Importance:Inherited retinal dystrophies are a group of disorders that may lead to progressive vision loss. Improved knowledge of their molecular genetics is important for accurate diagnosis or development of targeted therapies. Objective:To identify pathogenic variants in the SLC6A6 gene (encoding TauT, the main transporter for taurine) and assess their role in the molecular pathogenesis of hereditary early-onset retinal dystrophy (EORD) in affected individuals from diverse ethnic backgrounds. Design, Setting, and Participants:This was a retrospective, multicenter observational study conducted between June 2019 and March 2025, involving 7 affected and 10 unaffected individuals from 4 unrelated families recruited in Pakistan, Italy, the US, and France. Exposure:Pathogenic variants in SLC6A6 in individuals with EORD. Main Outcomes and Measures:Genetic, clinical, and functional outcomes of pathogenic variants in SLC6A6 in individuals with Leber congenital amaurosis (LCA) and EORD. All patients underwent standard clinical examinations, including visual acuity, full-field electroretinography, and multimodal retinal imaging, followed by measurement of fasting plasma taurine levels. In vitro and ex vivo taurine transport and membrane trafficking assays in human embryonic kidney (HEK)-293 cells, as well as patient-derived fibroblasts, were also performed. Results:All 7 affected individuals exhibited LCA/EORD, with extraocular findings in some. Genetic analysis identified homozygous pathogenic SLC6A6 variants in all affected individuals, while unaffected relatives were heterozygous carriers. Families 1 and 2 carried missense variants p.(Thr249Ile) and p.(Ala294Thr), while families 3 and 4 carried truncating variants-a deletion of exon 11 and p.(Thr113Ter), respectively. Functional studies demonstrated that both missense variants are associated with complete loss of taurine transport in HEK-293 cells and patient-derived fibroblasts. Additionally, irrespective of the variants considered, plasma taurine levels in affected individuals were reduced compared with heterozygous carriers (difference between means, -31.7 µmol/L; 95% CI, -42.7 to -20.8; P < .001) and healthy control individuals (difference between means, -37.7 µmol/L; 95% CI -41.6 to -33.8; P < .001). Conclusions and Relevance:These findings confirm and expand the role of biallelic variants in SLC6A6 in association with LCA/EORD due to impaired taurine transport. These findings suggest that patients with a diagnosis of SLC6A6-related LCA/EORD may be candidates for investigational oral taurine supplementation.

Oculocutaneous albinism (OCA) is a genetic condition associated with impaired visual acuity and increased skin cancer risk. When OCA is due to defects in melanosome ion transport, abnormally acidic conditions in the melanosome lumen inhibit tyrosinase, the critical pigment synthetic enzyme. Hence, a therapeutic approach that optimizes melanosome pH to increase pigment production presents a potential treatment for OCA and a method for decreasing skin cancer risk. Here, we report that reduction in sAC ( ADCY10 ) activity via naturally occurring human variants in ADCY10 restores OCA pigmentation, and sAC inhibition increases melanin synthesis in both human and mouse OCA models. These findings demonstrate that targeting melanosome pH is an effective, previously untapped therapeutic strategy for OCA and elevated skin cancer risk.

Ciliopathies comprise a spectrum of disorders involving mutations in over 150 genes affecting the primary cilium, with retinal degeneration as a prominent feature driven by concomitant developmental and maturation defects in photoreceptors and the retinal pigment epithelium (RPE). Current single-gene-targeted therapeutic approaches are expensive with limited scalability. We hypothesize that downstream of primary cilium dysfunction, mutation-agnostic shared pathways initiate tissue defects. To test this hypothesis, we here develop induced pluripotent stem cell-derived RPE models (iRPE) from nine (BBS1, BBS10, BBS16, CEP290, LCA5, MYO7A, PRPF31) patients with ciliopathy with severe retinal degeneration. Despite heterogeneity in disease severity, consistent with underlying ciliary structural defects, all ciliopathy iRPE exhibit abnormal epithelial polarization and impaired mitochondrial health initiated by dysregulated TGF-β signaling-driven mesenchymal drift. Addressing these gene-agnostic disease phenotypes, our study identifies two drugs, pioglitazone, a mitochondrial metabolic modulator, and galunisertib, a TGFBR1 inhibitor, as potential therapeutic candidates for multiple ciliopathy subtypes.

