Congenital Stationary Night Blindness: Clinical and Genetic Features.

Congenital stationary night blindness (CSNB) is an inherited retinal disease (IRD) that causes night blindness in childhood with heterogeneous genetic, electrophysical, and clinical characteristics. The development of sequencing technologies and gene therapy have increased the ease and urgency of diagnosing IRDs. This study describes seven Taiwanese patients from six unrelated families examined at a tertiary referral center, diagnosed with CSNB, and confirmed by genetic testing. Complete ophthalmic exams included best corrected visual acuity, retinal imaging, and an electroretinogram. The effects of identified novel variants were predicted using clinical details, protein prediction tools, and conservation scores. One patient had an autosomal dominant CSNB with a RHO variant; five patients had complete CSNB with variants in GRM6, TRPM1, and NYX; and one patient had incomplete CSNB with variants in CACNA1F. The patients had Riggs and Schubert-Bornschein types of CSNB with autosomal dominant, autosomal recessive, and X-linked inheritance patterns. This is the first report of CSNB patients in Taiwan with confirmed genetic testing, providing novel perspectives on molecular etiology and genotype-phenotype correlation of CSNB. Particularly, variants in TRPM1, NYX, and CACNA1F in our patient cohort have not previously been described, although their clinical significance needs further study. Additional study is needed for the genotype-phenotype correlation of different mutations causing CSNB. In addition to genetic etiology, the future of gene therapy for CSNB patients is reviewed and discussed.

BEST1 gene therapy corrects a diffuse retina-wide microdetachment modulated by light exposure.

Mutations in the BEST1 gene cause detachment of the retina and degeneration of photoreceptor (PR) cells due to a primary channelopathy in the neighboring retinal pigment epithelium (RPE) cells. The pathophysiology of the interaction between RPE and PR cells preceding the formation of retinal detachment remains not well-understood. Our studies of molecular pathology in the canine BEST1 disease model revealed retina-wide abnormalities at the RPE-PR interface associated with defects in the RPE microvillar ensheathment and a cone PR-associated insoluble interphotoreceptor matrix. In vivo imaging demonstrated a retina-wide RPE-PR microdetachment, which contracted with dark adaptation and expanded upon exposure to a moderate intensity of light. Subretinal BEST1 gene augmentation therapy using adeno-associated virus 2 reversed not only clinically detectable subretinal lesions but also the diffuse microdetachments. Immunohistochemical analyses showed correction of the structural alterations at the RPE-PR interface in areas with BEST1 transgene expression. Successful treatment effects were demonstrated in three different canine BEST1 genotypes with vector titers in the 0.1-to-5E11 vector genomes per mL range. Patients with biallelic BEST1 mutations exhibited large regions of retinal lamination defects, severe PR sensitivity loss, and slowing of the retinoid cycle. Human translation of canine BEST1 gene therapy success in reversal of macro- and microdetachments through restoration of cytoarchitecture at the RPE-PR interface has promise to result in improved visual function and prevent disease progression in patients affected with bestrophinopathies.

Inherited Retinal Diseases Due to RPE65 Variants: From Genetic Diagnostic Management to Therapy.

Inherited retinal diseases (IRDs) are a heterogeneous group of conditions that include retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA) and early-onset severe retinal dystrophy (EO[S]RD), which differ in severity and age of onset. IRDs are caused by mutations in >250 genes. Variants in the RPE65 gene account for 0.6-6% of RP and 3-16% of LCA/EORD cases. Voretigene neparvovec is a gene therapy approved for the treatment of patients with an autosomal recessive retinal dystrophy due to confirmed biallelic RPE65 variants (RPE65-IRDs). Therefore, the accurate molecular diagnosis of RPE65-IRDs is crucial to identify 'actionable' genotypes-i.e., genotypes that may benefit from the treatment-and is an integral part of patient management. To date, hundreds of RPE65 variants have been identified, some of which are classified as pathogenic or likely pathogenic, while the significance of others is yet to be established. In this review, we provide an overview of the genetic diagnostic workup needed to select patients that could be eligible for voretigene neparvovec treatment. Careful clinical characterization of patients by multidisciplinary teams of experts, combined with the availability of next-generation sequencing approaches, can accelerate patients' access to available therapeutic options.

