ABSTRACT
The ophthalmoscopic findings of an acute branch retinal vein occlusion (BRVO) include superficial flame-shaped hemorrhages, retinal edema, and often cottonwool spots in a sector of the retina. The occluded vein is dilated and tortuous, and with time the corresponding artery may narrow and become sheathed. The obstruction is caused by thrombosis at the arteriovenous crossing where the artery and vein share a common wall. The Branch Vein Occlusion Study Group found that 31% of untreated eyes with greater than 5 disc diameters of nonperfusion developed neovascularization. Surgical separation of the retinal vein and artery at the site of arteriovenous crossing by sectioning the common adventitial sheath with microsurgical techniques has been demonstrated in animals, cadaver eyes, and one patient with BRVO. Central retinal vein occlusion is most commonly caused by thrombus formation in the central retinal vein at the level of the lamina cribrosa, where the central retinal artery and vein share a common adventitial sheath.
