The basis for many of the ocular complications likely begins with incomplete development of the retinal vasculature. Resulting retinal ischemia leads to neovascularization, vitreous hemorrhage and traction, and retinal folds with some 20% going on to develop rhegmatogenous or traction detachments. There is, however, considerable clinical variability, even within families, with some infants blind from birth whereas some (41%) adults have only areas of remaining avascularity or evidence of macular dragging. In fact, some affected individuals are asymptomatic and diagnosed only as part of extensive family studies. Intraretinal lipid is often seen. Considerable asymmetry in the two eyes is common. Secondary cataracts often occur and phthisis bulbi results in some patients. The clinical picture is sometimes confused with retinopathy of prematurity.