acid synthesis. Every affected individual
    across seven reported families had bilateral A/M, with variably present
    intellectual disability, developmental delay, autism, seizures and facial
    dysmorphism — again illustrating that the "isolated" designation is
    provisional. Corresponds to MCOP8 (MONDO:0014050, OMIM:615113).
  evidence:
  - reference: PMID:36997679
    reference_title: Clinical and genetic analysis further delineates the phenotypic spectrum of ALDH1A3-related anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All affected individuals had bilateral anophthalmia/microphthalmia (A/M), three with additional intellectual or developmental delay, one with autism and seizures and three with facial dysmorphic features."
    explanation: Establishes the fully penetrant ocular phenotype and the variable neurodevelopmental extension.
  - reference: PMID:24024553
    reference_title: A homozygous mutation in a consanguineous family consolidates the role of ALDH1A3 in autosomal recessive microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified a novel homozygous missense mutation in ALDH1A3 using exome sequencing"
    explanation: Independent confirmation of the recessive ALDH1A3 mechanism.
- name: FOXE3
  gene_term:
    preferred_term: FOXE3
    term:
      id: hgnc:3808
      label: FOXE3
  relationship_type: CAUSATIVE
  frequency: approximately 2.5% of anophthalmia/microphthalmia
  notes: >-
    Both dominant and recessive. A forkhead transcription factor of the lens
    placode. Monoallelic variants were first described in dominant
    anterior-segment dysgenesis; biallelic variants cause recessive primary
    aphakia, sclerocornea and microphthalmia. Genotype-phenotype correlations
    exist between mutation type, mode of inheritance and severity.
  evidence:
  - reference: PMID:29136273
    reference_title: "FOXE3 mutations: genotype-phenotype correlations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This review demonstrates that correlations exist between the mutation type, mode of"
    explanation: Establishes the dual dominant/recessive FOXE3 mechanism and its genotype-phenotype structure.
- name: PAX6
  gene_term:
    preferred_term: PAX6
    term:
      id: hgnc:8620
      label: PAX6
  relationship_type: CAUSATIVE
  frequency: approximately 2% of anophthalmia/microphthalmia
  notes: >-
    Autosomal dominant. The master eye-field regulator, best known for aniridia
    but also a recognised lower-frequency cause of A/M and coloboma. A
    heterozygous homeodomain variant was identified in two brothers with
    bilateral microphthalmia, coloboma, primary aphakia, iris hypoplasia,
    sclerocornea and congenital glaucoma, with an apparently mosaic unaffected
    carrier mother — illustrating both the phenotypic breadth and the mosaicism
    that complicates counselling across this spectrum.
  evidence:
  - reference: PMID:26130484
    reference_title: "Novel mutations in PAX6, OTX2 and NDP in anophthalmia, microphthalmia and coloboma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A novel heterozygous likely pathogenic variant in PAX6, c.767T>C,"
    explanation: Documents a pathogenic PAX6 variant in probands with bilateral microphthalmia and coloboma.
- name: MAB21L2
  gene_term:
    preferred_term: MAB21L2
    term:
      id: hgnc:6758
      label: MAB21L2
  relationship_type: CAUSATIVE
  notes: >-
    Both dominant and recessive disease occur. Heterozygous substitutions at
    p.Arg51 cause severe bilateral disease and are proposed to act through a
    dominant-negative mechanism, whereas a homozygous p.Arg247Gln produced a
    milder phenotype in a consanguineous family. Identified among the causal
    genes in a prospective real-world MAC cohort, with a novel association with
    unilateral microphthalmia.
  evidence:
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "New phenotypic associations were found for FOXE3 (bilateral sensorineural hearing loss) and MAB21L2 (unilateral microphthalmia)."
    explanation: Documents MAB21L2 as a causal MAC gene with a newly described unilateral microphthalmia association.
- name: GDF6
  gene_term:
    preferred_term: GDF6
    term:
      id: hgnc:4221
      label: GDF6
  relationship_type: CAUSATIVE
  frequency: approximately 1 percent of A/M and coloboma patients screened
  notes: >-
    Autosomal dominant. A BMP-family TGF-beta signalling ligand that regulates
    developmental patterning. All reported pathogenic GDF6 variants are
    heterozygous missense changes, with affected individuals showing ocular
    anomalies, skeletal anomalies, or both; the ocular range extends from
    bilateral anophthalmia to unilateral coloboma. Corresponds to MCOP4
    (MONDO:0013130, OMIM:613094).
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Variants in these genes account for 1.7% and 1% of A/M and coloboma patients screened for GDF3 or GDF6 mutations, respectively"
    explanation: Quantifies the GDF6 (1%) and GDF3 (1.7%) contributions to screened A/M and coloboma cohorts.
- name: GDF3
  gene_term:
    preferred_term: GDF3
    term:
      id: hgnc:4218
      label: GDF3
  relationship_type: CAUSATIVE
  frequency: approximately 1.7 percent of A/M and coloboma patients screened
  notes: >-
    Autosomal dominant. The paralogous BMP-family ligand to GDF6, likewise
    causing disease through heterozygous missense variants and likewise
    producing combined ocular and skeletal phenotypes. Corresponds to MCOP7
    (MONDO:0013377, OMIM:613704).
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All of the pathogenic variants reported to date for GDF3 and GDF6 are heterozygous missense changes"
    explanation: Establishes the heterozygous missense mechanism shared by GDF3 and GDF6.
- name: MFRP
  gene_term:
    preferred_term: MFRP
    term:
      id: hgnc:18121
      label: MFRP
  relationship_type: CAUSATIVE
  notes: >-
    Autosomal recessive. Biallelic MFRP variants cause nanophthalmia and
    posterior microphthalmia, sometimes with retinal dystrophy, foveoschisis and
    optic disc drusen. This is the small-eye-with-normal-anterior-segment arm of
    the spectrum, mechanistically distinct from the eye-field transcription
    factor lesions that cause severe A/M. Corresponds to MCOP5 (MONDO:0012605,
    OMIM:611040).
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, biallelic mutations in MFRP were first associated with nanophthalmia (Sundin et al. 2005)."
    explanation: Documents the recessive MFRP mechanism and its nanophthalmia and posterior microphthalmia phenotype.
- name: PRSS56
  gene_term:
    preferred_term: PRSS56
    term:
      id: hgnc:39433
      label: PRSS56
  relationship_type: CAUSATIVE
  notes: >-
    Autosomal recessive. Biallelic PRSS56 variants (missense, nonsense,
    frameshift and splice-donor) cause posterior microphthalmia and
    nanophthalmia in humans and posterior microphthalmia in mice, the second
    gene of the posterior-microphthalmia arm alongside MFRP. Corresponds to
    MCOP6 (MONDO:0013293, OMIM:613517).
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "cause autosomal recessive posterior microphthalmia and nanophthalmia in"
    explanation: Documents the recessive PRSS56 mechanism and its posterior microphthalmia and nanophthalmia phenotype.
- name: Copy-number and chromosomal variants
  relationship_type: CAUSATIVE
  notes: >-
    Chromosomal deletions, duplications and translocations are an important and
    frequently overlooked cause. In a Danish national cohort 14.7% of karyotyped
    A/M and coloboma cases had an abnormal karyotype, and a possibly pathogenic
    copy-number variant was found in 44.4% of those who underwent chromosomal
    microarray — supporting microarray as a first-tier test alongside sequencing.
  evidence:
  - reference: PMID:27552085
    reference_title: Congenital Microphthalmia, Anophthalmia and Coloboma among Live Births in Denmark.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chromosome analysis was performed in 36.1% of the cohort, and 14.7% of cases had an abnormal karyotype."
    explanation: The Danish cohort reports an abnormal karyotype in 14.7% of those analysed, quantifying the chromosomal contribution.
environmental:
- name: Gestationally acquired infection
  influences_mechanisms:
  - target: Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: >-
      This node was written to hold the non-genetic minority of cases, and it
      names gestational infection as the strongest environmental evidence in
      its own text. Recorded as direct because infection disrupts ocular
      tissue during the developmental window itself, which is the node's own
      event rather than something upstream of it. Graded above the other three
      exposures pointing here, on the source's own ranking rather than a
      curatorial preference.
    evidence:
    - reference: PMID:18039390
      reference_title: "Anophthalmia and microphthalmia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"
      explanation: >-
        Ranks gestational infection as the best-evidenced environmental cause,
        ahead of the other three exposures this entry records. Quoted as the
        whole sentence, since it is the comparison between the exposures that
        does the work.
    - reference: PMID:38350011
      reference_title: "Prenatal and Postnatal Ocular Abnormalities Following Congenital Zika Virus Infections: A Systematic Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "microphthalmia was reported in 13 cases (13/479, 2.7%)"
      explanation: >-
        Quantifies microphthalmia in 2.7% of postnatally examined congenital
        Zika cases, giving one infection a measured rate rather than a
        listing.
  description: >-
    Congenital infection during the first trimester is the environmental exposure
    with the strongest evidence for causing A/M. Congenital rubella,
    toxoplasmosis and cytomegalovirus are classically implicated, and congenital
    Zika virus infection produced microphthalmia in 2.7% of a systematic review
    of 479 postnatally examined cases. Infection acts by disrupting or destroying
    ocular tissue during the developmental window; the malformation itself is not
    transmissible.
  presence: PRESENT
  effect: HARMFUL
  evidence:
  - reference: PMID:18039390
    reference_title: Anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The strongest evidence appears to be with gestational-acquired infections"
    explanation: Ranks gestational infection as the best-evidenced environmental cause.
  - reference: PMID:38350011
    reference_title: "Prenatal and Postnatal Ocular Abnormalities Following Congenital Zika Virus Infections: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "microphthalmia was reported in 13 cases (13/479, 2.7%)"
    explanation: Quantifies microphthalmia after congenital Zika virus infection.
- name: Maternal vitamin A deficiency
  exposure_term:
    preferred_term: low maternal vitamin A (retinol) exposure
    modifier: DECREASED
    term:
      id: ECTO:9000128
      label: exposure to all-trans-retinol
  influences_mechanisms:
  - target: Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Graded below the infection link into this same node, because the
      sentence that names both exposures ranks infection first and attaches
      maternal vitamin A deficiency to a hedged may also include. The
      mechanistically specific edge for this exposure is the separate one into
      the retinoic acid node.
    evidence:
    - reference: PMID:18039390
      reference_title: "Anophthalmia and microphthalmia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"
      explanation: >-
        Names maternal vitamin A deficiency among the environmental
        contributors, under a hedge the sentence does not apply to gestational
        infection.
    - reference: PMID:11926054
      reference_title: "Environmental risk factors in congenital malformations of the eye."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Eleven (16%) mothers had a history of night blindness while pregnant with the affected child"
      explanation: >-
        Sixteen percent of mothers in a coloboma series reported night
        blindness during the affected pregnancy. Maternal history rather than
        any measurement of embryonic signalling.
  - target: Retinoic Acid Signalling Deficiency
    environmental_effect: TRIGGERS
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      The substrate-supply edge, and the reason this exposure is graded
      differently from the other three: maternal retinol is the source of the
      embryonic retinoic acid this node is built around, so the intervening
      step is a known one rather than an unknown. Night blindness in the
      mother is a clinical marker of the deficiency and not a measurement of
      embryonic signalling, which is what keeps the evidence partial while the
      link itself is specific.
    evidence:
    - reference: PMID:11926054
      reference_title: "Environmental risk factors in congenital malformations of the eye."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Eleven (16%) mothers had a history of night blindness while pregnant with the affected child"
      explanation: >-
        Maternal night blindness during the affected pregnancy is a clinical