Optic fissure (OF) is a transient structure in the ventral optic cup, which acts as a conduit for periocular mesenchyme cells to enter the eye, forming hyaloid vasculature and retinal ganglion axons to exit. Optic fissure closes to form a continuous layer of retinal pigment epithelium and neural retina. Failure of OF closure results in coloboma, which is mostly genetic in nature. The severity of blindness depends on the tissue it effects and accounts for 10% of childhood blindness. In the current study, we describe coloboma pathogenesis caused by hippo effectors yap1 and wwtr1. Both the paralogs are expressed in the OF edges, possibly in the pioneer cells. wwtr1 homozygotes do not have coloboma, while yap1 homozygotes have coloboma and pigment defects which are exacerbated by absence of one copy of wwtr1 (yap1 -/- ; wwtr1 +/- ). The coloboma observed in these mutants is not due to defective optic cup morphogenesis nor an overgrown optic nerve. The pigment defects are more pronounced at the OF with complete absence of RPE specific transcription factors mitfA, tfec, and pigmentation gene dct. On the other hand, NR specific genes are upregulated and the unpigmented region at the OF have transdifferentiated retinal ganglion cells, amacrine, and photoreceptor cells. Our observations indicate that in the absence of yap1 and wwtr1, the cells at the OF cannot attain a conducive state to fuse nor they maintain the RPE specific fate and instead they transdifferentiate into unpigmented retina, causing a steric block for fusion, resulting in coloboma.

Significant loss of pigmentation can increase visual disability, skin cancer risk, and psychosocial stress. Tyrosinase (TYR) catalyzes the first and rate-limiting step of melanin synthesis. Inhibitors of TYR are well established and are currently used in clinical settings; however, there is a dearth of direct activators of TYR. Here, using a human TYR construct, we developed high-throughput screening methods, in cell confirmatory assays employing 13 C-tyrosine tracing, and computational analysis techniques, and identified ampyrone (4-aminoantipyrine) as a TYR activator. Ampyrone increased the in vitro catalytic activity of the human recombinant intramelanosomal domain of TYR (hTYR) and its hypomorphic variant, Pro406Leu (P406L), a cause of oculocutaneous albinism type 1B (OCA1B). Moreover, ampyrone induced melanin synthesis in both WT and OCA1B human melanocytes, mouse OCA2 melanocytes, as well as 3-dimensional (3D) human skin cultures. Computational studies provided additional insight into the effects of direct TYR agonists on enzyme activity. Our results identify ampyrone as a lead candidate for TYR activation, potentially supporting the development of therapies for patients with genetic and acquired diseases of hypopigmentation.

Abstract Background Low-vision rehabilitative support for children with multiple-disability conditions is underexplored. We conduct a pilot study of an assistive device in children with CLN3 disease, a multisystemic pediatric blindness and neurodegenerative condition. The prospective, pilot study (NCT04974307) evaluated the safety, feasibility and preliminary efficacy of the OrCam MyEye 2 in aiding daily living tasks. We used multimodal assessments of feasibility and efficacy to assess nine participants with CLN3 disease and one with non-CLN3 low vision (age 8.1-17.4 years; females:males 2:8) at baseline (Day 1, without the device) and Day 5 (with the device). Results Surveyed parents and affected children reported desire for future research addressing the vision loss in CLN3 disease, and lower quality of life in vision-related domains. One grade 1 adverse event was recorded during the study. Feasibility and Function assessments showed that > 90% of evaluable participants scored above thresholds on feasibility assessments and > 25% had improved scores and performance time on device-specific tasks. Conclusions The data provide indications for the safety, feasibility and task-specific efficacy for the OrCam MyEye 2. They support further, including longitudinal, evaluation and consideration of such optic-to-audio devices as part of the toolbox for low vision therapy for children with multiple disabilities such as CLN3 disease. Trial registration clinicaltrials.gov, NCT04974307. Registered 23 July 2021, https//clinicaltrials.gov/study/NCT04974307 .