Ocular genetics in the genomics age.

Current genetic screening methods for inherited eye diseases are concentrated on the coding exons of known disease genes (gene panels, clinical exome). These tests have a variable and often limited diagnostic rate depending on the clinical presentation, size of the gene panel and our understanding of the inheritance of the disorder (with examples described in this issue). There are numerous possible explanations for the missing heritability of these cases including undetected variants within the relevant gene (intronic, up/down-stream and structural variants), variants harbored in genes outside the targeted panel, intergenic variants, variants undetectable by the applied technology, complex/non-Mendelian inheritance, and nongenetic phenocopies. In this article we further explore and review methods to investigate these sources of missing heritability.

Ophthalmic genetics in South America.

South America comprises of heterogeneous topographies, populations, and health care systems. Therefore, it is not surprising to see differences among the countries regarding expertise, education, and practices of ophthalmic genetics for patients with rare eye diseases. Nevertheless, common challenges such as limited genetics training in medical schools and among ophthalmologists, scarcity of diagnostic tools for phenotyping, and expensive genetic testing not covered by the public healthcare systems, are seen in all of them. Here, we provide a detailed report of the current status of ophthalmic genetics, described by the personal views of local ophthalmologists from Brazil, Colombia, Argentina, and Chile. By reporting our strengths and weaknesses as a region, we intend to highlight the need for guidelines on how to manage these patients aligned with public health policies. Our region contributes to research worldwide, with thousands of well diagnosed patients from a number of unique and genetically diverse populations. The constant expansion of ophthalmic genetics and molecular diagnostics requires us to join forces to collaborate across South America and with other countries to improve access to next-generation diagnostics and ultimately improve patient care.

Ophthalmic genetics practice and research in India: Vision in 2020.

Ophthalmic genetics is a much needed and growing area in India. Ethnic diversity, with a high degree of consanguinity, has led to a high prevalence of genetic disorders in the country. As the second most populous country in the world, this naturally results in a significant number of affected people overall. Practice involves coherent association between ophthalmologists, genetic counselor and pediatricians. Eye genetics in India in recent times has witnessed advanced research using cutting edge diagnostics, next generation sequencing (NGS) approaches, stem cell therapies, gene therapy and genomic editing. This article will highlight the studies reporting genetic variations in the country, challenges in practice, and the latest advances in ophthalmic genetic research in India.

Genetic testing for inherited eye conditions in over 6,000 individuals through the eyeGENE network.

Genetic testing in a multisite clinical trial network for inherited eye conditions is described in this retrospective review of data collected through eyeGENE®, the National Ophthalmic Disease Genotyping and Phenotyping Network. Participants in eyeGENE were enrolled through a network of clinical providers throughout the United States and Canada. Blood samples and clinical data were collected to establish a phenotype:genotype database, biorepository, and patient registry. Data and samples are available for research use, and participants are provided results of clinical genetic testing. eyeGENE utilized a unique, distributed clinical trial design to enroll 6,403 participants from 5,385 families diagnosed with over 30 different inherited eye conditions. The most common diagnoses given for participants were retinitis pigmentosa (RP), Stargardt disease, and choroideremia. Pathogenic variants were most frequently reported in ABCA4 (37%), USH2A (7%), RPGR (6%), CHM (5%), and PRPH2 (3%). Among the 5,552 participants with genetic testing, at least one pathogenic or likely pathogenic variant was observed in 3,448 participants (62.1%), and variants of uncertain significance in 1,712 participants (30.8%). Ten genes represent 68% of all pathogenic and likely pathogenic variants in eyeGENE. Cross-referencing current gene therapy clinical trials, over a thousand participants may be eligible, based on pathogenic variants in genes targeted by those therapies. This article is the first summary of genetic testing from thousands of participants tested through eyeGENE, including reports from 5,552 individuals. eyeGENE provides a launching point for inherited eye research, connects researchers with potential future study participants, and provides a valuable resource to the vision community.