        marker of the vitamin A deficiency that would limit retinoid substrate
        at this node.
  description: >-
    Insufficient maternal retinol restricts the substrate supply for embryonic
    retinoic acid synthesis, converging on the same STRA6/ALDH1A3/RARB pathway
    perturbed by the recessive retinoid-pathway genes. In an Indian case series
    of children with coloboma, 16% of mothers reported night blindness — a
    clinical marker of vitamin A deficiency — during the affected pregnancy.
  presence: PRESENT
  effect: HARMFUL
  evidence:
  - reference: PMID:18039390
    reference_title: Anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "also include maternal vitamin A deficiency"
    explanation: Names maternal vitamin A deficiency among the environmental contributors.
  - reference: PMID:11926054
    reference_title: Environmental risk factors in congenital malformations of the eye.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Eleven (16%) mothers had a history of night blindness while pregnant with the affected child"
    explanation: Provides direct maternal-history evidence linking vitamin A deficiency to congenital eye malformation.
- name: Teratogenic drug exposure
  exposure_term:
    preferred_term: teratogen exposure
    term:
      id: XCO:0000512
      label: teratogen
  influences_mechanisms:
  - target: Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Thalidomide is named in the review sentence, and first-trimester
      medication use is documented in a case series without the agents being
      identified. Not also pointed at the retinoic acid node, although this
      entry's own description makes that argument for systemic retinoids: no
      cited sentence names a retinoid, so the edge would rest on the
      description rather than on evidence.
    evidence:
    - reference: PMID:18039390
      reference_title: "Anophthalmia and microphthalmia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"
      explanation: >-
        Names thalidomide exposure among the environmental contributors, under
        the same hedge as vitamin A deficiency.
    - reference: PMID:11926054
      reference_title: "Environmental risk factors in congenital malformations of the eye."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "seven (8%) took medication during the 1st trimester"
      explanation: >-
        Eight percent of mothers took medication in the first trimester. The
        agents are not all identified, so this supports an exposure class
        rather than a drug.
  description: >-
    Thalidomide is the classically documented ocular teratogen in this spectrum.
    Systemic retinoids (isotretinoin and related compounds) are potent teratogens
    acting directly on the retinoic-acid signalling node, which is why
    contraception is mandatory during treatment; retinoid excess and vitamin A
    deficiency perturb the same pathway from opposite directions.
    First-trimester medication use was documented in 8% of mothers in an Indian
    coloboma series.
  presence: PRESENT
  effect: HARMFUL
  chemicals:
  - thalidomide
  - isotretinoin
  evidence:
  - reference: PMID:18039390
    reference_title: Anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "exposure to X-rays, solvent misuse and thalidomide exposure"
    explanation: Names thalidomide among the environmental contributors to A/M.
  - reference: PMID:11926054
    reference_title: Environmental risk factors in congenital malformations of the eye.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "seven (8%) took medication during the 1st trimester"
    explanation: Documents first-trimester medication exposure in mothers of affected children; the specific agents are not all identified, so this is scored PARTIAL.
- name: Ionising radiation and solvent exposure
  influences_mechanisms:
  - target: Teratogenic and Infectious Disruption of First-Trimester Ocular Morphogenesis
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      X-rays and solvent misuse are listed in the same hedged clause as the
      other two non-infectious exposures and are graded identically to them.
      The supporting case-series figure is about agricultural chemicals rather
      than about either named exposure, which is a further reason this stays
      partial.
    evidence:
    - reference: PMID:18039390
      reference_title: "Anophthalmia and microphthalmia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The strongest evidence appears to be with gestational-acquired infections, but may also include maternal vitamin A deficiency, exposure to X-rays, solvent misuse and thalidomide exposure"
      explanation: >-
        Names exposure to X-rays and solvent misuse among the environmental
        contributors.
    - reference: PMID:11926054
      reference_title: "Environmental risk factors in congenital malformations of the eye."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "11 (13%) reported exposure to agricultural chemicals"
      explanation: >-
        Thirteen percent of mothers reported agricultural chemical exposure.
        Observational, unadjusted, and about a different chemical class than
        the two this exposure names.
  description: >-
    Exposure to X-rays and organic-solvent misuse during early pregnancy are
    listed among the environmental contributors to A/M, although quantitative
    effect estimates specific to isolated A/M are not available. Agricultural
    chemical exposure was reported by 13% of mothers in an Indian coloboma
    series.
  presence: PRESENT
  effect: HARMFUL
  evidence:
  - reference: PMID:18039390
    reference_title: Anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "exposure to X-rays, solvent misuse"
    explanation: Names ionising radiation and solvent exposure among the recognised environmental contributors.
  - reference: PMID:11926054
    reference_title: Environmental risk factors in congenital malformations of the eye.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "11 (13%) reported exposure to agricultural chemicals"
    explanation: Documents chemical exposure in mothers of children with congenital eye malformation; the association is observational and unadjusted, so this is scored PARTIAL.
treatments:
- name: Serial conformer-assisted socket expansion
  description: >-
    The principal disease-directed intervention. Because orbital, conjunctival
    and eyelid growth is normally driven by the expanding globe, an ocularist
    fits conformers of progressively increasing size starting shortly after birth
    to expand the palpebral fissure, conjunctival cul-de-sac and bony orbit. In a
    24-orbit case series with a mean of 7 conformer exchanges over 51 months,
    good outcomes were achieved in 18 orbits (75%) and fair outcomes in 6 (25%),
    with unilateral cases reaching a mean final lid length of 22.3 mm against
    23.5 mm in the normal contralateral eye.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  target_mechanisms:
  - target: Failure of Orbital and Periocular Growth
    treatment_effect: BYPASSES
    description: >-
      Conformers supply mechanically the expansile stimulus that the absent or
      small globe cannot, driving orbital and palpebral growth by an external
      route rather than restoring globe development.
  target_phenotypes:
  - preferred_term: Blepharophimosis
    term:
      id: HP:0000581
      label: Blepharophimosis
  evidence:
  - reference: PMID:36257503
    reference_title: Socket expansion with conformers in congenital anophthalmia and microphthalmia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Good outcomes were achieved in 18 orbits (75%); fair outcomes, in 6 (25%) cases."
    explanation: The case series reports good outcomes in 18 of 24 orbits (75%) after conformer-assisted socket expansion.
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an ocularist can start shortly after birth to expand the palpebral fissures"
    explanation: GeneReviews management recommendation establishing timing and rationale.
- name: Ocular prosthesis
  description: >-
    Fitting of an ocular prosthesis over the socket or a microphthalmic globe.
    GeneReviews states directly that prosthetic intervention is appropriate for
    those with severe microphthalmia and anophthalmia; it is the most universal
    intervention in this disorder, addressing both cosmesis and, together with
    conformers, socket volume. In a prospective MAC cohort most patients did not
    require a customised prosthesis, so the need is individualised rather than
    universal across the whole spectrum.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  target_mechanisms:
  - target: Failure of Orbital and Periocular Growth
    treatment_effect: BYPASSES
    description: >-
      A prosthesis occupies and maintains socket volume in place of the absent
      or hypoplastic globe.
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prosthetic intervention is appropriate for those with severe microphthalmia and anophthalmia."
    explanation: GeneReviews management recommendation for prosthetic intervention.
- name: Oculoplastic and orbital reconstructive surgery
  description: >-
    Surgical intervention for severe sockets, orbital cysts and prosthetic
    support. GeneReviews advises that an oculoplastic surgeon determine the most
    suitable options after age six months, when postnatal orbital growth can be
    assessed, and before orbital dimensions become fixed — after which far more
    extensive reconstruction is required. This timing constraint is the key
    management point.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Ophthalmologic Surgical Procedure
    term:
      id: NCIT:C15331
      label: Ophthalmologic Surgical Procedure
  target_mechanisms:
  - target: Failure of Orbital and Periocular Growth
    treatment_effect: BYPASSES
    description: >-
      Orbital reconstruction and implants substitute surgically for the missing
      globe-driven expansion of the socket.
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An oculoplastic surgeon can help determine the most suitable options for"
    explanation: GeneReviews surgical timing guidance for orbital reconstruction.
- name: Low-vision rehabilitation and early developmental intervention
  description: >-
    Children with reduced vision benefit from visual aids and visual resources,
    together with early intervention to optimise psychomotor development,
    education, life skills and mobility. Orientation and mobility training is
    central for bilateral visual loss. Quality of life is measurably reduced:
    median parent-reported PedsQL total score was 52.4 in affected children aged
    2-12.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  target_phenotypes:
  - preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Children with reduced vision may benefit from visual aids and other visual resources as well as early"
    explanation: GeneReviews rehabilitation recommendation.
  - reference: PMID:35105264
    reference_title: "Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The median total PedsQL score of parent reports for ages 2-12 was 52.4 (range 22.6-100)."
    explanation: Quantifies the quality-of-life impairment that rehabilitation addresses.
- name: Protection of the fellow eye
  description: >-
    In unilateral disease the unaffected eye carries the individual's entire
    visual function, so protective polycarbonate eyewear, prompt refraction and
    amblyopia treatment are explicitly recommended. This is the highest-yield,
    lowest-cost intervention in unilateral A/M.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Amblyopia
    term:
      id: HP:0000646
      label: Amblyopia
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Protection of the healthy eye in those with"
    explanation: GeneReviews management recommendation for unilateral disease.
- name: Genetic counselling and molecular diagnosis
  description: >-
    Molecular testing identifies a genetic cause in 80% of individuals with
    bilateral anophthalmia or severe microphthalmia and up to 20% of all MAC
    individuals, and should combine sequencing with gene-targeted
    deletion/duplication analysis and chromosomal microarray. Real-world yields
    are meaningful in unilateral as well as bilateral disease (33% in each group
    in a prospective cohort), so testing should not be restricted to bilateral
    cases. Counselling must address de novo occurrence, incomplete penetrance,
    variable expressivity and germline mosaicism, which together mean recurrence
    risk after an apparently de novo diagnosis is not zero.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "can identify a genetic cause in 80% of individuals with"
    explanation: GeneReviews diagnostic-yield figure underpinning the testing recommendation.
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a molecular diagnostic rate of 33% for both bilateral and unilateral cohorts"
    explanation: Supports extending genetic testing to unilateral cases.
- name: Management of secondary ocular complications
  description: >-
    Remediable pathology in the malformed or fellow eye should be treated
    actively: cataract extraction, glaucoma control, and retinal-detachment
