Deprivation amblyopia and congenital hereditary cataract

Combined trabeculotomy-trabeculectomy for glaucoma after congenital cataract surgery: long-term results

OBJECTIVE

The aim of this study was to report on the long-term (>5 years) results of surgery for glaucoma after congenital cataract surgery.

DESIGN

Retrospective.

METHODS

A chart review was conducted of all children operated on for glaucoma after congenital cataract surgery in the Pediatric Ophthalmology Service of the Ophthalmology Department of Alexandria main University Hospital in Alexandria, Egypt, between 2005 and 2014 who completed 5 years of follow-up. Demographic, clinical, and operative data were retrieved from the medical records. Success was defined by stability and (or) reversal of optic nerve cupping in relation to presentation and, if this information was not available, by an intraocular pressure (IOP) less than the presenting IOP and less than 16 mm Hg with (true) or without (qualified) IOP-lowering therapy.

RESULTS

The records of 48 children were reviewed. Thirty-two eyes of 24 children had completed at least 5 years of follow-up and were included in the study. The mean age (±SD) of the study children was 11.6 ± 11.3 months (range, 3.2-52.0 months) at presentation, and the mean (±SD) follow-up was 105.5 ± 31.4 months (range, 60-156 months). Of 47 glaucoma surgical procedures in total, combined angle and filtering surgery with antimetabolite was the most common procedure performed (n = 30;63.8%). Annual success percentages from the fifth year onward to the thirteenth year were 69.6%, 68.8%, 77.8%, 50.0%, 71.4%, 60.0%, 50.0%, 83.3%, and 50.0%, respectively.

CONCLUSIONS

Surgery for glaucoma after congenital cataract surgery remains safe and successful for 13 years after surgery.

Current Developments in the Management of Amblyopia with the Use of Perceptual Learning Techniques

Background and Objectives: Amblyopia is a neurodevelopmental disorder caused by interocular suppression of visual input, affecting visual acuity, stereopsis, contrast sensitivity, and other visual functions. Conventional treatment comprises occlusion of the sound eye. In recent years, novel therapies that deploy perceptual learning (PL) principles have been introduced. The purpose of this study is to assess the latest scientific data on this topic. Materials and Methods: For this purpose, we conducted a literature search for relevant studies published during the previous 4 years (2020-2023). Results: A plethora of visual perceptual learning protocols have been recently developed. Dichoptic video games, contrast rebalanced movies, and online perceptual training platforms are the main formats. Perceptual learning activates neuroplasticity, overcomes interocular suppression, and improves the visual impairments induced by amblyopia. Conclusions: This novel treatment is effective in both children and adults, as well as in patients non-responding to patching.

Congenital cataracts affect the retinal visual cycle and mitochondrial function: A multi-omics study of GJA8 knockout rabbits

Congenital cataracts are a threat to visual development in children, and the visual impairment persists after surgical treatment; however, the mechanisms involved remain unclear. Previous clinical studies have identified the effect of congenital cataracts on retinal morphology and function. To further understand the molecular mechanisms by which congenital cataracts affect retinal development, we analyzed retina samples from 7-week-old GJA8-knockout rabbits with congenital cataracts and controls by four-dimensional label-free quantification proteomics and untargeted metabolomics. Bioinformatics analysis of proteomic data showed that retinol metabolism, oxidative phosphorylation, and fatty acid degradation pathways were downregulated in the retinas of rabbits with congenital cataracts, indicating that their visual cycle and mitochondrial function were affected. Additional validation of differentially abundant proteins related to the visual cycle and mitochondrial function was performed using Parallel reaction monitoring and western blot experiments. Untargeted metabolome analysis showed significant upregulation of the antioxidant glutathione and ascorbic acid in the retinas of rabbits with congenital cataracts, indicating that their oxidative stress balance was not dysregulated. SIGNIFICANCE: Congenital cataracts in children can alter retinal structure and function, yet the mechanisms are uncertain. Here is the first study to use proteomics and metabolomics approaches to investigate the effects of congenital cataracts on retinal development in the early postnatal period. Our findings suggest that congenital cataracts have an impact on the retinal visual cycle and mitochondrial function. These findings give insight on the molecular pathways behind congenital cataract-induced visual function impairment in the early postnatal period.