Inherited Eye Diseases with Retinal Manifestations through the Eyes of Homeobox Genes.

Retinal development is under the coordinated control of overlapping networks of signaling pathways and transcription factors. The paper was conceived as a review of the data and ideas that have been formed to date on homeobox genes mutations that lead to the disruption of eye organogenesis and result in inherited eye/retinal diseases. Many of these diseases are part of the same clinical spectrum and have high genetic heterogeneity with already identified associated genes. We summarize the known key regulators of eye development, with a focus on the homeobox genes associated with monogenic eye diseases showing retinal manifestations. Recent advances in the field of genetics and high-throughput next-generation sequencing technologies, including single-cell transcriptome analysis have allowed for deepening of knowledge of the genetic basis of inherited retinal diseases (IRDs), as well as improve their diagnostics. We highlight some promising avenues of research involving molecular-genetic and cell-technology approaches that can be effective for IRDs therapy. The most promising neuroprotective strategies are aimed at mobilizing the endogenous cellular reserve of the retina.

Sensing through Non-Sensing Ocular Ion Channels.

Ion channels are membrane-spanning integral proteins expressed in multiple organs, including the eye. In the eye, ion channels are involved in various physiological processes, like signal transmission and visual processing. A wide range of mutations have been reported in the corresponding genes and their interacting subunit coding genes, which contribute significantly to an array of blindness, termed ocular channelopathies. These mutations result in either a loss- or gain-of channel functions affecting the structure, assembly, trafficking, and localization of channel proteins. A dominant-negative effect is caused in a few channels formed by the assembly of several subunits that exist as homo- or heteromeric proteins. Here, we review the role of different mutations in switching a "sensing" ion channel to "non-sensing," leading to ocular channelopathies like Leber's congenital amaurosis 16 (LCA16), cone dystrophy, congenital stationary night blindness (CSNB), achromatopsia, bestrophinopathies, retinitis pigmentosa, etc. We also discuss the various in vitro and in vivo disease models available to investigate the impact of mutations on channel properties, to dissect the disease mechanism, and understand the pathophysiology. Innovating the potential pharmacological and therapeutic approaches and their efficient delivery to the eye for reversing a "non-sensing" channel to "sensing" would be life-changing.

Optogenetic approaches to vision restoration.

Inherited retinal disease (IRD) affects about 1 in 3000 to 1 in 5000 individuals and is now believed to be the most common cause of blindness registration in developed countries. Until recently, the management of such conditions had been exclusively supportive. However, advances in molecular biology and medical engineering have now seen the rise of a variety of approaches to restore vision in patients with IRDs. Optogenetic approaches are primarily aimed at rendering secondary and tertiary neurons of the retina light-sensitive in order to replace degenerate or dysfunctional photoreceptors. Such approaches are attractive because they provide a "causative gene-independent" strategy, which may prove suitable for a variety of patients with IRD. We discuss theoretical and practical considerations in the selection of optogenetic molecules, vectors, surgical approaches and review previous trials of optogenetics for vision restoration. Optogenetic approaches to vision restoration have yielded promising results in pre-clinical trials and a phase I/II clinical trial is currently underway (ClinicalTrials.gov NCT02556736). Despite the significant inroads made in recent years, the ideal optogenetic molecule, vector and surgical approach have yet to be established.

Gene therapy and the adeno-associated virus in the treatment of genetic and acquired ophthalmic diseases in humans: Trials, future directions and safety considerations.