    repair. Retinal detachment occurred in 9% of a prospective MAC cohort and
    presented from the first to the third decade, so lifelong surveillance rather
    than a fixed discharge point is appropriate.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Ophthalmologic Surgical Procedure
    term:
      id: NCIT:C15331
      label: Ophthalmologic Surgical Procedure
  target_phenotypes:
  - preferred_term: Cataract
    term:
      id: HP:0000518
      label: Cataract
  - preferred_term: Glaucoma
    term:
      id: HP:0000501
      label: Glaucoma
  - preferred_term: Retinal detachment
    term:
      id: HP:0000541
      label: Retinal detachment
  evidence:
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study highlights the importance of thorough clinical and molecular phenotyping of MAC patients to provide appropriate multidisciplinary care."
    explanation: Establishes the multidisciplinary phenotyping and management model within which secondary complications are detected and treated.
diagnosis:
- name: Ophthalmic examination with axial-length biometry
  description: >-
    Diagnosis begins with comprehensive paediatric ophthalmological examination:
    inspection for any globe tissue, corneal diameter, axial length by
    ultrasound biometry, anterior- and posterior-segment examination where
    possible, refraction, intraocular pressure and visual behaviour, together
    with full assessment of the fellow eye. Microphthalmia is confirmed when
    total axial length is more than 2 SD below the age-adjusted mean (<21 mm in
    adults, <14 mm in newborns); severe microphthalmia additionally requires a
    corneal diameter under 4 mm.
  diagnosis_term:
    preferred_term: Eye Examination
    term:
      id: NCIT:C38060
      label: Eye Examination
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "deviations (SD) below the age-adjusted population mean; < 21 mm in adults and < 14 mm in newborns"
    explanation: Gives the biometric threshold on which the clinical diagnosis rests.
- name: Orbital and cranial magnetic resonance imaging
  description: >-
    Orbital imaging distinguishes a truly absent globe from extreme
    microphthalmia, an orbital cyst or another orbital lesion, and is
    particularly indicated in bilateral severe disease, developmental delay,
    seizures, optic-nerve abnormality or suspected midline and pituitary
    involvement. In a paediatric A/M cohort neuroimaging was abnormal in 14 of
    20 scanned children, corpus callosum dysgenesis being commonest.
  diagnosis_term:
    preferred_term: Magnetic Resonance Imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  evidence:
  - reference: PMID:35105264
    reference_title: "Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging demonstrated pathology in 14/20 cases with corpus callosum dysgenesis (6/20) being the most common."
    explanation: Quantifies the yield of neuroimaging in a paediatric A/M cohort.
- name: Chromosomal microarray analysis
  description: >-
    First-tier cytogenetic testing. Chromosomal aberrations are a substantial
    and easily missed cause: in a Danish national cohort 14.7% of karyotyped
    cases had an abnormal karyotype, and among the 8.7% who underwent
    chromosomal microarray a possibly pathogenic copy-number variant was found
    in 44.4%.
  diagnosis_term:
    preferred_term: Microarray Analysis
    term:
      id: NCIT:C18477
      label: Microarray Analysis
  evidence:
  - reference: PMID:27552085
    reference_title: Congenital Microphthalmia, Anophthalmia and Coloboma among Live Births in Denmark.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In 8.7% of the cohort, a chromosome microarray analysis was performed, and in 44.4% of cases, a possibly pathogenic copy number variation was observed."
    explanation: Quantifies the copy-number yield that justifies microarray as a first-tier test.
- name: Exome or genome sequencing
  description: >-
    Molecular genetic testing identifies a cause in 80% of individuals with
    bilateral anophthalmia or severe microphthalmia and up to 20% of all MAC
    individuals, and should combine sequence analysis with gene-targeted
    deletion/duplication analysis. Clinical exome sequencing achieved a
    diagnostic rate starting at 32.3% in a 189-person non-isolated MAC cohort,
    and a subset of the implicated genes are absent from commercially available
    ophthalmic gene panels - an argument for exome or genome sequencing rather
    than panel testing. Real-world yield is comparable in unilateral and
    bilateral disease (33% each), so testing should not be restricted to
    bilateral cases.
  diagnosis_term:
    preferred_term: Whole Exome Sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "can identify a genetic cause in 80% of individuals with bilateral anophthalmia/severe microphthalmia and in up to 20% of all individuals with an ocular malformation in the MAC spectrum."
    explanation: GeneReviews diagnostic-yield benchmark.
  - reference: PMID:38502138
    reference_title: "High Clinical Exome Sequencing Diagnostic Rates and Novel Phenotypic Expansions for Nonisolated Microphthalmia, Anophthalmia, and Coloboma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We found the efficacy of cES in nonisolated MAC to be between 32.3%"
    explanation: Contemporary clinical-exome diagnostic rate in a large MAC cohort.
  - reference: PMID:36192130
    reference_title: Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a molecular diagnostic rate of 33% for both bilateral and unilateral cohorts"
    explanation: Shows comparable yield in unilateral disease, supporting unrestricted testing.
differential_diagnoses:
- name: Microphthalmia with coloboma
  description: >-
    The immediate MONDO child term (MONDO:0000170) and the fissure-closure arm of
    the same spectrum, curated in dismech as `Microphthalmia_with_Coloboma`.
    Distinguished from non-colobomatous A/M by the presence of a demonstrable
    iris, chorioretinal or optic-disc coloboma. This is a boundary rather than a
    rival diagnosis: colobomatous microphthalmia is a subset of this entity.
  disease_term:
    preferred_term: microphthalmia, isolated, with coloboma
    term:
      id: MONDO:0000170
      label: microphthalmia, isolated, with coloboma
  distinguishing_features:
  - Demonstrable coloboma of iris, retina, choroid or optic disc.
  - Mechanistically attributable to step 3 (optic fissure closure) rather than step 1 or 2.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "optic fissure closure defect, it is referred to as colobomatous microphthalmia"
    explanation: Defines the boundary between colobomatous and non-colobomatous microphthalmia.
- name: STRA6-related syndromic microphthalmia (Matthew-Wood syndrome)
  description: >-
    Biallelic STRA6 variants disrupt cellular retinol uptake, causing
    anophthalmia or microphthalmia together with pulmonary hypoplasia or
    agenesis, diaphragmatic defects and cardiac malformations (PDAC/MCOPS9,
    OMIM:601186). Shares the retinoic-acid mechanism with isolated A/M but is
    distinguished by the extraocular malformation pattern. Curated separately as
    `STRA6-related_syndromic_microphthalmia`.
  disease_term:
    preferred_term: Matthew-Wood syndrome
    term:
      id: MONDO:0011010
      label: Matthew-Wood syndrome
  distinguishing_features:
  - Pulmonary hypoplasia or agenesis.
  - Diaphragmatic hernia or eventration.
  - Congenital cardiac malformation.
  - Biallelic STRA6 variants rather than SOX2 or OTX2 dosage loss.
  evidence:
  - reference: PMID:30762128
    reference_title: "Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "STRA6 codes for a transmembrane receptor that mediates the cellular uptake of Vitamin A (retinol)."
    explanation: Establishes the STRA6 retinol-uptake mechanism that distinguishes this syndromic differential.
- name: RARB-related syndromic microphthalmia (MCOPS12)
  description: >-
    Predominantly de novo gain-of-function RARB variants produce a
    Matthew-Wood-like malformation pattern (pulmonary and diaphragmatic defects,
    A/M, cardiac malformation) with severe global developmental delay and
    progressive movement disorder. Also a retinoic-acid-pathway disorder but
    acting at the receptor rather than at synthesis or uptake. Curated separately
    as `RARB-related_syndromic_microphthalmia`.
  disease_term:
    preferred_term: microphthalmia, syndromic 12
    term:
      id: MONDO:0014229
      label: microphthalmia, syndromic 12
  distinguishing_features:
  - Progressive spasticity, dystonia or chorea.
  - Pulmonary and diaphragmatic malformation.
  - Gain-of-function RARB variants.
- name: CHARGE syndrome
  description: >-
    CHD7-related multisystem disorder in which ocular coloboma is a cardinal
    feature, accompanied by choanal atresia, cranial nerve dysfunction,
    characteristic ear anomalies and hearing loss, cardiac defects and growth
    retardation. Should be considered whenever coloboma co-occurs with any of
    these. Curated separately as `CHARGE_Syndrome`.
  disease_term:
    preferred_term: CHARGE syndrome
    term:
      id: MONDO:0008965
      label: CHARGE syndrome
  distinguishing_features:
  - Choanal atresia and characteristic external ear anomalies.
  - Cranial nerve dysfunction, especially anosmia and swallowing difficulty.
  - Pathogenic CHD7 variant.
- name: Axenfeld-Rieger syndrome
  description: >-
    Anterior-segment dysgenesis with iris hypoplasia, corectopia, posterior
    embryotoxon and a high risk of glaucoma, caused chiefly by PITX2 or FOXC1
    variants and often with dental and umbilical anomalies. Overlaps the
    complex-microphthalmia phenotype at the anterior segment, but the globe is
    usually of normal size. Curated separately as `Axenfeld-Rieger_syndrome`.
  disease_term:
    preferred_term: Axenfeld-Rieger syndrome
    term:
      id: MONDO:0019187
      label: Axenfeld-Rieger syndrome
  distinguishing_features:
  - Normal axial length with isolated anterior-segment dysgenesis.
  - Dental hypoplasia and redundant periumbilical skin.
  - PITX2 or FOXC1 variants.
- name: Congenital cystic eye
  description: >-
    Complete failure of optic vesicle invagination leaving a cystic orbital mass
    with no recognisable globe. Clinically mimics anophthalmia, and a
    colobomatous cyst arising from an incompletely closed optic fissure can
    likewise dominate the orbit alongside a small globe. Orbital ultrasound or
    MRI distinguishes these and directs surgical planning.
  disease_term:
    preferred_term: congenital cystic eye
    term:
      id: MONDO:0022825
      label: congenital cystic eye
  distinguishing_features:
  - Cystic orbital mass on ultrasound or MRI.
  - Absence of any recognisable globe structure.
- name: Fraser syndrome (cryptophthalmos)
  description: >-
    Failure of eyelid separation with skin running continuously over a malformed
    globe, most often as part of Fraser syndrome with cutaneous syndactyly and
    renal agenesis. Clinically resembles anophthalmia because no eye is visible,
    but the adnexa are abnormal rather than preserved — the key discriminator
    from clinical anophthalmia, whose definition explicitly requires intact
    adnexa.
  disease_term:
    preferred_term: Fraser syndrome
    term:
      id: MONDO:0009046
      label: Fraser syndrome
  distinguishing_features:
  - Absent palpebral fissure with skin continuous over the orbit.
  - Cutaneous syndactyly and renal agenesis.
  evidence:
  - reference: PMID:20301552
    reference_title: "Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anophthalmia refers to complete absence of the globe in the presence of ocular adnexa (eyelids, conjunctiva, and lacrimal apparatus)."
    explanation: The requirement for intact ocular adnexa in the definition of anophthalmia is what distinguishes it from cryptophthalmos.
- name: Congenital rubella syndrome and other acquired destructive ocular disease
  description: >-
    A shrunken, disorganised globe following intrauterine infection,
    inflammation, trauma, retinopathy of prematurity or intraocular tumour can be
    mistaken for congenital microphthalmia. Congenital rubella is the classic
    infectious cause, producing cataract, retinopathy and microphthalmia together
    with deafness and cardiac defects; congenital Zika virus infection produced
    microphthalmia in 2.7% of reviewed cases. Serology, laterality, corneal
    diameter relative to axial length, and imaging for calcification or scarring
    distinguish an acquired small eye from a developmental one.
  disease_term:
    preferred_term: congenital rubella syndrome
    term:
      id: MONDO:0017361
      label: congenital rubella syndrome
  distinguishing_features:
  - Positive maternal or infant serology for a TORCH pathogen.
  - Intraocular calcification, chorioretinal scarring or disorganisation on imaging.
  - Accompanying sensorineural deafness and cardiac defects in congenital rubella.
  evidence:
  - reference: PMID:38350011
    reference_title: "Prenatal and Postnatal Ocular Abnormalities Following Congenital Zika Virus Infections: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "microphthalmia was reported in 13 cases (13/479, 2.7%)"
    explanation: Documents a destructive congenital infection producing microphthalmia, the principal acquired mimic.

