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retinoschisis occurring before 10 years of age and within the nerve-fiber layer, with frequent macular involvement; at first, the inner wall is a translucent veillike membrane, but it becomes denser and may render the retina white; autosomal recessive inheritance. There is a form of this condition in middle age that is X linked [MIM*312700] and a rare autosomal dominant form [MIM*180270].
A vitreoretinal degeneration characterized by splitting of the retina into two layers. It occurs either as a hereditary disease or as an acquired condition (70% of these patients are hyperopic). The X-linked hereditary condition (called juvenile retinoschisis) affects only males and usually involves the macula with loss of central vision. The congenital condition is characterized by a splitting of the nerve fibre layer from the retina whereas the acquired form, which is the most common, results in a splitting at the outer plexiform layer. The latter usually begins in the temporal periphery appearing as a coalescence of microcystoid degenerations with a smooth transparent elevation and associated with an absolute scotoma. The condition may spread to involve the entire peripheral fundus. Holes in the two layers are common and are a sign of progression. The inner layer contains blood vessels and sometimes has small whitish flakes on it, which are called 'snowflakes'.