Voretigene neparvovec-rzyl was recently approved for the treatment of Leber congenital amaurosis, and the use of gene therapy for eye disease is attracting even greater interest. The eye has immune privileged status, is easily accessible, requires a reduced dosage of therapy due to its size and is highly compartmentalized, significantly reducing systemic spread. Adeno-associated virus (AAV), with its low pathogenicity, prolonged expression profile and ability to transduce multiple cell types, has become the leading gene therapy vector. Target diseases have moved beyond currently untreatable inherited dystrophies to common, partially treatable acquired conditions such as exudative age-related macular degeneration and glaucoma, but use of the technology in these conditions imposes added obligations for caution in vector design. This review discusses the current status of AAV gene therapy trials in genetic and acquired ocular diseases, and explores new scientific developments, which could help ensure effective and safe use of the therapy in the future.

[Overview of Congenital Stationary Night Blindness with Predominantly Normal Fundus Appearance]. / Überblick über die kongenitale stationäre Nachtblindheit mit überwiegend normalem Fundus.

Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous group of non-progressive retinal disorder with largely normal fundus appearance. The mode of inheritance can be autosomal dominant (adCSNB), autosomal recessive (arCSNB) or X-chromosomal (XLCSNB). Additional ocular signs can be myopia, hyperopia, strabismus, nystagmus and reduced visual acuity. The Riggs and Schubert-Bornschein form of CSNB can be discriminated by electroretinography. While the Riggs form represents a dysfunction of the rods, a signal transmission defect from photoreceptors to bipolar cell is described in patients with the more frequently occurring Schubert-Bornschein form. The Schubert-Bornschein form can be further divided into incomplete (icCSNB) and complete (cCSNB) showing different electroretinograms (ERGs). While patients with cCSNB show a dysfunction of the ON-signaling pathway, patients with icCSNB show a dysfunction of the ON- and OFF-signaling pathways, affecting visual acuity as well. Using classical linkage, candidate gene analyses and more recent next-generation sequencing approaches, to date, mutations in 13 different genes have been associated with this disease. In vitro and in vivo models showed a correlation of the phenotype of patients with the expression, protein localization and function of the respective molecules: genes, mutated in patients with the Riggs form of CSNB have an important role in the rod phototransduction cascade. Genes mutated in patients with icCSNB, code for proteins important for glutamate neurotransmitter release at the synaptic cleft of the photoreceptors. Genes mutated in patients with cCSNB, code for proteins important for glutamate uptake and further signal transmission to the ON-bipolar cells. Preliminary in vivo studies showed that CSNB may be cured by gene therapy. These studies concerning CSNB are important for the precise diagnosis of patients with this disease, but are also helpful in deciphering key molecules essential for signal transmission from photoreceptors to bipolar cells. So far, it is a poorly understood field.

CLINICAL PROGRESS IN INHERITED RETINAL DEGENERATIONS: GENE THERAPY CLINICAL TRIALS AND ADVANCES IN GENETIC SEQUENCING.

PURPOSE: Inherited retinal dystrophies are a significant cause of vision loss and are characterized by the loss of photoreceptors and the retinal pigment epithelium (RPE). Mutations in approximately 250 genes cause inherited retinal degenerations with a high degree of genetic heterogeneity. New techniques in next-generation sequencing are allowing the comprehensive analysis of all retinal disease genes thus changing the approach to the molecular diagnosis of inherited retinal dystrophies. This review serves to analyze clinical progress in genetic diagnostic testing and implications for retinal gene therapy. METHODS: A literature search of PubMed and OMIM was conducted to relevant articles in inherited retinal dystrophies. RESULTS: Next-generation genetic sequencing allows the simultaneous analysis of all the approximately 250 genes that cause inherited retinal dystrophies. Reported diagnostic rates range are high and range from 51% to 57%. These new sequencing tools are highly accurate with sensitivities of 97.9% and specificities of 100%. Retinal gene therapy clinical trials are underway for multiple genes including RPE65, ABCA4, CHM, RS1, MYO7A, CNGA3, CNGB3, ND4, and MERTK for which a molecular diagnosis may be beneficial for patients. CONCLUSION: Comprehensive next-generation genetic sequencing of all retinal dystrophy genes is changing the paradigm for how retinal specialists perform genetic testing for inherited retinal degenerations. Not only are high diagnostic yields obtained, but mutations in genes with novel clinical phenotypes are also identified. In the era of retinal gene therapy clinical trials, identifying specific genetic defects will increasingly be of use to identify patients who may enroll in clinical studies and benefit from novel therapies.