Insight into Pathogenic Mechanism Underlying the Hereditary Cataract Caused by βB2-G149V Mutation

Congenital cataracts account for approximately 5-20% of childhood blindness worldwide and 22-30% of childhood blindness in developing countries. Genetic disorders are the primary cause of congenital cataracts. In this work, we investigated the underlying molecular mechanism of G149V point missense mutation in βB2-crystallin, which was first identified in a three-generation Chinese family with two affected members diagnosed with congenital cataracts. Spectroscopic experiments were performed to determine the structural differences between the wild type (WT) and the G149V mutant of βB2-crystallin. The results showed that the G149V mutation significantly changed the secondary and tertiary structure of βB2-crystallin. The polarity of the tryptophan microenvironment and the hydrophobicity of the mutant protein increased. The G149V mutation made the protein structure loose and the interaction between oligomers was reduced, which decreased the stability of the protein. Furthermore, we compared βB2-crystallin WT and the G149V mutant with their biophysical properties under environmental stress. We found that the G149V mutation makes βB2-crystallin more sensitive to environmental stresses (oxidative stress, UV irradiation, and heat shock) and more likely to aggregate and form precipitation. These features might be important to the pathogenesis of βB2-crystallin G149V mutant related to congenital cataracts.

Surgical Outcomes of Lensectomy-Vitrectomy with Primary Intraocular Lens Implantation in Children with Bilateral Congenital Cataracts

In this study, we evaluated the long-term surgical outcomes of lensectomy-vitrectomy with primary intraocular lens (IOL) implantation in children with bilateral congenital cataracts (CCs) and investigated the potential risk factors for low vision. A total of 148 eyes in 74 children who underwent lensectomy-vitrectomy with primary IOL implantation were enrolled in this study. The surgery age was 44.04 ± 14.60 months, with a follow-up period of 46.66 ± 14.34 months. The final BCVA was 0.24 ± 0.32 logMAR, and low vision was found in 22 eyes (14.9%). Postoperative complications requiring additional surgeries included VAO (4 eyes, 5.4%), IOL pupillary captures (2 eyes, 2.0%), iris incarceration (1 eye, 0.7%), and glaucoma (1 eye, 0.7%). A higher incidence of VAO and larger postoperative refractive error was observed in younger children (≤2 years old) than in elder children (>2 years old) (p = 0.003, p = 0.047, respectively). Final BCVA was affected by preexisting comorbidity (p < 0.001), cataract density (p < 0.001), cataract size (p = 0.020), occurrence of postoperative complications (p = 0.011), and ASE (p = 0.008). Multivariate analysis showed that denser cataracts (OR = 9.303, p = 0.035) and preexisting comorbidity (OR = 4.712, p = 0.004) were the significant predictors of low vision. In conclusion, lensectomy-vitrectomy with primary IOL implantation is an effective and safe treatment for CC. The long-term visual outcome is encouraging in children with bilateral CC undergoing this procedure with a low rate of postoperative complications requiring surgeries. Moreover, eyes with denser cataracts and preexisting comorbidity may have a high risk of low vision.

Case Report: A Novel Mutation in the CRYGD Gene Causing Congenital Cataract Associated with Nystagmus in a Chinese Family

Purpose: Congenital cataract (CC) is a common disease resulting in leukocoria and the leading cause of blindness in children worldwide. Approximately 50% of congenital cataract is inherited. Our aim is to identify mutations in a Chinese family with congenital cataract.

Methods: A four-generation Chinese family diagnosed with congenital cataract was recruited in West China Hospital of Sichuan University. Genomic DNA was extracted from the peripheral blood of these participants. All coding exons and flanking regions were amplified and sequenced, and the variants were validated using Sanger sequencing. AlphaFold2 was used to predict possible protein structural changes in this variant.

Results: The proband had congenital nuclear cataract with nystagmus. A heterozygous variant c.233C &gt; T was identified in exon 2 of the CRYGD gene in chromosome 2. This mutation resulted in a substitution of serine with phenylalanine at amino acid residue 78 (p.S78F). The variant might result in a less stable structure with a looser loop and broken hydrogen bond predicted by AlphaFold2, and this mutation was co-segregated with the disease phenotype in this family.

Conclusion: We described cases of human congenital cataract caused by a novel mutation in the CRYGD gene and provided evidence of further phenotypic heterogeneity associated with this variant. Our study further extends the mutation spectrum of the CRYGD gene in congenital cataract.

Prevalence of Pediatric Cataract in Asia: A Systematic Review and Meta-Analysis

Purpose:

To conduct a systematic review and meta-analysis for estimating the prevalence of pediatric cataracts across Asia.

Methods:

A detailed literature search of PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar databases, from 1990 to July 2021, was performed to include all studies reporting the prevalence of cataracts among children. Two researchers performed the literature search and screening of articles independently, and a third researcher critically reviewed the overall search and screening process to ensure the consistency. The JBI Critical Appraisal Checklist for studies reporting prevalence data was used to assess the methodological quality of the included studies.