📚

References & Deep Research

References

PMID:20301552

Microphthalmia/Anophthalmia/Coloboma Spectrum – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY.

No top-level findings curated for this source.

Deep Research

Falcon ▸

Isolated Anophthalmia–Microphthalmia Syndrome: Research Report

Edison Scientific Literature 40 citations 2026-08-01T07:28:09.787326

Isolated Anophthalmia–Microphthalmia Syndrome: Research Report

Executive summary and scope

Isolated anophthalmia–microphthalmia (A/M) is not one molecularly uniform syndrome. It is a phenotypic category within the microphthalmia–anophthalmia–coloboma (MAC) spectrum in which the principal recognized abnormalities are ocular. The same causal gene—and sometimes the same variant—may cause isolated disease in one person and systemic disease in another because of incomplete penetrance, mosaicism, and variable expressivity. “Isolated” should therefore be treated as an ascertainment-time phenotype qualifier rather than proof that extraocular manifestations can never occur.

Anophthalmia denotes absent ocular tissue; clinically, it is usually defined as no visible globe, although microscopic remnants can distinguish extreme microphthalmia from true anophthalmia. Microphthalmia is a structurally small eye with axial length at least 2 standard deviations below the age-adjusted mean. Suggested thresholds are <14 mm in a newborn and <21 mm in an adult; a prospective clinic used <16 mm at birth, <19 mm at 12 months, and <21 mm in adults. “Simple” microphthalmia has otherwise preserved architecture, whereas “complex” microphthalmia includes other anterior- or posterior-segment abnormalities. Severe microphthalmia has been defined by corneal diameter <4 mm plus axial length <10 mm at birth or <12 mm after one year. (plaisancie2019geneticsofanophthalmia pages 2-3, plaisancie2019geneticsofanophthalmia pages 1-2, harding2023realworldclinicaland pages 2-3)

The combined A/M prevalence is approximately 1–3 per 10,000 live births, with broader MAC estimates of 1–4 per 10,000. A/M accounts for an estimated 3–12% of childhood visual impairment, and MAC may contribute up to 15% of childhood blindness worldwide. These estimates combine isolated and syndromic cases and vary by surveillance system. (plaisancie2019geneticsofanophthalmia pages 2-3, harding2023realworldclinicaland pages 1-2)

domain	key finding	quantitative evidence	suggested ontology terms	evidence/source year
disease scope	Isolated anophthalmia-microphthalmia is best treated as a congenital phenotype spectrum within MAC; “isolated/non-syndromic” is a phenotype qualifier, not a single molecular disorder, and many causative genes also produce syndromic disease	Combined MAC prevalence ~1–4/10,000 live births; A/M contributes 3–12% of childhood visual impairment/blindness estimates in reviews/cohorts	anophthalmia, microphthalmia, congenital eye malformation, non-syndromic phenotype qualifier	2019–2023 (plaisancie2019geneticsofanophthalmia pages 2-3, harding2023realworldclinicaland pages 1-2)
definitions	Anophthalmia = absence of visible globe/eye tissue; microphthalmia = axial length ≥2 SD below age-adjusted mean; severe microphthalmia includes very short axial length and small cornea	Adult axial length <21 mm; newborn <14 mm in one review, and operational clinic thresholds <16 mm at birth, <19 mm at 12 months, <21 mm in adults in a prospective cohort	HP:0000528 Anophthalmia; HP:0000568 Microphthalmia; severe microphthalmia; simple microphthalmia; complex microphthalmia	2019, 2023 (plaisancie2019geneticsofanophthalmia pages 1-2, harding2023realworldclinicaland pages 2-3)
onset/natural history	Disorder is congenital and usually recognized neonatally/infancy; laterality is variable and asymmetry is common	Mean cohort age 13 years in prospective MAC clinic; severe forms present at birth; both unilateral and bilateral disease occur	congenital onset, unilateral, bilateral, asymmetric involvement	2019, 2023 (plaisancie2019geneticsofanophthalmia pages 2-3, harding2023realworldclinicaland pages 2-3)
major ocular phenotypes	Core phenotype is absent or small eye; additional ocular anomalies may occur even in apparently isolated cases, especially coloboma, cataract, glaucoma, retinal dystrophy/detachment	In a prospective cohort, 44% had complex ocular features; retinal detachment 9%; no diagnosis in exclusive coloboma subgroup in that cohort	HP:0000528 Anophthalmia; HP:0000568 Microphthalmia; coloboma; cataract; glaucoma; retinal detachment	2019, 2023 (harding2023realworldclinicaland pages 9-10, harding2023realworldclinicaland pages 8-9, plaisancie2019geneticsofanophthalmia pages 6-8)
non-ocular qualifier	“Isolated” requires absence of extra-ocular findings at ascertainment, but some genes show incomplete penetrance/variable expressivity so systemic findings may emerge or be subtle	In a pediatric cohort, isolated A/M occurred in 16/35, while 19/35 had somatic/psychomotor/neuroradiologic/genetic pathology	non-syndromic, syndromic, variable expressivity, incomplete penetrance	2022 (fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)
core genes: AD	Major dominant genes include SOX2 and OTX2; both are dosage-sensitive developmental transcription factors and may cause isolated or syndromic disease	SOX2: 10–15% of all A/M, 15–40% of bilateral severe AM; OTX2: ~0.7–10% or 2–8% of AM in reviews; SOX2+OTX2 together account for ≥60% of bilateral severe cases in one review	SOX2, OTX2, haploinsufficiency, autosomal dominant, de novo, mosaicism	2019 (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 6-8, plaisancie2019geneticsofanophthalmia pages 5-6)
core genes: AR	Important recessive genes include RAX, VSX2, ALDH1A3, and some MAB21L2 cases; these often present with bilateral severe disease	RAX biallelic variants: ~2–3% of AM; ALDH1A3 responsible for ~11% of recessively inherited severe developmental eye anomalies; all 9 affected individuals in Kesim 2023 had bilateral A/M	RAX, VSX2, ALDH1A3, MAB21L2, autosomal recessive, bilateral severe A/M	2019–2023 (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 6-8, plaisancie2019geneticsofanophthalmia pages 9-11, kesim2023clinicalandgenetic pages 1-2)
additional genes / CNVs	Other genes and copy-number changes contribute, including FOXE3, PAX6, BMP7, BCOR, KMT2D, EPHA2, MAB21L2 and large deletions; some are more often syndromic but can appear in isolated MAC presentations	Prospective cohort solved cases involved SOX2, PAX6, KMT2D, EPHA2, MAB21L2, ALDH1A3, BCOR, FOXE3 plus deletions on chromosomes 10, 11 and X; chromosomal anomalies reported up to ~15% overall	FOXE3, PAX6, BMP7, BCOR, KMT2D, EPHA2, CNV, chromosomal deletion	2019, 2023 (harding2023realworldclinicaland pages 1-2, harding2023realworldclinicaland pages 9-10, harding2023realworldclinicaland pages 8-9, plaisancie2019geneticsofanophthalmia pages 9-11)
inheritance nuances	De novo disease, parental mosaicism, incomplete penetrance, and variable expressivity are common and complicate counseling; unilateral vs bilateral severity can differ within gene/family	SOX2 mostly de novo with parental mosaicism reported; OTX2 ~50% de novo with high non-penetrance; MAB21L2 shows AD and AR examples with dominant-negative effect proposed for monoallelic missense variants	incomplete penetrance, variable expressivity, gonosomal mosaicism, dominant negative, haploinsufficiency	2019 (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 6-8, plaisancie2019geneticsofanophthalmia pages 9-11)
developmental pathways	Core upstream mechanism is disruption of eye-field specification and optic vesicle/cup morphogenesis involving SOX2-OTX2-RAX/PAX6/SIX3 networks, SHH patterning, WNT/FGF balance, BMP signaling, and retinoic acid metabolism	Reviews identify conserved transcription factor and signaling pathway modules rather than a single pathway; PTCH1 variants may contribute up to 10% of ocular developmental anomalies in one sequencing study	eye field specification, optic vesicle formation, optic cup morphogenesis, SHH signaling, WNT signaling, BMP signaling, retinoic acid signaling	2015–2020 (dash2020themastertranscription pages 3-3, eintracht2020theuseof pages 7-8, reis2015conservedgeneticpathways pages 28-29)
mechanistic examples	SOX2/OTX2 coregulate RAX; PTCH1 links SOX2 network to SHH; ALDH1A3 and STRA6 impair retinoic acid biology; VSX2 loss shifts neural retina toward RPE fate with WNT upregulation	PTCH1 study estimated contribution up to 10% of ocular developmental anomalies; VSX2 hiPSC optic vesicles showed WNT11/BMP8A up, FGF19 down, and rescue with WNT inhibition in cited model literature	RAX regulation, PTCH1, SHH effector, ALDH1A3, STRA6, neural retina, retinal pigment epithelium	2016–2020 (jackson2020moleculardiagnosticchallenges pages 9-10, eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20, eintracht2020theuseof pages 7-8)
anatomy / tissues / cells	Primary structures affected are globe, optic vesicle/cup, neuroretina, retinal pigment epithelium, lens placode, and ventral optic cup; retinal progenitor cells are a key implicated cell population	ALDH1A3/Raldh3 knockout data support ventral retina shortening; RAX and VSX2 are tied to retinal progenitor establishment/specification	eye globe, optic vesicle, optic cup, neuroretina, retinal pigment epithelium, lens placode, retinal progenitor cell	2019–2020 (plaisancie2019geneticsofanophthalmia pages 6-8, eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20)
epidemiology / demographics	Rare congenital disorder spectrum with variable ascertainment by registry and clinic; childhood blindness burden is substantial	Prevalence estimates range ~1–3 or 1–4 per 10,000 live births; one prospective clinic cohort was 60% female but not population-representative	rare disease, congenital anomaly epidemiology	2019, 2023 (plaisancie2019geneticsofanophthalmia pages 2-3, harding2023realworldclinicaland pages 1-2, harding2023realworldclinicaland pages 2-3)
diagnostics: clinical	Diagnosis is clinical plus imaging/biometry, with classification into simplex, mixed, complex, and syndromic vs non-syndromic; neuroimaging is important when bilateral or developmental concerns exist	Brain MRI abnormalities in 7/28 scanned prospective MAC patients; 6/7 with intracranial findings had bilateral MAC; neuroimaging abnormalities in 14/20 in the pediatric QoL cohort, corpus callosum dysgenesis 6/20	ocular examination, axial length biometry, orbital MRI, neuroimaging, phenotype classification	2022, 2023 (harding2023realworldclinicaland pages 2-3, harding2023realworldclinicaland pages 10-11, fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)
diagnostics: molecular	Testing strategy should include gene panel/exome/genome plus CNV analysis; WGS/WES improves yield but many cases remain unsolved, especially milder/unilateral disease	>50% remain undiagnosed even after WES/WGS in review; clinic diagnostic rates ~28–34%; WGS yield 15.7% for MAC in Genomics England cohort; cES in nonisolated MAC 32.3–48.1%	gene panel, WES, WGS, chromosomal microarray, CNV analysis, HPO phenotyping	2019–2024 (plaisancie2019geneticsofanophthalmia pages 1-2, harding2023realworldclinicaland pages 8-9, jackson2020moleculardiagnosticchallenges pages 1-2, kunisetty2024highclinicalexome pages 1-2)
diagnostic yield in real-world care	Both unilateral and bilateral cases merit testing; yields are not negligible in unilateral disease and CNVs can be important	Prospective Moorfields cohort: 28% overall solved among tested families, 33% in both unilateral and bilateral cohorts; aCGH 3/3, WGS 4/17, targeted panel 3/18, single-gene 1/1	routine genetic testing, bilateral disease, unilateral disease, array CGH	2023 (harding2023realworldclinicaland pages 8-9, harding2023realworldclinicaland pages 1-1, harding2023realworldclinicaland pages 10-11)
management / real-world implementation	No disease-restoring therapy is established; management is supportive, visual rehabilitation-focused, and often includes multidisciplinary genetics/ophthalmology care and socket/prosthetic planning	Review explicitly states “currently no treatments are available” for microphthalmia; in prospective care, 66% did not require custom prostheses and 7/50 were advised customized contact shells	supportive care, low vision care, ocular prosthesis, customized contact shell, multidisciplinary care, genetic counseling	2021, 2023 (harding2021animalandcellular pages 21-22, harding2023realworldclinicaland pages 10-11)
prognosis / complications	Vision ranges from normal in fellow eye to blindness; complications depend on anatomy and associated anomalies; lifelong follow-up may be needed	In pediatric cohort, 10/35 were totally blind or had light perception; retinal detachment reported in 9% in prospective cohort and occurred from first to third decade	blindness, light perception only, retinal detachment, lifelong follow-up	2022, 2023 (harding2023realworldclinicaland pages 9-10, fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)
quality of life	Health-related quality of life is reduced in affected children/families	Parent-reported PedsQL median total score 52.4 (range 22.6–100) in ages 2–12	quality of life impairment, pediatric QoL	2022 (fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)
prevention / counseling	Primary prevention is limited because many cases are monogenic/de novo, but molecular diagnosis informs recurrence risk, prenatal options, and family counseling; environmental contributors are recognized but incompletely quantified for isolated Mendelian cases	Reviews note both genetic and environmental causes; mosaicism and incomplete penetrance materially affect recurrence-risk counseling	genetic counseling, recurrence risk, prenatal diagnosis, environmental teratogen assessment	2019–2021 (plaisancie2019geneticsofanophthalmia pages 1-2, harding2021animalandcellular pages 21-22)
model organisms	Mouse, zebrafish, Xenopus and human iPSC optic vesicles/cups are leading models; they reproduce many but not all human phenotypes	Review notes mouse, zebrafish and Xenopus as main systems; hiPSC optic cups effectively modeled VSX2-related microphthalmia; species differences limit direct translation	mouse model, zebrafish model, Xenopus model, hiPSC, optic vesicle organoid, optic cup organoid	2020–2021 (eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20, harding2021animalandcellular pages 21-22)
model-specific insights	Human iPSC models are particularly valuable for early human-specific fate defects and therapy screening, while animal models reveal conserved pathways and whole-organism effects	VSX2 null hiPSC vesicles showed WNT upregulation/RPE misexpression and pharmacologic rescue with WNT inhibition; zebrafish/CRISPR and mouse data support SOX2, PTCH1 and retinoid mechanisms	disease modeling, pathway rescue, human-specific developmental model	2016–2020 (jackson2020moleculardiagnosticchallenges pages 9-10, eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20)

