Cystoid degeneration of the peripheral retina (Blessig's cysts, Iwanoff's retinal edema) is observed so commonly that it has been regarded as a normal consequence of growth and aging.1-6 Closely related to this Blessig-Iwanoff cyst formation throughout the peripheral retina, particularly on the temporal side, is a more extensive type of retinal degeneration called retinoschisis. In this condition the typical Blessig-Iwanoff microcysts fuse and spread both circumferentially and posteriorly, splitting the retina into two leaves. The clinical literature pertaining to retinoschisis has recently been reviewed by Shea, Schepens, and Pirquet,7 and the general features of the pathologic anatomy of retinoschisis have been described by Samuels and Fuchs,5 Teng and Katzin,6 and by Francois and Rabaey.8 It is the purpose of this paper to review the pathologic anatomy of retinoschisis, attempting to establish an anatomical basis for some of the more recently appreciated ophthalmoscopic characteristics of retinoschisis, and