Pediatric Pseudotumor Cerebri Syndrome.

Idiopathic intracranial hypertension, otherwise known as primary pseudotumor cerebri syndrome (PTCS), most frequently occurs in obese women of childbearing age. However, children may be affected as well. This review will address recent findings regarding demographics, diagnosis, and treatment of pediatric PTCS. Prepubertal children with primary PTCS have an equal sex distribution and less frequent obesity compared with adult patients. However, female gender and obesity are risk factors for primary PTCS in postpubertal children. Compared with adults, children with PTCS more frequently present with ocular motility deficits and more often have associated medical conditions that increase the risk of developing PTCS. Visual field testing may be unreliable, and the optimal modality to monitor visual function is unknown. MRI shows signs of elevated intracranial pressure (ICP) in children with PTCS similar to that of adults. It has now been established that elevated ICP in children ≤18 years old is greater than 25 cm H20 in nonobese, nonsedated children, and greater than 28 cm H2O in the remainder. Optical coherence tomography (OCT) may be used to distinguish pseudopapilledema from papilledema, monitor response to treatment in preverbal children, and identify patients with PTCS at risk for permanent visual loss. However, the precise role of OCT in the management of pediatric PTCS remains to be determined.

[Genome Editing Tools and their Application in Experimental Ophthalmology]. / Genome Editing Tools und ihr Einsatz in der experimentellen Augenheilkunde.

New genome editing tools in molecular biology are revolutionising precise genome surgery and have greatly influenced experimental ophthalmology too. Aside from the commonly used nuclease-based platforms, such as the zinc-finger nucleases (ZFN) and transcription activator-like effector nucleases (TALEN), CRISPR/Cas systems, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) genes, perform very efficiently in site-specific DNA cleavage within living cells. DNA double strand breaks (DSB) are repaired through two different conserved repair pathways: NHEJ (non-homologous end joining) and HDR (homology directed repair). By using the correct DNA templates, these repair pathways can be used to knock out defective genes or to repair mutations. Genome editing technology lays the ground for new strategies in basic science, biotechnology, and biomedical science, as well as clinical studies with genome editing. Therapeutic gene editing strategies are now concentrating on diseases in the retina, due to the comparatively easy accessibility of the eye and with local application in vivo.

[Gene Replacement Therapy for Inherited Retinal Dystrophies]. / Genersatztherapie bei hereditären Netzhauterkrankungen.

Characteristics of inherited retinal dystrophies include deficiencies in light perception and nervous conduction within the retina, leading to reduced vision or even blindness. In this context, the loss of function of photoreceptor-specific genes causes a variety of clinically and aetiologically distinct syndromes - each of them belonging to the group of rare diseases. With a prevalence of 1 in 2500, however, inherited retinal diseases are clinically significant and important - especially since these diseases lead to restrictions of a patient's fitness for work and overall quality of life. More than 250 genetic mutations causing the various types of inherited retinal dystrophies have been identified by now (https://sph.uth.tmc.edu/Retnet). In recent years, preclinical research on suitable animal models has yielded important progress in the understanding of the mutations underlying the pathological and molecular biological processes of these diseases. These findings have led to the development of novel and innovative therapeutic strategies for the treatment of inherited retinal dysfunctions, which are still incurable. Meanwhile, many of the successful preclinical studies have led to translational research projects aiming to find treatment options for human patients. However, some preliminary results of these human translational studies indicate the need to optimise and refine the underlying therapeutic concepts.

[Segregation Analysis in Inherited Eye Disorders: An Academic Add-on or An Essential Effort?] / Die Segregationsanalyse bei erblichen Augenerkrankungen ­ akademisches Extra oder notwendiger Aufwand?

