Characteristics of the hemispheric retinal vein occlusion.

Hemispheric retinal vein occlusions involve the venous return from approximately one-half of the retina and have characteristics of both central retinal vein occlusions and branch retinal vein occlusions. One hundred six such occlusions were studied in 104 patients whose average age was 66 years. The site of the hemispheric vein occlusion was located in a branch retinal vein in 90% of the eyes, and in 10% of the eyes it was located in one of the dual intraneural trunks of the central retinal vein. Of these eyes, 11% developed neovascularization of the disc, 9% developed neovascularization of the retina elsewhere, 9% developed neovascularization of the iris, and 3% developed neovascular glaucoma. Neovascularization was positively correlated with an increasing percentage of capillary nonperfusion (ischemic index) within the area of occlusion. Prophylactic argon laser treatment was effective in reducing the incidence of neovascularization in eyes with significant capillary nonperfusion.