Histopathologic study of nine branch retinal vein occlusions.

Occlusions of nine branch retinal veins in eight eyes of seven patients were studied histopathologically by serial sections through the affected areas. Intravitreal neovascularization from the disc, retina, or both was noted in four eyes. Two additional eyes had intraretinal neovascularization (intraretinal microvascular abnormalities). Cystoid macular edema was present in five eyes. A fresh or recanalized thrombus was noted at the site of vein occlusion in all eyes. Inner ischemic atrophy of the retina was found distal to the area of occlusion in six of the nine affected quadrants of the eight eyes. Although the corresponding branch retinal arteries showed varying degrees of sclerosis (severe, three eyes; moderate, five eyes; and minimal, one eye), no definite thrombus was observed in any of them.