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      Clinical Findings in Four Siblings with Genetically Proven Oguchi Disease

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          Abstract

          Purpose:

          To assess the clinical findings in normal daylight status and 3 h of dark-adapted status in family members with Oguchi disease (OD).

          Methods:

          Four siblings with OD and their parents were included in this case series. The presence of disease was confirmed with genetic analysis and comprehensive clinical evaluation. Corrected distant visual acuity (CDVA), automated visual field analysis (VFA), optical coherence tomography (OCT), OCT angiography (OCTA), colored fundus photography, fundus autofluorescence (FAF), fundus fluorescein angiography (FFA), electroretinography (ERG), and dark adaptation test (DAT) results were obtained in normal daylight status. On the next day, after 3 h of dark adaptation, the patients were re-evaluated. The findings obtained in normal daylight status and 3 h dark-adapted status were compared.

          Results:

          The mean age of the four sibling subjects was 15.25 ± 2.2 years. All subjects had 20/20 CDVA and normal VFA. There was no abnormality in OCT and OCTA in normal daylight status and 3 h of dark-adapted status. Colored fundus photographs showed characteristic golden-yellow colored reflex in the mid-peripheral retina in normal daylight status, and discoloration in 3 h of dark-adapted status. In FAF and FFA, no abnormal pattern was observed in normal daylight status and 3 h of dark-adapted status. ERG showed rod function alterations and normal cone function. DAT showed delayed rod adaptation and normal cone adaptation. ERG and DAT findings remained unchanged after 3 h of dark adaptation.

          Conclusion:

          After 3 h of dark adaptation, golden-yellow fundus color returns to normal in patients with OD; however, rod function alterations and normal cone function in ERG, as well as delayed rod adaptation and normal cone adaptation in DAT remain unchanged.

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          Most cited references20

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          Congenital stationary night blindness: an analysis and update of genotype-phenotype correlations and pathogenic mechanisms.

          Congenital stationary night blindness (CSNB) refers to a group of genetically and clinically heterogeneous retinal disorders. Seventeen different genes with more than 360 different mutations and more than 670 affected alleles have been associated with CSNB, including genes coding for proteins of the phototransduction cascade, those important for signal transmission from the photoreceptors to the bipolar cells or genes involved in retinoid recycling in the retinal pigment epithelium. This article describes the phenotypic characteristics of different forms of CSNB that are necessary for accurate diagnosis and to direct and improve genetic testing. An overview of classical and recent methods used to identify specific CSNB genotypes is provided and a meta-analysis of all previously published and novel data is performed to determine the prevalence of disease-causing mutations. Studies of the underlying molecular pathogenic mechanisms based on cell culture techniques and animal studies are outlined. The article highlights how the study of CSNB has increased understanding of the mechanisms of visual signalling in the retina, likely to prove important in developing future treatments for CSNB and other retinal disorders.
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            Molecular genetics of Oguchi disease, fundus albipunctatus, and other forms of stationary night blindness: LVII Edward Jackson Memorial Lecture.

            To compare the clinical findings of the various forms of stationary night blindness caused by mutations in identified genes encoding proteins of photoreceptors or the retinal pigment epithelium. Review of the visual acuities, visual fields, fundi, dark-adaptation curves, and electroretinograms from patients with stationary night blindness caused by mutations in the genes RHO, GNAT1, PDE6B, RHOK, SAG, RDH5, and CACNA1F, respectively encoding rhodopsin, the alpha subunit of rod transducin, the beta subunit of rod cGMP-phosphodiesterase, rhodopsin kinase, arrestin, 11-cis retinol dehydrogenase, and a retinal L-type calcium channel. In the evaluated forms of stationary night blindness, the time course of dark adaptation and the characteristics of the electroretinogram indicate that rod photoreceptors are present and that they function, although abnormally. In night blindness resulting from defects in rhodopsin, the alpha subunit of rod transducin, or the beta subunit of rod cGMP phosphodiesterase, rod photoreceptors respond only to light intensities far brighter than normal, and the sensitivity of rods to light is similar to that of normal individuals who are not dark adapted. In fundus albipunctatus and in Oguchi disease, the rod photoreceptors can achieve normal sensitivity to dim light but only after 2 or more hours of dark adaptation, compared with approximately 0.5 hours for normal individuals. In each of these forms of stationary night blindness, the poor rod sensitivity and the time course of dark adaptation correlate with the known or presumed physiologic abnormalities caused by the identified gene defects. Patients with some forms of stationary night blindness, such as fundus albipunctatus and Oguchi disease, may develop degeneration of the retina leading to severe loss of vision in later life. The identification of the mutant genes causing forms of stationary night blindness refines the classification of these diseases and enhances our understanding of the underlying physiologic defects. Ophthalmologists must be aware that although these diseases are traditionally categorized as "stationary," some of them lead to reduced visual acuity or constricted visual fields, especially in older patients. Efforts to develop therapies for these diseases should concentrate on these more severe forms.
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              Assessing retinal structure in complete congenital stationary night blindness and Oguchi disease.

              To examine retinal structure and changes in photoreceptor intensity after dark adaptation in patients with complete congenital stationary night blindness and Oguchi disease. Prospective, observational case series. We recruited 3 patients with complete congenital stationary night blindness caused by mutations in GRM6, 2 brothers with Oguchi disease caused by mutations in GRK1, and 1 normal control. Retinal thickness was measured from optical coherence tomography images. Integrity of the rod and cone mosaic was assessed using adaptive optics scanning light ophthalmoscopy. We imaged 5 of the patients after a period of dark adaptation and examined layer reflectivity on optical coherence tomography in a patient with Oguchi disease under light- and dark-adapted conditions. Retinal thickness was reduced in the parafoveal region in patients with GRM6 mutations as a result of decreased thickness of the inner retinal layers. All patients had normal photoreceptor density at all locations analyzed. On removal from dark adaptation, the intensity of the rods (but not cones) in the patients with Oguchi disease gradually and significantly increased. In 1 Oguchi disease patient, the outer segment layer contrast on optical coherence tomography was 4-fold higher under dark-adapted versus light-adapted conditions. The selective thinning of the inner retinal layers in patients with GRM6 mutations suggests either reduced bipolar or ganglion cell numbers or altered synaptic structure in the inner retina. Our finding that rods, but not cones, change intensity after dark adaptation suggests that fundus changes in Oguchi disease are the result of changes within the rods as opposed to changes at a different retinal locus. Copyright © 2012 Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                J Curr Ophthalmol
                J Curr Ophthalmol
                JCO
                Journal of Current Ophthalmology
                Wolters Kluwer - Medknow (India )
                2452-2325
                Oct-Dec 2020
                12 December 2020
                : 32
                : 4
                : 390-394
                Affiliations
                [1 ]Department of Ophthalmology, Hatay State Hospital, Hatay, Turkey
                [2 ]Department of Ophthalmology, Ankara Ulucanlar Eye Education and Research Hospital, University of Health Sciences, Ankara, Turkey
                Author notes
                Address for correspondence: Cagri Ilhan, Merkez Mah, Tayfur Sokmen Cad. No: 36, Antakya 31080, Hatay, Turkey. E-mail: cagriilhan@ 123456yahoo.com
                Article
                JCO-32-390
                10.4103/JOCO.JOCO_155_20
                7861099
                33553842
                3dadd2e4-33b5-44a4-95e2-9afab4aa09b8
                Copyright: © 2020 Journal of Current Ophthalmology

                This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.

                History
                : 19 April 2020
                : 29 July 2020
                : 04 August 2020
                Categories
                Original Article

                dark adaptation,electroretinography,fundus,mutation,oguchi disease

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