Congenital Stationary Night Blindness and Ocular Genetic Testing

Congenital stationary night blindness (CSNB) is a rare group of genetically inherited retinal disorders that are present from birth and do not show progressive characteristics. It is typically accompanied by symptoms such as night blindness, photophobia, myopia, nystagmus, and strabismus. CSNB is classified into subtypes based on different electrophysiological findings and inheritance patterns. Cases with a normal fundus appearance are categorized into Riggs type and Schubert-Bornschein type (which includes complete and incomplete subtypes) based on electroretinographic findings, while abnormal fundus appearance characterizes forms such as fundus albipunctatus (FA) and Oguchi disease. The genetic variations responsible for CSNB differ according to its subtypes. Riggs type CSNB is commonly associated with mutations in the PDE6B, RHO, GNAT1, and SLC24A1 genes. Complete CSNB is linked to mutations in GRM6, TRPM1, GPR179, LRIT3, and NYX genes, whereas incomplete CSNB involves mutations in CABP4, CACNA2D4, and CACNA1F. In FA, which presents with an abnormal fundus, mutations are often found in the RDH5, RLBP1, RPE65, and LRAT genes. Oguchi disease is associated with mutations in the SAG and GRK1 genes. Most of these genes are related to retinal photoreceptors, bipolar cells, or proteins involved in the retinoid cycle and play roles in signal transmission or the visual cycle.