Branch Retinal Vein Occlusion: second most common retinal vascular entity after diabetic retinopathy; equally affects males and females; increased incidence with hypertension, cardiovascular disease, and glaucoma. Anatomically, the superotemporal veins are most affected. Clinically, the patient presents with sudden visual field loss affecting the involved area. The prognosis for good vision depends on the extent of involvement, associated macular edema, and retinal vascular changes. Diagnosis is usually by fundus exam and can be potentiated by fluorescein angiography. Fundus exam shows superficial hemorrhages, retinal edema, and soft exudates as well as engorgement of the vein peripheral to the site of occlusion. Fluorescein angiography in the chronic phase shows presence of collaterals, microaneurysms and large areas of capillary loss, macular edema, occasional neovascularization , and serous detachment of the retina. Treatment options include observation and laser photocoagulation (argon grid pattern) for eyes having macular edema and vision less than 20/40.

Central Retinal Vein Occlusion: patients usually present with painless loss of vision and are found to have diffuse retinal hemorrhages in all four quadrants of the retina as well as dilated, tortuous veins. cotton-wool spots, disc edema , optociliary shunt vessels and neovessels might also be present. Multiple etiologies should be considered including: hypertension, glaucoma, optic disc edema, hypercoagulable states, vasculitis, drug-induced, and retrobulbar compression by tumors or grave's opthalmopathy. CRVO can be divided into ischemic and nonischemic variants (depending on risk for development of neovessels secondary to retinal ischemia). This division is important because prophylactic PRP should be considered in ischemic CRVO if follow-up cannot be assured. The distinction can be based on: presence of an APD, visual field defects, poor visual acuity, and fluorescein angiography showing capillary drop-out.

CRVO