The knowledge of the genetic basis of many eye diseases is constantly increasing. Besides retinal degeneration, developmental defects of the anterior segment, cataracts, and the development of the basic structure are often associated with genetic defects. Moreover, a lot of genetic syndromes involve eye abnormalities. The impact of genetics has become more and more evident in ophthalmological practice. Although genetic counselling is usually carried out by human geneticists, the increasing availability of therapeutic options requires ophthalmologists to have some basic knowledge of the genetic causes and how to identify them. The first step in this regard is to recognise potential genetic eye disorders and to initiate an adequate genetic analysis to confirm the diagnosis. This review discusses possible and necessary investigations within the patient's family facing ophthalmologists after the genetic cause of an eye disease has been identified.

[Diagnosis and Therapy of Iris Lesions]. / Diagnostik und Therapie von Irisläsionen.

The most common iris lesions are iris nevi, iris melanomas and iris pigment epithelium cysts. However, there is an abundance of rare differential diagnoses that have to be considered, including other melanocytic and non-melanocytic lesions. Diagnostic tools include the slit lamp examination, gonioscopy, tonometry, transillumination, ultrasound biomicroscopy (UBM), optical coherence tomography, fluorescein angiography and standardized photography-assisted documentation. The timely identification of malignant lesions (i.e. iris melanoma) is paramount. To assess malignancy criteria of iris nevi, the ABCDEF rule (age young, blood, clock hour inferior, diffuse growth, ektropion uveae, feathery margins) can be applied. Statistically, up to 11% of iris nevi may develop into iris melanomas within 20 years. TNM Staging follows the 2010 AJCC cancer staging manual and helps determine the optimal treatment strategy. Treatment options include radiotherapy, such as plaque brachytherapy and proton beam radiation therapy, as well as surgical excision. Both the surgical and the radiotherapeutic approaches show comparable local tumor control rates. However, the spectrum of therapy-related side effects and complications may differ amongst treatment modalities. After initial treatment, patients should be followed up every 3 - 6 months. Tumor-related mortality ranges between 0 - 11% and is significantly lower than in other uveal melanomas. A prognostic value of common genetic alterations, which have been identified as significant prognostic factors in posterior uveal melanoma, could not be shown for iris melanoma.

Guidance of Medical Care for Familial Exudative Vitreoretinopathy：Research on Rare and Intractable Diseases, Health and Labour Sciences Research Grants.

Familial exudative vitreoretinopathy is a hereditary insufficiency of retinal vascularture, which manifests a variety of vitreoretinal abnormalities, including nonvascularlized retina, abnormality of retinal vessel growing, dragged retina, retinal folds and total retinal detachment. While causative genes have been identified, cases are often sporadic. Periodic examination is necessary to find recurrence of the disease and late complications, including rhegmatogenous retinal detachment, cataract and glaucoma.

[The research advances and applications of genome editing in hereditary eye diseases].

Genome editing is a cutting-edge technology that generates DNA double strand breaks at the specific genomic DNA sequence through nuclease recognition and cleavage, and then achieves insertion, replacement, or deletion of the target gene via endogenous DNA repair mechanisms, such as non-homologous end joining, homology directed repair, and homologous recombination. So far, more than 600 human hereditary eye diseases and systemic hereditary diseases with ocular phenotypes have been found. However, most of these diseases are of incompletely elucidated pathogenesis and without effective therapies. Genome editing technology can precisely target and alter the genomes of animals, establish animal models of the hereditary diseases, and elucidate the relationship between the target gene and the disease phenotype, thereby providing a powerful approach to studying the pathogenic mechanisms underlying the hereditary eye diseases. In addition, correction of gene mutations by the genome editing brings a new hope to gene therapy for the hereditary eye diseases. This review introduces the molecular characteristics of 4 major enzymes used in the genome editing, including homing endonucleases, zinc finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR-associated protein 9 (Cas9), and summarizes the current applications of this technology in investigating the pathogenic mechanisms underlying the hereditary eye diseases. (Chin J Ophthalmol, 2017, 53: 386-371).