Purpose:To establish an in vivo database of human cone photoreceptor inner segment diameter evaluated across the lifespan. Methods:Non-confocal split detection adaptive optics (AO) imaging was performed in 28 eyes of 28 healthy subjects (14 females and 14 males; 45.1 ± 20.7 years, ranging from 12-84 years). Cone photoreceptor inner segments were semi-automatically segmented and cone diameters measured from the AO images across eccentricities ranging from 1.0 to 6.0 mm temporal to the fovea. A linear mixed-effects model was used to assess the relationship between cone diameter and sex as well as cone diameter and age. Results:Cone photoreceptor inner segment diameter increased with increasing eccentricity (n = 9350 segmented cones), from an average of 5.0 µm (eccentricity: 1.0 mm) to 7.8 µm (6.0 mm). Overall, cone diameter in females was slightly greater (by an average of 5%) than cone diameter in males across most eccentricities measured. The differences in cone diameter between females and males could not be accounted for by differences in axial length or age. In addition, cone diameters in younger subjects were generally larger than those from older subjects. Conclusions:In vivo measurements of human cone photoreceptor inner segment diameter across the lifespan are necessary for future comparisons with data from age-related disease. Statistically significant differences due to both age and sex were observed.

Foveal hypoplasia causes visual impairment across congenital eye disorders, yet the genetic programmes governing foveal development remain poorly characterised and no tractable model exists for foveal disease. In the first genome-wide association study of foveal hypoplasia, we identified 42 sentinel variants mapping to 54 effector genes supported by ≥ 2 criteria from a variant-to-gene framework incorporating developmental multi-omics. Disruption of six effector genes using mutant lines and CRISPR knockouts in the zebrafish high acuity zone recapitulates structural, functional, and ultrastructural hallmarks of foveal hypoplasia, establishing the first vertebrate disease model. Integration with human foetal single-cell and spatial transcriptomics reveals two temporal waves of effector gene expression and identifies Müller glia as critical mediators of foveal patterning. Phenome-wide analyses reveal foveal variants are pleiotropic with refractive, lenticular, and metabolic traits, connecting foveal development to anterior segment and systemic disease biology. These findings should inform mechanistic studies of macular disease.

We describe a 45-year-old man with bilateral bifoveate retinas, an exceptionally rare human phenotype. Spectral-domain OCT demonstrated two distinct foveal pits per eye: a deep central fovea and a shallower temporal fovea with grade 1 foveal hypoplasia features. OCT-angiography revealed paired foveal avascular zones bilaterally. Unlike previously reported cases, which were predominantly unilateral and nonfunctional, both temporal foveae in this case show well-developed architecture closely resembling the bifoveate visual system of Anolis lizards. We propose this represents a rare partial failure of the spatial constraints that normally confine CYP26A1-mediated retinoic acid signaling to a single foveal locus in primates.

Oculocutaneous albinism type 1A (OCA1A), the most severe and prevalent form of albinism, is caused by recessive mutations in the TYROSINASE gene. We provide proof-of-principle of an effective gene therapy-based strategy for future human application in OCA1A patients. Here we show that an AAV based TYROSINASE gene delivery under the control of human BESTROPHIN promoter VMD2 can successfully induce pigmentation in human retinal pigment epithelium (RPE) monolayer tissue, derived from OCA1A patients, via induced pluripotent stem cells. Pigmentation was induced without significantly compromising the RPE monolayer tissue integrity, apical-basal polarization, cellular morphology, or functionally relevant gene expression patterns. This human RPE specific construct was able to induce pigmentation in albino rat RPE and choroid when delivered into eyes via suprachoroidal injection. Our strategy can be potentially employed to not only induce pigmentation, but also efficiently deliver other target genes, without significantly compromising monolayer tissue integrity and viability of human RPE, a prime gene therapy target tissue for many degenerative disorders affecting vision.

Heterogeneous degeneration of the retinal pigment epithelium (RPE) leads to irreversible blindness in diseases associated with macular atrophy. However, the underlying mechanisms of regional RPE degeneration remain poorly understood. To address this gap, this study identified a peripheral RPE subpopulation through spatial, transcriptomic, and functional analyses, thereby contributing to the understanding of the heterogeneity of degenerative RPE cells. Specifically, omics analyses in human and macaque RPE revealed a peripheral RPE cell population with high SERPINE3 expression, while SERPINE3-GFP-knockin mice showed comparable expression patterns. SMART RNA-seq2 analysis further distinguished transcriptomic profiles between GFP+ and GFP- RPE cells. Under oxidative stress, SERPINE3 expression increased, and GFP+ cells exhibited improved survival and reentry into the cell cycle. Notably, genetic studies indicated that SERPINE3 is essential for the oxidative stress resistance of GFP+ cells. Moreover, loss of SERPINE3 resulted in regional RPE degeneration and increased microglial accumulation in aged mice. Mechanistically, proteinase screening and co-IP indicated that SERPINE3 targets caspase-1. Importantly, delivery of SERPINE3 via AAV-Serpine3 partially reduced RPE degeneration in an oxidative damage model. These findings advance the understanding of RPE heterogeneous degeneration and highlight SERPINE3 as a protective factor with therapeutic potential for macular atrophy.

