Mizuo phenomenon in X-linked retinoschisis. Pathogenesis of the Mizuo phenomenon

• Four unrelated males with X-linked retinoschisis and a golden fundus reflex had Mizuo-Nakamura phenomenon, which, to our knowledge, has been described only in Oguchi's disease and X-linked cone dystrophy. These findings, together with experimental observations and data from the literature, led us to hypothesize that the Mizuo-Nakamura phenomenon is caused by an excess of extracellular potassium in the retina as a result of a decreased potassium scavenging capacity of retinal Muller cells.