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)

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:

1. Haploinsufficiency/dosage loss: typical of SOX2 and many OTX2 alleles.
2. Biallelic loss of function: typical of RAX, VSX2, ALDH1A3, and many FOXE3 presentations.
3. Dominant-negative protein dysfunction: proposed for specific heterozygous MAB21L2 missense substitutions.
4. Regulatory/CNV mechanisms: deletions or enhancer disruption can alter dosage without a coding SNV.
5. 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:

1. Chromosomal microarray/CNV analysis, especially with bilateral severe disease, dysmorphism, developmental findings, or multiple anomalies.
2. Comprehensive developmental-eye-disorder panel including dominant, recessive, and CNV-capable analysis.
3. Trio exome or genome sequencing if panel/CMA is nondiagnostic; WGS is preferred when regulatory, deep-intronic, structural, or complex variants are suspected.
4. Reanalysis as gene–disease knowledge improves and careful HPO terms are added.
5. 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

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