Purpose To investigate the role of Zfp503 in mammalian eye development. Methods Zfp503-/- and Zfp503+/- mice were successfully created through the Knockout Mouse Phenotyping Project (KOMP2), and abnormalities were noted through ophthalmic examination. Embryos were studied at E15.5. Postnatal mice were evaluated using electroretinography (ERG), fundus photography, fluorescein angiography, and optical coherence tomography (OCT) to examine phenotypic differences. Hematoxylin and eosin (H&E) staining was performed to evaluate the retina and optic nerve head (ONH) morphology, and immunohistochemistry was used to determine the expression pattern of Zfp503 in the mouse retina and in the human fetal retina. Results All homozygous Zfp503-/- embryos of both sexes exhibited hypopigmented eyes and/or anophthalmia and were postnatally non-viable. Histopathology showed hypopigmented retinal pigment epithelium (RPE). With H&E staining, homozygote animals showed failure of the optic fissure to close and what appears to be duplicated retinal tissue. All postnatal Zfp503+/- heterozygotes of both sexes displayed an atypical ONH coloboma. Fundus photography of heterozygotes showed a coloboma extending dorsally from the optic nerve head, and an area of abnormal fluorescence in the area associated with the coloboma region was seen on fluorescein angiography. Histopathology and cross-sectional optical coherence tomography (OCT) showed excavation of the ONH. Three-dimensional OCT reconstructions showed an outpouching consistent with coloboma of the ONH. Other systemic abnormalities in homozygous and heterozygous mice were present across both sexes. The human homolog ZNF503 was detected in fetal eyes. Conclusions Zfp503 deficiency led to poorly developed RPE and non-viability in Zfp503 knockout mice. Zfp503 heterozygous mice developed an atypical optic nerve coloboma. This study advances previous work by expanding the understanding of the optic nerve coloboma phenotype in heterozygous mice and demonstrating expression of ZNF503 in the developing human eye.

Purpose:To explore the phenotypic spectrum and genetic etiologies of Moebius Syndrome (MBS), a rare neurological disorder defined by congenital, nonprogressive facial weakness and limitations in ocular abduction. Methods:We applied strict diagnostic criteria and conducted clinical phenotyping of 149 individuals with MBS. Subsequently, we performed exome and/or genome sequencing on 67 of these individuals and 117 unaffected family members. Results:All 149 individuals had sporadic MBS, with no recurrence within or across generations. Common co-occurring phenotypes included tongue hypoplasia (81.9%), micrognathia (66.4%), congenital talipes equinovarus (42.3%), major limb anomalies (31.5%), intellectual disability (30.9%), sleep difficulties (22.8%), and Poland anomaly (14.1%). Filtering for rare de novo or autosomal recessive single-nucleotide, insertion/deletion, and structural variants in the sequenced cohort yielded 173 single-nucleotide variant/indels in 113 genes. Although we prioritized 7 candidate genes with de novo variants and 5 with biallelic variants, no compelling recurrently mutated genes were identified. Similarly, we found no convincing variants in 2 putative genes previously implicated in MBS: PLXND1 (HGNC:9107) and REV3L (HGNC:9968). Conclusion:We did not identify a strong or unifying germline genetic etiology for MBS. Future studies may explore alternative causes, including environmental exposures, somatic variants, and/or complex inheritance patterns affecting brainstem and organ embryogenesis.

