Inwardly rectifying K⁺ channel expressed at high levels in retinal pigment epithelium (RPE), choroid plexus, and kidney. Maintains ionic and fluid homeostasis across the RPE basal membrane, supporting photoreceptor viability. KCNJ13 loss-of-function mutations cause Leber congenital amaurosis 16 (LCA16) and snowflake vitreoretinal degeneration (SVD), both rare autosomal recessive retinal dystrophies with childhood onset.