Results:

Of the 496 identified articles, 35 studies with a sample size of 1,168,814 from 12 Asian countries were included in this analysis. The estimated pooled prevalence of pediatric cataracts in Asian children is 3.78 (95% confidence interval: 2.54–5.26)/10,000 individuals with high heterogeneity (I^[2] = 89.5%). The pooled prevalence by each country per 10,000 was 0.60 in Indonesia, 0.92 in Bangladesh, 1.47 in Iran, 2.01 in Bhutan, 3.45 in Laos, 3.68 in China, 4.27 in Thailand, 4.47 in India, 5.33 in Malaysia, 5.42 in Nepal, 9.34 in Vietnam, and 10.86 in Cambodia.

Conclusions:

This study utilizes existing literature to identify the prevalence of cataracts in Asian children. Moreover, it highlights the need for more epidemiological studies with large sample sizes from other countries in Asia to accurately estimate the burden of disease.

The Tudor-domain protein TDRD7, mutated in congenital cataract, controls the heat shock protein HSPB1 (HSP27) and lens fiber cell morphology

Mutations of the RNA granule component TDRD7 (OMIM: 611258) cause pediatric cataract. We applied an integrated approach to uncover the molecular pathology of cataract in Tdrd7-/- mice. Early postnatal Tdrd7-/- animals precipitously develop cataract suggesting a global-level breakdown/misregulation of key cellular processes. High-throughput RNA sequencing integrated with iSyTE-bioinformatics analysis identified the molecular chaperone and cytoskeletal modulator, HSPB1, among high-priority downregulated candidates in Tdrd7-/- lens. A protein fluorescence two-dimensional difference in-gel electrophoresis (2D-DIGE)-coupled mass spectrometry screen also identified HSPB1 downregulation, offering independent support for its importance to Tdrd7-/- cataractogenesis. Lens fiber cells normally undergo nuclear degradation for transparency, posing a challenge: how is their cell morphology, also critical for transparency, controlled post-nuclear degradation? HSPB1 functions in cytoskeletal maintenance, and its reduction in Tdrd7-/- lens precedes cataract, suggesting cytoskeletal defects may contribute to Tdrd7-/- cataract. In agreement, scanning electron microscopy (SEM) revealed abnormal fiber cell morphology in Tdrd7-/- lenses. Further, abnormal phalloidin and wheat germ agglutinin (WGA) staining of Tdrd7-/- fiber cells, particularly those exhibiting nuclear degradation, reveals distinct regulatory mechanisms control F-actin cytoskeletal and/or membrane maintenance in post-organelle degradation maturation stage fiber cells. Indeed, RNA immunoprecipitation identified Hspb1 mRNA in wild-type lens lysate TDRD7-pulldowns, and single-molecule RNA imaging showed co-localization of TDRD7 protein with cytoplasmic Hspb1 mRNA in differentiating fiber cells, suggesting that TDRD7-ribonucleoprotein complexes may be involved in optimal buildup of key factors. Finally, Hspb1 knockdown in Xenopus causes eye/lens defects. Together, these data uncover TDRD7's novel upstream role in elevation of stress-responsive chaperones for cytoskeletal maintenance in post-nuclear degradation lens fiber cells, perturbation of which causes early-onset cataracts.

Evaluation of changes in axial length after congenital cataract surgery

PURPOSE

To investigate the relationship between lens status and axial length (AL) in patients operated for unilateral and bilateral congenital cataract.

SETTING

Yüzüncü Yıl University, Ophthalmology Clinic, Van, Turkey.

DESIGN

Retrospective study.

METHODS

Records of patients who underwent surgery for unilateral or bilateral congenital cataract were analyzed. The patients were separated into three groups: bilateral aphakic, bilateral pseudophakic, and unilateral. The unilateral group was subdivided into the operated cataract eyes (unilateral aphakic and unilateral pseudophakic) and unoperated fellow phakic eyes. The patients' age at surgery, follow-up time, preoperative and postoperative AL measurements, change in AL, and monthly growth rate were evaluated.

RESULTS

The bilateral aphakic group included 40 eyes of 20 patients, the bilateral pseudophakic group included 103 eyes of 54 patients, and the unilateral group included 40 eyes of 20 patients. The mean age at time of surgery in these groups was 8.17 months ± 10.65 (SD), 42.47 ± 43.81 months, and 42.47 ± 43.81 months, respectively. There were no significant differences in preoperative AL, postoperative AL, change in AL, or monthly growth rate between the aphakic and fellow phakic eyes in the unilateral group (P > .05). There were also no significant differences between unilateral pseudophakic eyes and fellow phakic eyes in the unilateral group with respect to preoperative AL or change in AL, but there were significant differences in final AL and monthly growth rate (P < .05).