Table: This compact table summarizes knowledge-base-ready findings for isolated anophthalmia-microphthalmia, including definitions, phenotypes, genes, mechanisms, diagnostics, care, prognosis, and models. It emphasizes that isolated A/M is a phenotypic category within a heterogeneous developmental eye-disorder spectrum rather than a single molecular entity.

1. Disease information

Definition and terminology

Common terms include isolated anophthalmia, isolated microphthalmia, non-syndromic anophthalmia/microphthalmia, anophthalmia–microphthalmia spectrum, and A/M. “Clinical anophthalmia” means no clinically visible eye despite possible residual tissue. MAC is broader and includes ocular coloboma; it should not be used as a synonym for isolated A/M.

Suggested ontology annotations are HP:0000528 Anophthalmia, HP:0000568 Microphthalmia, congenital onset, unilateral/bilateral involvement, and simple or complex microphthalmia. No single MONDO, OMIM, or Orphanet entry adequately represents every isolated A/M case because the phenotype spans numerous gene-specific disorders. The disease label should be linked to the relevant molecular diagnosis when known. Identifier mapping should be curated against the current MONDO/OMIM/Orphanet release rather than inferred from phenotype names. ICD coding is similarly phenotype-based and does not encode molecular subtype.

The evidence summarized here is primarily aggregated disease-level evidence from cohorts, reviews, and experimental studies—not individual EHR data. The 2023 Moorfields study is prospective real-world clinical data from 50 patients, while the 2022 pediatric study includes clinical records, examinations, neuroimaging, genetics, and parent-reported quality of life. (harding2023realworldclinicaland pages 1-1, fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)

2. Etiology

Genetic causes

Genetic disruption of early eye development is the principal established cause. More than 90–100 genes have been associated with A/M or MAC, but approximately 30 are recurrently implicated in non-syndromic families. Major classes include eye-field transcription factors, retinoid-pathway genes, BMP/TGF-β signaling genes, and regulators of optic-vesicle patterning. More than half of patients may remain molecularly undiagnosed after exome/genome sequencing, particularly those with unilateral or mild disease. (plaisancie2019geneticsofanophthalmia pages 1-2, harding2023realworldclinicaland pages 1-2)

High-confidence genes include:

SOX2: usually heterozygous loss of function/haploinsufficiency; autosomal dominant, most often de novo, with parental germline or gonosomal mosaicism documented. Deletions, nonsense, frameshift, and missense variants occur. Reviews estimate SOX2 variants in 10–15% of all A/M and 15–40% of bilateral severe A/M. Missense variants affecting DNA-binding domains may have lower penetrance and milder ocular presentations. SOX2 disease can be isolated or syndromic. (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 5-6)
OTX2: heterozygous deletions, truncating, or missense variants; autosomal dominant with approximately 40–50% de novo occurrence, marked nonpenetrance, variable expressivity, and mosaicism. Estimates range from 0.7–10% of A/M. Together, SOX2 and OTX2 may explain at least 60% of some cohorts with bilateral severe A/M. (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 6-8)
RAX: biallelic loss-of-function or damaging variants; autosomal recessive, generally bilateral and severe. It accounts for roughly 2–3% of A/M in reviews. Heterozygous carriers are usually unaffected. Neurologic features in some individuals mean that a RAX diagnosis is not automatically “isolated.” (harding2019themolecularbasis pages 15-17)
VSX2/CHX10: biallelic variants, usually causing bilateral microphthalmia, often with coloboma, cataract, glaucoma, or retinal dystrophy. The principal mechanism is defective retinal-progenitor specification and failure to suppress RPE fate. (plaisancie2019geneticsofanophthalmia pages 6-8, eintracht2020theuseof pages 8-9)
FOXE3: biallelic variants are associated with bilateral non-syndromic microphthalmia/coloboma, whereas monoallelic variants can produce anterior-segment phenotypes. (harding2023realworldclinicaland pages 9-10)
ALDH1A3: biallelic variants impair retinoic-acid synthesis. A 2023 series described nine affected people from seven families—four compound-heterozygous and three homozygous families—with bilateral A/M in every affected individual. Variants included missense, nonsense, and splice-site changes such as c.1144G>A p.(Gly382Arg), c.434C>T p.(Ala145Val), c.566G>A p.(Trp189*), and c.1233+2T>C. ALDH1A3 may explain approximately 11% of recessively inherited severe developmental eye anomalies. Neurodevelopmental findings were variably present, so isolated status must be assessed individually. (kesim2023clinicalandgenetic pages 2-3, kesim2023clinicalandgenetic pages 4-5, kesim2023clinicalandgenetic pages 1-2)
MAB21L2: both dominant and recessive disease occur. Heterozygous p.Arg51 substitutions can cause severe bilateral disease and may operate through dominant-negative effects; homozygous p.Arg247Gln produced a milder phenotype in a consanguineous family. Protein destabilization is predicted for reported missense variants. (plaisancie2019geneticsofanophthalmia pages 9-11)
Additional credible genes include PAX6, VAX1, ATOH7, SALL2, SALL4, MAF, BMP4, BMP7, GDF3, GDF6, STRA6, RARB, ABCB6, TENM3, MFRP, PRSS56, and PTCH1, although phenotype specificity and isolated-versus-syndromic presentation differ by gene and allele. (plaisancie2019geneticsofanophthalmia pages 2-3, reis2015conservedgeneticpathways pages 28-29)

Large deletions, duplications, regulatory variants, and other structural changes are also important. Chromosomal anomalies may account for up to approximately 15% of broadly ascertained MAC, although array-detectable abnormalities appear less frequent in strictly non-syndromic A/M. A 2023 prospective cohort identified deletions involving chromosomes 10, 11, and X. Regulatory variants remain underrepresented in exome-based studies, supporting WGS and CNV analysis. (harding2023realworldclinicaland pages 1-2, harding2023realworldclinicaland pages 8-9, plaisancie2019geneticsofanophthalmia pages 5-6)

Reported pathogenic variants are overwhelmingly germline, not somatic cancer mutations. Population frequencies should be compatible with rarity and inheritance—usually absent or extremely rare in gnomAD—but must be checked variant by variant. A blanket allele frequency cannot be assigned to the disease.

Environmental and infectious factors

Early pregnancy is the critical environmental window. Reviews recognize maternal infection, vitamin-A/retinoid imbalance, alcohol or teratogenic drug exposure, and other first-trimester insults as potential causes of microphthalmia. Congenital toxoplasmosis and other TORCH infections belong in the differential, especially when ocular or neurologic inflammation is present. However, quantitative causal evidence specific to isolated Mendelian A/M is limited, and no environmental exposure should be presumed causal without an appropriate maternal, fetal, and infectious evaluation. (fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3, harding2021animalandcellular pages 21-22)

Risk, protective, and gene–environment factors

Family history, parental mosaicism, consanguinity for recessive disease, and a previously affected pregnancy are major genetic risk indicators. No validated common susceptibility locus, protective allele, diet, or lifestyle intervention specifically prevents monogenic isolated A/M. Retinoic-acid biology provides biological plausibility for gene–environment interaction: variants in STRA6, ALDH1A3, or RARB perturb the same pathway influenced by vitamin-A availability and exogenous retinoids. Nevertheless, clinically actionable variant-by-exposure interaction estimates are unavailable. Avoidance of teratogenic retinoid exposure and appropriate maternal infection prevention are general pregnancy measures, not proven prevention for genetically determined A/M. (harding2019themolecularbasis pages 19-20)

3. Phenotypes

The defining findings are congenital unilateral or bilateral anophthalmia or microphthalmia. Severity ranges from a mildly short but organized globe to a tiny cystic remnant or absent globe. Involvement can be markedly asymmetric. The structural deficit itself is generally stable, but secondary ocular complications can emerge later. (plaisancie2019geneticsofanophthalmia pages 2-3, plaisancie2019geneticsofanophthalmia pages 1-2)

Associated ocular findings include coloboma, cataract, iris hypoplasia, anterior-segment dysgenesis, glaucoma, retinal dystrophy, optic-nerve abnormalities, orbital cyst, and retinal detachment. In the 2023 Moorfields cohort, 44% had non-MAC complex ocular features, cataract was the most frequent, and retinal detachment occurred in 9%, from the first through third decades. These figures come from a mixed MAC cohort and should not be interpreted as isolated-A/M-specific prevalence. (harding2023realworldclinicaland pages 9-10, harding2023realworldclinicaland pages 1-1)

Potential extraocular findings include developmental delay/intellectual disability, seizures, autism, pituitary or genital abnormalities, brain malformations, hearing loss, facial dysmorphism, and heart defects, depending on genotype. Their presence changes classification to syndromic or nonisolated disease. In a pediatric A/M cohort, only 16/35 were isolated; 19/35 had somatic, psychomotor, neuroradiologic, or genetic abnormalities. Neuroimaging was abnormal in 14/20, with corpus-callosum dysgenesis in 6/20. (fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)

Visual function depends on laterality and retained anatomy. Bilateral severe A/M may produce profound blindness; unilateral cases may have useful or normal vision in the fellow eye but remain vulnerable to amblyopia and injury. Ten of 35 children in the 2022 cohort were totally blind or had only light perception. Parent-reported PedsQL in children aged 2–12 had a median total score of 52.4 (range 22.6–100), documenting substantial quality-of-life impact. (fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)

Suggested HPO annotations include anophthalmia, microphthalmia, bilateral or unilateral involvement, ocular coloboma, cataract, glaucoma, retinal detachment, retinal dystrophy, optic-nerve hypoplasia, visual impairment/blindness, developmental delay, intellectual disability, seizures, corpus-callosum abnormality, sensorineural hearing impairment, and congenital heart defect. Phenotypes absent at the initial visit should not be encoded as definitively absent without age-appropriate examination.

