Comprehensive Genotyping and Phenotyping Analysis of GUCY2D-Associated Rod- and Cone-Dominated Dystrophies

Monogenic Retinal Diseases Associated With Genes Encoding Phototransduction Proteins: A Review

Phototransduction, the process by which captured photons elicit electrical changes in retinal rod and cone cells, represents the first neuronal step in vision and involves interactions between several highly specialised proteins. Pathogenic variants in genes encoding many of these proteins can give rise to significant vision impairment, accounting for a substantial portion of inherited retinal disease. Such genes include RHO, OPN1LW, OPN1MW, GNAT1, GNAT2, GNB3, PDE6A, PDE6B, PDE6G, PDE6C, PDE6H, CNGA1, CNGB1, CNGA3, CNGB3, GRK1, SAG, ARR3, RGS9, RGS9BP, GUCY2D, GUCA1A and SLC24A1. Many of these conditions have distinct mechanisms and clinical features. They follow several modes of inheritance (including in one case digenic, or tri-allelic, inheritance). Some conditions also entail myopia. Rod and cone phototransduction will be outlined, followed by the discussion of diseases associated with these genes. Some phenotypic features will be highlighted as well as their prevalence in a large genotyped inherited retinal disease cohort.

Progression of retinitis pigmentosa on static perimetry, optical coherence tomography, and fundus autofluorescence

In retinitis pigmentosa (RP), photoreceptor degeneration leads to progressive visual field loss and visual impairment. Several therapeutic trials are ongoing aiming to establish effective treatments. Although functional evaluations are commonly used in clinical trials, residual ellipsoid zone (EZ) measurement on optical coherence tomography has been shown to be more sensitive to detect disease progression. Establishment of sensitive outcome measurement is essential to develop new therapeutic strategies. In the current study, we evaluated the progression rates of the disease in 76 eyes of 76 patients with RP, using the residual EZ length, ring-shaped macular hyperautofluorescent (AF), and visual field. Decrease rates measured by the residual EZ area and by the hyper-AF ring area were strongly positively correlated (P < 0.0001, r = 0.71). The reduction rates of the residual EZ length and hyper-AF ring radius were constant regardless of their baseline measurements. Faster annual reduction rates of the hyper-AF ring area or radius were significantly correlated with faster visual field progression (P = 0.03, r = 0.25 and P = 0.004, r = 0.33, respectively). These findings support the usage of morphological measurements such as EZ or hyper-AF ring measurements as outcome measurement for future clinical trials for RP.

Occult Macular Dysfunction Syndrome: Identification of Multiple Pathologies in a Clinical Spectrum of Macular Dysfunction with Normal Fundus in East Asian Patients: EAOMD Report No. 5

Occult macular dystrophy (OMD) is the most prevalent form of macular dystrophy in East Asia. Beyond RP1L1, causative genes and mechanisms remain largely uncharacterised. This study aimed to delineate the clinical and genetic characteristics of OMD syndrome (OMDS). Patients clinically diagnosed with OMDS in Japan, South Korea, and China were enrolled. The inclusion criteria were as follows: (1) macular dysfunction and (2) normal fundus appearance. Comprehensive clinical evaluation and genetic assessment were performed to identify the disease-causing variants. Clinical parameters were compared among the genotype groups. Seventy-two patients with OMDS from fifty families were included. The causative genes were RP1L1 in forty-seven patients from thirty families (30/50, 60.0%), CRX in two patients from one family (1/50, 2.0%), GUCY2D in two patients from two families (2/50, 4.0%), and no genes were identified in twenty-one patients from seventeen families (17/50, 34.0%). Different severities were observed in terms of disease onset and the prognosis of visual acuity reduction. This multicentre large cohort study furthers our understanding of the phenotypic and genotypic spectra of patients with macular dystrophy and normal fundus. Evidently, OMDS encompasses multiple Mendelian retinal disorders, each representing unique pathologies that dictate their respective severity and prognostic patterns.