CONCLUSIONS

Various factors can affect axial elongation. The monthly growth rate was lower in pseudophakic eyes compared with phakic eyes. Experimental studies are required to understand the mechanism underlying this effect.

Dynamic response to initial stage blindness in visual system development

Sensitive periods and experience-dependent plasticity have become core issues in visual system development. Converging evidence indicates that visual experience is an indispensable factor in establishing mature visual system circuitry during sensitive periods and the visual system exhibits substantial plasticity while facing deprivation. The mechanisms that underlie the environmental regulation of visual system development and plasticity are of great interest but need further exploration. Here, we investigated a unique sample of human infants who experienced initial stage blindness (beginning at birth and lasting for 2–8 months) before the removal of bilateral cataracts. Retinal thickness (RT), axial length (AL), refractive status, visual grating acuity and genetic integrity were recorded during the preoperative period or at surgery and then during follow-up. The results showed that the development of the retina is malleable and associated with external environmental influences. Our work supported that the retina might play critical roles in the development of the experience-dependent visual system and its malleability might partly contribute to the sensitive period plasticity.

RNA-binding proteins in eye development and disease: implication of conserved RNA granule components

The molecular biology of metazoan eye development is an area of intense investigation. These efforts have led to the surprising recognition that although insect and vertebrate eyes have dramatically different structures, the orthologs or family members of several conserved transcription and signaling regulators such as Pax6, Six3, Prox1, and Bmp4 are commonly required for their development. In contrast, our understanding of posttranscriptional regulation in eye development and disease, particularly regarding the function of RNA-binding proteins (RBPs), is limited. We examine the present knowledge of RBPs in eye development in the insect model Drosophila as well as several vertebrate models such as fish, frog, chicken, and mouse. Interestingly, of the 42 RBPs that have been investigated for their expression or function in vertebrate eye development, 24 (~60%) are recognized in eukaryotic cells as components of RNA granules such as processing bodies, stress granules, or other specialized ribonucleoprotein (RNP) complexes. We discuss the distinct developmental and cellular events that may necessitate potential RBP/RNA granule-associated RNA regulon models to facilitate posttranscriptional control of gene expression in eye morphogenesis. In support of these hypotheses, three RBPs and RNP/RNA granule components Tdrd7, Caprin2, and Stau2 are linked to ocular developmental defects such as congenital cataract, Peters anomaly, and microphthalmia in human patients or animal models. We conclude by discussing the utility of interdisciplinary approaches such as the bioinformatics tool iSyTE (integrated Systems Tool for Eye gene discovery) to prioritize RBPs for deriving posttranscriptional regulatory networks in eye development and disease. WIREs RNA 2016, 7:527-557. doi: 10.1002/wrna.1355 For further resources related to this article, please visit the WIREs website.

Amblyopia screening in Bulgaria

PURPOSE

To determine the prevalence of amblyopia and the average age at first ophthalmological examination of school-aged children from northwestern Bulgaria.

METHODS

Visual acuity testing, stereopsis, orthoptics, ocular motility, non-cycloplegic refraction, direct ophthalmoscopy, and external ocular inspection were performed. Cycloplegic refraction and indirect ophthalmoscopy were done as necessary. A total of 2,054 children (1,020 girls and 1,034 boys) were divided into three age groups: 6 to 8 years (803 children), 8 to 10 years (719 children), and 10 to 12 years (530 children).

RESULTS

A total of 1,861 children (90.6%) received their first examination: 754 (93.9%) aged 6 to 8 years, 638 (88.7%) aged 8 to 10 years, and 469 (88.2%) aged 10 to 12 years. Amblyopia was detected in 88 children (4.3%): 42 (5.2%) aged 6 to 8 years, 27 (3.8%) aged 8 to 10 years, and 19 (3.6%) aged 10 to 12 years. The first group had higher prevalence compared to countries with well-developed screening programs. Refractive errors were detected in 403 children (19.7%): 125 (15.6%) aged 6 to 8 years, 146 (20.3%) aged 8 to 10 years, and 132 (24.8%) aged 10 to 12 years. The estimated prevalence increases with age. Strabismus was detected in 24 children (1.2%): 8 (1.0%) aged 6 to 8 years, 7 (1.0%) aged 8 to 10 years, and 9 (1.7%) aged 10 to 12 years.

CONCLUSIONS

The lack of screening programs in Bulgaria is the main reason for late diagnosis of amblyopia. The "Do Good "project provided eye examination of school-aged children aged 6 to 12 years, when amblyopia is curable. This model could be used in establishing a Bulgarian national screening program.