4. Genetic and molecular information

The principal molecular mechanisms are:

Haploinsufficiency/dosage loss: typical of SOX2 and many OTX2 alleles.
Biallelic loss of function: typical of RAX, VSX2, ALDH1A3, and many FOXE3 presentations.
Dominant-negative protein dysfunction: proposed for specific heterozygous MAB21L2 missense substitutions.
Regulatory/CNV mechanisms: deletions or enhancer disruption can alter dosage without a coding SNV.
Pathway dysregulation: PTCH1 variants can produce overactive SHH signaling; retinoid genes alter morphogen synthesis/uptake; VSX2 loss dysregulates WNT and RPE/neural-retina fate. (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 9-11, jackson2020moleculardiagnosticchallenges pages 9-10, harding2019themolecularbasis pages 19-20)

ClinVar classifications must be assessed per variant using ACMG/AMP criteria and phenotype/inheritance concordance. The 2024 exome study reclassified variants using contemporary ACMG criteria and found a 32.3–48.1% diagnostic range in 189 people with nonisolated MAC. It proposed low-penetrance MAC expansions involving BRCA2, BRIP1, KAT6A, KAT6B, NSF, RAC1, SMARCA4, SMC1A, and TUBA1A. These findings are relevant to differential diagnosis but should not be imported uncritically into an isolated-A/M gene set because the cohort was nonisolated and many genes are pleiotropic. (kunisetty2024highclinicalexome pages 1-2)

No reproducible modifier gene or protective allele is ready for clinical annotation. Epigenetic dysregulation is biologically plausible—especially for chromatin regulators—but there is no validated A/M-specific methylation signature, histone biomarker, metabolomic profile, proteomic marker, or circulating biomarker for routine diagnosis.

5. Environmental information

Environmental causation is best considered when genetic testing is negative, maternal history is suggestive, or infection-related findings are present. Relevant history includes first-trimester medication and retinoid exposure, alcohol and substance use, severe nutritional disturbance, febrile/infectious illness, occupational/chemical exposure, diabetes and other maternal disease, and prenatal imaging. Evidence for individual environmental risk factors remains heterogeneous and often combines A/M with other congenital eye anomalies.

There is no infectious transmission, zoonotic cycle, lifestyle contagion, or postnatal environmental trigger: A/M is a prenatal developmental malformation. Infection can be causal only through maternal–fetal exposure during development.

6. Mechanism and pathophysiology

Causal chain

The upstream event is a pathogenic germline variant, CNV/regulatory alteration, or early embryonic environmental insult. This perturbs eye-field specification or signaling during the first trimester. SOX2 and OTX2 normally bind regulatory elements and activate RAX, PAX6, and SIX3; SHH separates the early eye field and patterns optic structures; BMP and retinoic-acid signals support lens placode and optic-cup morphogenesis; WNT/β-catenin favors RPE fate, while FGF and VSX2 support neural-retina specification. Failure at an early stage can abort globe formation (anophthalmia); partial failure reduces proliferation, invagination, or tissue specification, producing microphthalmia and associated coloboma or retinal/anterior-segment defects. (dash2020themastertranscription pages 3-3, eintracht2020theuseof pages 7-8, eintracht2020theuseof pages 4-7)

Retinoid mechanism: STRA6 mediates vitamin-A uptake; ALDH1A3 synthesizes retinoic acid; RARB transduces the signal. Disruption impairs ventral optic-cup and anterior-eye development. Raldh3-null mice show shortening of ventral retina, and STRA6 disruption produces microphthalmia in zebrafish. (harding2019themolecularbasis pages 19-20)

VSX2–WNT mechanism: patient-derived VSX2-null optic-vesicle models show elevated WNT11 and BMP8A, reduced FGF19, persistent MITF/RPE identity, and defective neural-retina/RPE boundary specification. WNT inhibition rescued aspects of the model phenotype, establishing pathway causality in vitro but not yet a prenatal or postnatal human therapy. (eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20)

SHH mechanism: PTCH1 inhibits SHH signaling. Patient variants tested in zebrafish altered SHH signaling, and SOX2 was shown to bind and regulate PTCH1. The authors estimated PTCH1 variants could contribute to as much as 10% of broadly defined ocular developmental anomalies and proposed overactive SHH as a mechanism. This estimate is not specific to isolated A/M. (reis2015conservedgeneticpathways pages 28-29)

Post-transcriptional SOX2 regulation: RBM24 binds AU-rich elements in the SOX2 3′ UTR and stabilizes its mRNA. Rbm24 loss in mouse or zebrafish reduces Sox2 and produces anophthalmia/microphthalmia with ocular apoptosis and reduced Lhx2, Pax6, Jag1, E-cadherin, and crystallin expression. This is experimental model evidence, not yet a routinely recognized human A/M subtype. (dash2020themastertranscription pages 3-3)

Suggested GO concepts include eye-field specification, camera-type eye development, optic-vesicle morphogenesis, optic-cup morphogenesis, retina development, retinal-progenitor-cell proliferation, cell-fate specification, canonical WNT signaling, BMP signaling, SHH signaling, retinoic-acid biosynthesis/signaling, transcriptional regulation, and apoptosis. Suggested cell types are retinal progenitor cell, neuroepithelial cell, retinal pigment epithelial cell, lens epithelial cell, neural-crest-derived periocular mesenchymal cell, retinal neuron, and Müller glial cell.

There is no established primary inflammatory, autoimmune, fibrotic, mitochondrial, lysosomal, or metabolic-storage mechanism. Immune involvement is relevant chiefly to congenital infection, not inherited isolated A/M.

7. Anatomical structures affected

The primary organ is the eye and orbit. Developmentally implicated structures include the eye field, optic sulcus/vesicle, optic cup, neural retina, RPE, lens placode/lens, ciliary margin, optic nerve, and periocular mesenchyme. Severe loss of globe volume also affects postnatal orbital and facial growth.

Suggested UBERON concepts include eye, eyeball, orbit, optic vesicle, optic cup, neural retina, retinal pigment epithelium, lens, cornea, iris, ciliary body, optic nerve, and periocular mesenchyme. Relevant GO cellular compartments depend on gene product: SOX2, OTX2, RAX, VSX2, and FOXE3 act principally in the nucleus/chromatin; STRA6 is a plasma-membrane receptor/transporter; ALDH1A3 is a cytosolic enzyme; PTCH1 is a membrane protein.

Lateralization may be unilateral, bilateral, or asymmetric. Severe bilateral disease is more often molecularly diagnosed, but recent real-world data demonstrate meaningful yield in unilateral cases as well. (harding2023realworldclinicaland pages 1-1, harding2023realworldclinicaland pages 10-11)

8. Temporal development

A/M is congenital, with the causal developmental disturbance occurring during early embryonic eye formation. The structural deficit is permanent and is not a relapsing or remitting disorder. The visual and cosmetic consequences are lifelong.

Secondary manifestations can evolve: refractive error or amblyopia may become apparent in childhood; glaucoma, retinal dystrophy, or retinal detachment can develop later; orbital and facial asymmetry can become more apparent with growth. Retinal detachment occurred from the first to third decade in the prospective MAC series. (harding2023realworldclinicaland pages 9-10)

Critical windows are prenatal eye-field and optic-vesicle/cup development for causation, infancy/early childhood for orbital expansion and amblyopia management, and lifelong surveillance for complications. There is no spontaneous anatomical remission.

9. Inheritance and population

Inheritance may be autosomal dominant, autosomal recessive, X-linked in selected syndromic genes such as BCOR, or sporadic through de novo mutation/CNV. Dominant SOX2/OTX2 disease often shows incomplete penetrance, variable expressivity, and parental mosaicism. Recessive ALDH1A3, RAX, VSX2, and FOXE3 disease is enriched in consanguineous families, but compound heterozygosity occurs in nonconsanguineous families. (harding2019themolecularbasis pages 15-17, plaisancie2019geneticsofanophthalmia pages 6-8, kesim2023clinicalandgenetic pages 1-2)

No genetic anticipation is established. Germline/gonosomal mosaicism is clinically important because recurrence risk after an apparently de novo diagnosis is not zero. Founder variants may occur locally, but no universal founder effect or carrier frequency exists across this heterogeneous group. Carrier frequency must be calculated for the family’s gene and population.

No robust sex predilection is established. The 2023 clinic cohort was 60% female, but it was small and referral-based and should not be interpreted as a population sex ratio. (harding2023realworldclinicaland pages 2-3)

10. Diagnostics

Clinical and imaging work-up

Diagnosis begins with comprehensive pediatric ophthalmologic examination: inspection for globe tissue, corneal diameter, axial length by ultrasound/biometry, anterior- and posterior-segment examination where possible, refraction, intraocular pressure, visual behavior/acuity, and evaluation of the fellow eye. Orbital ultrasound or MRI distinguishes absent globe, extreme microphthalmia, cyst, and other orbital lesions. Electrodiagnostic testing may characterize residual retinal function. (plaisancie2019geneticsofanophthalmia pages 2-3, harding2023realworldclinicaland pages 2-3)

Systemic assessment should include growth and development, neurologic examination, hearing, endocrine/genital assessment where SOX2/OTX2 is suspected, cardiac and renal examination as indicated, and dysmorphology/genetics review. Brain/orbital MRI is particularly appropriate for bilateral severe disease, developmental delay, seizures, optic-nerve abnormality, or suspected midline/pituitary involvement. In the 2023 cohort, 7/28 scanned patients had intracranial abnormalities, six of whom had bilateral MAC. (harding2023realworldclinicaland pages 10-11)

Prenatal ultrasound can detect absent or very small globes, and fetal MRI can clarify anatomy. A molecular diagnosis in a family permits targeted prenatal diagnosis or preimplantation genetic testing.

Molecular testing strategy

A practical sequence is:

Chromosomal microarray/CNV analysis, especially with bilateral severe disease, dysmorphism, developmental findings, or multiple anomalies.
Comprehensive developmental-eye-disorder panel including dominant, recessive, and CNV-capable analysis.
Trio exome or genome sequencing if panel/CMA is nondiagnostic; WGS is preferred when regulatory, deep-intronic, structural, or complex variants are suspected.
Reanalysis as gene–disease knowledge improves and careful HPO terms are added.
Parental testing for phase, de novo status, and mosaicism.