We present a 2-year-old male with bilateral iris and chorioretinal colobomas, speech delays, and facial and digital anomalies. Trio exome sequencing demonstrated a de novo, novel heterozygous variant, c.379G>A p.Glu127Lys in CDC42, conferring a diagnosis of Takenouchi-Kosaki syndrome. The p.Glu127Lys variant was not located in the same region as previously designated mutation classes for CDC42, and the patient's missense substitution was predicted to disrupt CDC42 interactions with Collybistin II and IQGAP1. As conditional knock-out mouse models have demonstrated coloboma in association with loss of Cdc42 expression, we conclude that the colobomas can be attributed to the CDC42 variant and that similar ocular anomalies are likely to be described with other Rho GTPases in the future.

PURPOSE. The pathogenesis of uveal coloboma, a potentially blinding congenital ocular malformation, is incompletely understood. We characterize a novel mouse model of coloboma, Retinal and Iris Coloboma (RICO). METHODS. Transgenic mice were created by insertion of a human vascular endothelial growth factor-165 (hVEGF) gene driven by a neuron-specific enolase promoter. Mice were examined clinically and histologically, and the insertion site was characterized by fluorescence in situ hybridization and genomic sequencing. Gene expression changes were assessed with RNA sequencing, immunofluorescence, and in situ hybridization. RESULTS. RICO mice are viable in the homozygous state and exhibit fully penetrant autosomal semidominant coloboma. Coloboma is associated with persistence of periocular mesenchyme in the optic fissure, likely contingent on a specific, transgene insertioninduced genomic rearrangement on chromosome 13 that drives aberrant hVEGF expression. RICO eye cups exhibit altered expression of genes in the vicinity of the insertion site, where deletions of the human homologous locus were found in coloboma patients. RNA sequencing demonstrates changes in multiple coloboma-associated genes. CONCLUSIONS. RICO represents a useful model for studying the pathogenesis of human coloboma.

This chapter traces the normal development of the optic nerve throughout gestation before discussing aplasia of the optic nerve, a rare condition in which the optic nerve fails to develop, and optic nerve hypoplasia, a congenital, nonprogressive developmental abnormality characterized by reduced numbers of retinal ganglion cells and corresponding defects in the nerve fiber layer of the retina. Other conditions covered are duplication of the optic nerve, an extremely rare condition characterized by the presence of two separate nerves exiting from the globe, pseudo-duplication of the optic nerve, a developmental abnormality in which retinal vasculature appears to emerge from a second, often slightly cupped or excavated, location in the retina, and megalopapilla, an abnormally large optic disc with no anatomic defects. Cavitary malformations of the optic nerve, broadly referred to as “optic nerve coloboma” are also covered, including uveal coloboma; morning glory disc anomaly; PAX2-related congenital optic nerve anomalies (papillorenal syndrome); peripapillary staphyloma, a rare, non-progressive, congenital abnormality in which a relatively normal appearing optic nerve head sits at the base of a posterior pole excavation; and optic pits, excavations of variable color, depth, and location in the disc substance. Congenital tilted disc and congenital optic disc pigmentation are discussed, as are Bergmeister’s papilla, a benign anomaly that describes an optic nerve head with veil-like remnants of the primary vitreous in its center or covering it, and myelinated fibers. Finally, the chapter covers congenital vascular anomalies: prepapillary vascular loops, cilioretinal arteries, optociliary veins, and optic disc drusen.

Significant loss of pigmentation can increase visual disability, skin cancer risk, and psychosocial stress. Tyrosinase (TYR) catalyzes the first and rate-limiting step of melanin synthesis. Inhibitors of TYR are well established and are currently used in clinical settings; however, there is a dearth of direct activators of TYR. Here, using a unique human TYR construct, high-throughput screening, and computational analysis techniques, we identified ampyrone as a TYR activator. Ampyrone increased the in vitro catalytic activity of the intramelanosomal domain of human TYR (hTYR) and its hypomorphic variant, P406L, a cause of oculocutaneous albinism type 1B (OCA1B). Moreover, ampyrone induced melanin synthesis in both wild-type and OCA1B human melanocytes, as well as 3-dimension (3D) human skin cultures. Our results reveal ampyrone as a lead compound for first-in-class TYR activators, potentially accelerating the discovery of novel therapies for patients with genetic and acquired diseases of hypopigmentation.