Karyotyping or FISH is reserved for a suspected cytogenetic rearrangement; mitochondrial or repeat-expansion testing is not routine. RNA studies may help resolve splice variants but are not standard first-line diagnostics. (plaisancie2019geneticsofanophthalmia pages 5-6, jackson2020moleculardiagnosticchallenges pages 1-2, jackson2020moleculardiagnosticchallenges pages 9-10)

Real-world yields vary by cohort. In the 2023 Moorfields study, 11/39 families were solved (28%); non-syndromic cases had a 28% yield (8/29), and unilateral and bilateral groups each had a reported 33% rate. WGS solved 4/17, targeted panels 3/18, and aCGH 3/3, although the method-specific samples were too small for comparative effectiveness claims. (harding2023realworldclinicaland pages 8-9, harding2023realworldclinicaland pages 1-1)

In Genomics England, WGS yielded 15.7% for MAC. In contrast, 2024 clinical-exome analysis of 189 nonisolated MAC patients produced a 32.3–48.1% range, reflecting different definitions of a causal result. These data support sequencing but also demonstrate that diagnostic yield depends strongly on phenotype and interpretation. (jackson2020moleculardiagnosticchallenges pages 1-2, kunisetty2024highclinicalexome pages 1-2)

Differential diagnosis

Important differentials include extreme microphthalmia versus true anophthalmia; microphthalmia with orbital cyst; isolated coloboma; cryptophthalmos/Fraser syndrome; congenital cystic eye; anterior-segment dysgenesis; nanophthalmos; congenital cataract obscuring a globe; retinopathy of prematurity or acquired phthisis; TORCH-related ocular destruction; and syndromic A/M such as SOX2 disorder, OTX2-related pituitary disease, STRA6-related Matthew-Wood syndrome, CHARGE, Lenz microphthalmia, and BCOR-related disease.

There are no serum, urine, biopsy, liquid-biopsy, proteomic, or metabolomic biomarkers diagnostic of isolated A/M. Histopathology is not required clinically.

11. Outcome and prognosis

Life expectancy is generally expected to be normal in genuinely isolated disease; mortality is driven by associated systemic malformations rather than the ocular anomaly itself. No validated 5- or 10-year survival statistics exist for isolated A/M.

Vision depends principally on bilaterality, residual retinal/optic-nerve development, coloboma, and fellow-eye status. Severe bilateral anophthalmia causes lifelong blindness; unilateral disease may preserve functional independence with protection and optimization of the fellow eye. The malformed globe does not recover anatomically. Secondary glaucoma, cataract, retinal dystrophy/detachment, amblyopia, socket contraction, prosthesis problems, and facial asymmetry contribute to morbidity. (harding2023realworldclinicaland pages 9-10, fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3)

Useful prognostic variables are laterality, axial length, residual retinal function, optic-nerve and brain imaging, associated ocular defects, developmental status, and molecular diagnosis. There is no validated prognostic molecular biomarker beyond genotype–phenotype correlations.

12. Treatment and current implementation

There is no approved pharmacologic, gene, RNA, cell, or immune therapy that reconstructs an absent or severely malformed eye. The 2021 model review states directly that “currently no treatments are available,” referring to disease-restoring treatment for microphthalmia. Management is therefore supportive, rehabilitative, cosmetic, and complication-directed. (harding2021animalandcellular pages 21-22)

Key interventions include:

Early low-vision and developmental services; orientation/mobility training for bilateral visual loss.
Refraction, amblyopia treatment, and treatment of cataract, glaucoma, retinal detachment, or other remediable pathology.
Polycarbonate protection for a functional fellow eye.
Serial socket conformers, customized contact shells, or prosthetic eyes to support orbital symmetry and cosmesis; selected severe sockets may require expandable implants or reconstructive surgery.
Psychosocial support and school accommodations.
Multidisciplinary ophthalmology, oculoplastics, ocularist, clinical genetics, pediatrics, neurology/endocrinology, and rehabilitation care according to genotype and findings.

In the Moorfields real-world cohort, 66% did not need customized prostheses, while 7/50 were advised customized contact shells because of small eye size. These figures illustrate individualized care rather than a universal treatment algorithm. (harding2023realworldclinicaland pages 10-11)

Suggested NCIT intervention concepts include genetic counseling, ophthalmologic examination, magnetic resonance imaging, ocular ultrasound, low-vision rehabilitation, ocular prosthesis, reconstructive surgery, cataract surgery, glaucoma treatment, and retinal-detachment repair. No A/M-specific pharmacogenomic guidance exists.

The clinical-trial search found socket/prosthetic or imaging studies but no active disease-modifying trial specifically restoring congenital isolated A/M. Experimental WNT rescue in VSX2-mutant optic vesicles is a mechanistic proof of concept, not a human treatment. (eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20)

13. Prevention

Primary prevention is limited for monogenic or de novo disease. General measures include avoiding known teratogenic retinoids, optimizing maternal health and nutrition without excessive vitamin A, preventing and treating maternal infections, and reviewing medications before pregnancy. There is no A/M-specific vaccine or prophylactic drug.

Secondary prevention consists of prenatal imaging in high-risk pregnancies, targeted prenatal testing when a familial variant is known, newborn eye examination, prompt molecular diagnosis, and early screening for syndromic manifestations. Population newborn biochemical screening is not applicable.

Tertiary prevention includes early orbital/socket management, amblyopia prevention, protection of the fellow eye, surveillance for glaucoma and retinal detachment, low-vision rehabilitation, and developmental/educational support.

Genetic counseling should explain gene-specific inheritance, incomplete penetrance, variable expressivity, and mosaicism. Reproductive options include natural conception with targeted prenatal diagnosis, IVF with preimplantation genetic testing for a known familial variant, donor gametes, and adoption. Recurrence risk cannot be assigned from the phenotype alone.

14. Other species and natural disease

Congenital microphthalmia/anophthalmia occurs naturally in domestic and laboratory animals, but this review retrieved stronger experimental than veterinary natural-history evidence. Species relevant to comparative biology include Mus musculus (NCBI Taxon 10090), Danio rerio (7955), and Xenopus species, with conserved orthologs of SOX2, OTX2, RAX, VSX2, ALDH1A3, PTCH1, and BMP-pathway genes. No zoonotic transmission is possible because this is a developmental phenotype, not an infectious disease.

Breed-specific VBO annotations, veterinary prevalence, and natural founder variants require separate OMIA/VBO curation; they are not established by the retrieved evidence.

15. Model organisms and advanced technologies

Mouse, zebrafish, Xenopus, and chick models have defined conserved eye-field, retinoid, BMP, WNT, and SHH pathways. Knockout, knockdown, CRISPR, and dosage-sensitive models of Sox2, Otx2, Rax, Vsx2, Raldh3/Aldh1a3, Stra6, Ptch1, Bmp7, and Rbm24 reproduce anophthalmia, microphthalmia, retinal-patterning defects, or related ocular phenotypes. (harding2019themolecularbasis pages 19-20, harding2021animalandcellular pages 21-22, reis2015conservedgeneticpathways pages 28-29)

Species differences are important. For example, zebrafish double loss of vsx genes can preserve neural-retina specification despite severe bipolar-cell depletion, whereas mammalian VSX2 loss produces microphthalmia. Corneal timing, neural-crest migration, retinal regeneration, and gene redundancy differ across organisms, limiting direct extrapolation. (harding2019themolecularbasis pages 19-20)

Patient-derived hiPSC optic vesicles/cups are the most clinically relevant emerging platform. They recapitulate human fetal developmental transcriptional programs and can model patient-specific defects. VSX2-null vesicles demonstrated WNT upregulation and RPE mis-specification, with partial pathway rescue by WNT inhibition. Such organoids lack complete vasculature, immune interactions, and whole-orbit biomechanics, but they provide a platform for functional variant analysis and drug screening. (eintracht2020theuseof pages 8-9, eintracht2020theuseof pages 4-7)

Single-cell transcriptomics and spatial methods are promising for mapping human eye-development cell states, but no validated isolated-A/M single-cell, spatial, proteomic, metabolomic, or multi-omic clinical signature is currently available. The main immediate application is mechanistic research rather than diagnosis.

Recent developments and expert interpretation

2023 real-world management: Harding et al., published October 2023, prospectively studied 50 MAC patients and found 44% complex ocular disease, 34% systemic involvement, and a 28% family-level molecular yield. Their conclusion supports routine testing in unilateral as well as bilateral cases. DOI: https://doi.org/10.1136/bjo-2022-321991. (harding2023realworldclinicaland pages 1-1)
2023 ALDH1A3 expansion: Kesim et al., published March 2023, reported seven families with biallelic variants. The abstract states: “All affected individuals had bilateral anophthalmia/microphthalmia,” while neurodevelopmental features showed marked variability. DOI: https://doi.org/10.1038/s41431-023-01342-8. (kesim2023clinicalandgenetic pages 1-2)
2024 clinical exomes: Kunisetty et al., published March 19, 2024, found cES efficacy of 32.3–48.1% in 189 nonisolated MAC cases and emphasized that many implicated genes were absent from commercial ophthalmic panels. DOI: https://doi.org/10.1167/iovs.65.3.25. This result supports broad exome/genome testing but does not directly define isolated A/M yield. (kunisetty2024highclinicalexome pages 1-2)
Human developmental models: Patient-derived optic-vesicle studies show that developmental pathway defects can be modeled and pharmacologically modulated in vitro. Experts regard these systems as valuable for discovering targets, but prenatal timing and irreversible structural loss make postnatal translation especially challenging. (eintracht2020theuseof pages 8-9, harding2019themolecularbasis pages 19-20)

Evidence limitations

Published cohorts frequently combine anophthalmia, microphthalmia, and coloboma and mix isolated with syndromic disease. Consequently, many frequencies in this report are MAC-wide and are explicitly labeled as such. Gene-specific penetrance, carrier frequency, environmental effect sizes, treatment-response rates, survival statistics, and population-stratified prevalence are generally unavailable. Exact PMIDs were not present in the retrieved full-text metadata; DOI URLs and publication dates are therefore supplied rather than risking incorrect PMID assignment.

References

(plaisancie2019geneticsofanophthalmia pages 2-3): Julie Plaisancié, Fabiola Ceroni, R. Holt, C. Z. Seco, P. Calvas, N. Chassaing, and N. Ragge. Genetics of anophthalmia and microphthalmia. part 1: non-syndromic anophthalmia/microphthalmia. Human Genetics, 138:799-830, Feb 2019. URL: https://doi.org/10.1007/s00439-019-01977-y, doi:10.1007/s00439-019-01977-y. This article has 136 citations and is from a peer-reviewed journal.
(plaisancie2019geneticsofanophthalmia pages 1-2): Julie Plaisancié, Fabiola Ceroni, R. Holt, C. Z. Seco, P. Calvas, N. Chassaing, and N. Ragge. Genetics of anophthalmia and microphthalmia. part 1: non-syndromic anophthalmia/microphthalmia. Human Genetics, 138:799-830, Feb 2019. URL: https://doi.org/10.1007/s00439-019-01977-y, doi:10.1007/s00439-019-01977-y. This article has 136 citations and is from a peer-reviewed journal.
(harding2023realworldclinicaland pages 2-3): Philippa Harding, Sri Gore, Samantha Malka, Jayashree Rajkumar, Ngozi Oluonye, and Mariya Moosajee. Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma. The British Journal of Ophthalmology, 107:1925-1935, Oct 2023. URL: https://doi.org/10.1136/bjo-2022-321991, doi:10.1136/bjo-2022-321991. This article has 27 citations.
(harding2023realworldclinicaland pages 1-2): Philippa Harding, Sri Gore, Samantha Malka, Jayashree Rajkumar, Ngozi Oluonye, and Mariya Moosajee. Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma. The British Journal of Ophthalmology, 107:1925-1935, Oct 2023. URL: https://doi.org/10.1136/bjo-2022-321991, doi:10.1136/bjo-2022-321991. This article has 27 citations.
(harding2023realworldclinicaland pages 9-10): Philippa Harding, Sri Gore, Samantha Malka, Jayashree Rajkumar, Ngozi Oluonye, and Mariya Moosajee. Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma. The British Journal of Ophthalmology, 107:1925-1935, Oct 2023. URL: https://doi.org/10.1136/bjo-2022-321991, doi:10.1136/bjo-2022-321991. This article has 27 citations.
(harding2023realworldclinicaland pages 8-9): Philippa Harding, Sri Gore, Samantha Malka, Jayashree Rajkumar, Ngozi Oluonye, and Mariya Moosajee. Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma. The British Journal of Ophthalmology, 107:1925-1935, Oct 2023. URL: https://doi.org/10.1136/bjo-2022-321991, doi:10.1136/bjo-2022-321991. This article has 27 citations.
(plaisancie2019geneticsofanophthalmia pages 6-8): Julie Plaisancié, Fabiola Ceroni, R. Holt, C. Z. Seco, P. Calvas, N. Chassaing, and N. Ragge. Genetics of anophthalmia and microphthalmia. part 1: non-syndromic anophthalmia/microphthalmia. Human Genetics, 138:799-830, Feb 2019. URL: https://doi.org/10.1007/s00439-019-01977-y, doi:10.1007/s00439-019-01977-y. This article has 136 citations and is from a peer-reviewed journal.
(fahnehjelm2022anophthalmiaandmicrophthalmia pages 1-3): Cecilia Fahnehjelm, Eva Dafgård Kopp, Josephine Wincent, Evin Güven, Mattias Nilsson, Monica Olsson, and Kristina Teär Fahnehjelm. Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life. Ophthalmic Genetics, 43:172-183, Feb 2022. URL: https://doi.org/10.1080/13816810.2021.1989600, doi:10.1080/13816810.2021.1989600. This article has 21 citations and is from a peer-reviewed journal.
(harding2019themolecularbasis pages 15-17): Philippa Harding and Mariya Moosajee. The molecular basis of human anophthalmia and microphthalmia. Journal of Developmental Biology, 7:16, Aug 2019. URL: https://doi.org/10.3390/jdb7030016, doi:10.3390/jdb7030016. This article has 103 citations.
(plaisancie2019geneticsofanophthalmia pages 5-6): Julie Plaisancié, Fabiola Ceroni, R. Holt, C. Z. Seco, P. Calvas, N. Chassaing, and N. Ragge. Genetics of anophthalmia and microphthalmia. part 1: non-syndromic anophthalmia/microphthalmia. Human Genetics, 138:799-830, Feb 2019. URL: https://doi.org/10.1007/s00439-019-01977-y, doi:10.1007/s00439-019-01977-y. This article has 136 citations and is from a peer-reviewed journal.
(plaisancie2019geneticsofanophthalmia pages 9-11): Julie Plaisancié, Fabiola Ceroni, R. Holt, C. Z. Seco, P. Calvas, N. Chassaing, and N. Ragge. Genetics of anophthalmia and microphthalmia. part 1: non-syndromic anophthalmia/microphthalmia. Human Genetics, 138:799-830, Feb 2019. URL: https://doi.org/10.1007/s00439-019-01977-y, doi:10.1007/s00439-019-01977-y. This article has 136 citations and is from a peer-reviewed journal.
(kesim2023clinicalandgenetic pages 1-2): Yesim Kesim, Fabiola Ceroni, Alejandra Damián, Fiona Blanco-Kelly, Carmen Ayuso, Kathy Williamson, Véronique Paquis-Flucklinger, Dorine A Bax, Julie Plaisancié, Claudine Rieubland, Mostafa Chamlal, Marta Cortón, Nicolas Chassaing, Patrick Calvas, and Nicola K Ragge. Clinical and genetic analysis further delineates the phenotypic spectrum of aldh1a3-related anophthalmia and microphthalmia. European Journal of Human Genetics, 31:1175-1180, Mar 2023. URL: https://doi.org/10.1038/s41431-023-01342-8, doi:10.1038/s41431-023-01342-8. This article has 7 citations and is from a domain leading peer-reviewed journal.
(dash2020themastertranscription pages 3-3): Soma Dash, Lindy K Brastrom, Shaili D Patel, C Anthony Scott, Diane C Slusarski, and Salil A Lachke. The master transcription factor sox2, mutated in anophthalmia/microphthalmia, is post-transcriptionally regulated by the conserved rna-binding protein rbm24 in vertebrate eye development. Human Molecular Genetics, 29(4):591-604, Dec 2020. URL: https://doi.org/10.1093/hmg/ddz278, doi:10.1093/hmg/ddz278. This article has 54 citations and is from a domain leading peer-reviewed journal.
(eintracht2020theuseof pages 7-8): Jonathan Eintracht, Maria Toms, and Mariya Moosajee. The use of induced pluripotent stem cells as a model for developmental eye disorders. Frontiers in Cellular Neuroscience, Aug 2020. URL: https://doi.org/10.3389/fncel.2020.00265, doi:10.3389/fncel.2020.00265. This article has 28 citations.
(reis2015conservedgeneticpathways pages 28-29): Linda M. Reis and Elena V. Semina. Conserved genetic pathways associated with microphthalmia, anophthalmia, and coloboma. Birth defects research. Part C, Embryo today : reviews, 105 2:96-113, Jun 2015. URL: https://doi.org/10.1002/bdrc.21097, doi:10.1002/bdrc.21097. This article has 91 citations.
(jackson2020moleculardiagnosticchallenges pages 9-10): Daniel Jackson, Samantha Malka, Philippa Harding, Juliana Palma, Hannah Dunbar, and Mariya Moosajee. Molecular diagnostic challenges for non‐retinal developmental eye disorders in the united kingdom. American Journal of Medical Genetics. Part C, Seminars in Medical Genetics, 184:578-589, Aug 2020. URL: https://doi.org/10.1002/ajmg.c.31837, doi:10.1002/ajmg.c.31837. This article has 55 citations.
(eintracht2020theuseof pages 8-9): Jonathan Eintracht, Maria Toms, and Mariya Moosajee. The use of induced pluripotent stem cells as a model for developmental eye disorders. Frontiers in Cellular Neuroscience, Aug 2020. URL: https://doi.org/10.3389/fncel.2020.00265, doi:10.3389/fncel.2020.00265. This article has 28 citations.
(harding2019themolecularbasis pages 19-20): Philippa Harding and Mariya Moosajee. The molecular basis of human anophthalmia and microphthalmia. Journal of Developmental Biology, 7:16, Aug 2019. URL: https://doi.org/10.3390/jdb7030016, doi:10.3390/jdb7030016. This article has 103 citations.
(harding2023realworldclinicaland pages 10-11): Philippa Harding, Sri Gore, Samantha Malka, Jayashree Rajkumar, Ngozi Oluonye, and Mariya Moosajee. Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma. The British Journal of Ophthalmology, 107:1925-1935, Oct 2023. URL: https://doi.org/10.1136/bjo-2022-321991, doi:10.1136/bjo-2022-321991. This article has 27 citations.
(jackson2020moleculardiagnosticchallenges pages 1-2): Daniel Jackson, Samantha Malka, Philippa Harding, Juliana Palma, Hannah Dunbar, and Mariya Moosajee. Molecular diagnostic challenges for non‐retinal developmental eye disorders in the united kingdom. American Journal of Medical Genetics. Part C, Seminars in Medical Genetics, 184:578-589, Aug 2020. URL: https://doi.org/10.1002/ajmg.c.31837, doi:10.1002/ajmg.c.31837. This article has 55 citations.
(kunisetty2024highclinicalexome pages 1-2): Bhavana Kunisetty, Bailey A. Martin-Giacalone, Xiaonan Zhao, Pamela N. Luna, Brian P. Brooks, Robert B. Hufnagel, Chad A. Shaw, Jill A. Rosenfeld, A. J. Agopian, Philip J. Lupo, and Daryl A. Scott. High clinical exome sequencing diagnostic rates and novel phenotypic expansions for nonisolated microphthalmia, anophthalmia, and coloboma. Investigative Opthalmology & Visual Science, 65:25, Mar 2024. URL: https://doi.org/10.1167/iovs.65.3.25, doi:10.1167/iovs.65.3.25. This article has 8 citations.
(harding2023realworldclinicaland pages 1-1): Philippa Harding, Sri Gore, Samantha Malka, Jayashree Rajkumar, Ngozi Oluonye, and Mariya Moosajee. Real-world clinical and molecular management of 50 prospective patients with microphthalmia, anophthalmia and/or ocular coloboma. The British Journal of Ophthalmology, 107:1925-1935, Oct 2023. URL: https://doi.org/10.1136/bjo-2022-321991, doi:10.1136/bjo-2022-321991. This article has 27 citations.
(harding2021animalandcellular pages 21-22): Philippa Harding, Dulce Lima Cunha, and Mariya Moosajee. Animal and cellular models of microphthalmia. Therapeutic Advances in Rare Disease, Jan 2021. URL: https://doi.org/10.1177/2633004021997447, doi:10.1177/2633004021997447. This article has 15 citations.
(kesim2023clinicalandgenetic pages 2-3): Yesim Kesim, Fabiola Ceroni, Alejandra Damián, Fiona Blanco-Kelly, Carmen Ayuso, Kathy Williamson, Véronique Paquis-Flucklinger, Dorine A Bax, Julie Plaisancié, Claudine Rieubland, Mostafa Chamlal, Marta Cortón, Nicolas Chassaing, Patrick Calvas, and Nicola K Ragge. Clinical and genetic analysis further delineates the phenotypic spectrum of aldh1a3-related anophthalmia and microphthalmia. European Journal of Human Genetics, 31:1175-1180, Mar 2023. URL: https://doi.org/10.1038/s41431-023-01342-8, doi:10.1038/s41431-023-01342-8. This article has 7 citations and is from a domain leading peer-reviewed journal.
(kesim2023clinicalandgenetic pages 4-5): Yesim Kesim, Fabiola Ceroni, Alejandra Damián, Fiona Blanco-Kelly, Carmen Ayuso, Kathy Williamson, Véronique Paquis-Flucklinger, Dorine A Bax, Julie Plaisancié, Claudine Rieubland, Mostafa Chamlal, Marta Cortón, Nicolas Chassaing, Patrick Calvas, and Nicola K Ragge. Clinical and genetic analysis further delineates the phenotypic spectrum of aldh1a3-related anophthalmia and microphthalmia. European Journal of Human Genetics, 31:1175-1180, Mar 2023. URL: https://doi.org/10.1038/s41431-023-01342-8, doi:10.1038/s41431-023-01342-8. This article has 7 citations and is from a domain leading peer-reviewed journal.
(eintracht2020theuseof pages 4-7): Jonathan Eintracht, Maria Toms, and Mariya Moosajee. The use of induced pluripotent stem cells as a model for developmental eye disorders. Frontiers in Cellular Neuroscience, Aug 2020. URL: https://doi.org/10.3389/fncel.2020.00265, doi:10.3389/fncel.2020.00265. This article has 28 citations.

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Executive summary and scope

1. Disease information

Definition and terminology

2. Etiology

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Environmental and infectious factors

Risk, protective, and gene–environment factors

3. Phenotypes

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