BACKGROUND:Advancements in biomedical optical imaging have enabled researchers to achieve cellular-level imaging in the living human body. However, research-grade technology is not always widely available in routine clinical practice. In this paper, we incorporated artificial intelligence (AI) with standard clinical imaging to successfully obtain images of the retinal pigment epithelial (RPE) cells in living human eyes. METHODS:Following intravenous injection of indocyanine green (ICG) dye, subjects were imaged by both conventional instruments and adaptive optics (AO) ophthalmoscopy. To improve the visibility of RPE cells in conventional ICG images, we demonstrate both a hardware approach using a custom lens add-on and an AI-based approach using a stratified cycleGAN network. RESULTS:We observe similar fluorescent mosaic patterns arising from labeled RPE cells on both conventional and AO images, suggesting that cellular-level imaging of RPE may be obtainable using conventional imaging, albeit at lower resolution. Results show that higher resolution ICG RPE images of both healthy and diseased eyes can be obtained from conventional images using AI with a potential 220-fold improvement in time. CONCLUSIONS:The application of using AI as an add-on module for existing instrumentation is an important step towards routine screening and detection of disease at earlier stages.

Purpose:The RM Electrode is a new, single-use, soft-contact lens electrode for recording the full-field electroretinogram (ffERG). Aims were (1) to define the ffERG reference ranges for the RM Electrode, with age, from healthy volunteers and (2) to compare ffERGs recorded with the RM Electrode and Burian-Allen (BA) electrode. Methods:The ffERGs were recorded using the International Society of Clinical Electrophysiology of Vision (ISCEV) standard, including four ISCEV extended protocols: dark-adapted red flash, photopic negative response, ON-OFF, and S-cones. Electroretinogram (ERG) parameters and recording stability, measured from the percent coefficient of variation (%CV), were compared across electrodes. Results:Participants were 40 (19 female) healthy volunteers aged 39.4 ± 15.7 years. Participants' race (white/black/Asian = 58%/20%/18%) and ethnicity (Hispanic = 10%) were congruent with the US 2020 Census. All amplitudes and implicit times followed a log-normal distribution (except photopic b-wave and ON-OFF amplitudes); most parameters varied with age. RM Electrode dark-adapted a-wave and light-adapted b-wave amplitudes were 18% (P = 0.02) and 20% (P < 0.001) larger than the BA electrode; scotopic b-wave amplitudes did not differ. The 30-Hz ERGs were more stable for the RM Electrode (median [interquartile range] %CV = 12.3% [7.6-17.6]) compared with the BA electrode (%CV = 16.7% [12.5-26.8] (P = 0.001). Conclusions:RM Electrode parameters and interflash ERG stability were comparable to or better than those for the BA electrode. Translational Relevance:The derived reference ranges for the RM Electrode allow easy adoption of this disposable contact lens electrode that mitigates possible cross-contamination between patients.

PURPOSE:Uveal coloboma may be an isolated finding or present as part of a syndrome, informed by systemic testing. Genetic testing may elucidate an underlying cause of disease. The likelihood of developmental delay in children with coloboma has not been well-studied. We examined the rates of developmental delay in coloboma patients with syndromic vs nonsyndromic presentations and with positive and negative molecular diagnoses. METHODS:Seventy patients with coloboma underwent a battery of systemic testing, molecular diagnosis, and cognitive and/or adaptive behavioral testing between 2009 and 2023. Patients with ≥2 abnormal systemic findings, excluding ocular or developmental delay, were classified as syndromic. The associations between delay and syndromic diagnosis or positive molecular testing were analyzed with logistic regression. RESULTS:The mean age of participants was 3.97 years. Twenty-three patients were syndromic. Causative variants were identified in 13 cases. Individuals with a syndromic presentation had greater odds of having or reporting developmental delay than those with a nonsyndromic presentation (odds ratio [95% confidence interval] = 4.81 [1.67, 14.69], Z = 2.85, P = .004). A syndromic diagnosis also increased the likelihood of having a solved genetic diagnosis (odds ratio [95% confidence interval] = 6.91 [1.94, 28.89], Z = 2.86, P = .004). CONCLUSIONS:Systemic findings are common in patients presenting with isolated coloboma, underscoring the need for deep phenotyping. In our study, a molecular diagnosis was obtained in only a minority, implying undiscovered genetic or environmental factors. Those patients with ≥2 systemic findings were more likely to be developmentally delayed and to have a positive molecular diagnosis. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.