BRANCH RETINAL VEIN OCCLUSION: Epidemiology, Pathogenesis, Risk Factors, Clinical Features, Diagnosis, and Complications. An Update of the Literature

Abstract

BACKGROUND/PURPOSE: Retinal vein occlusion is the second most common retinal vascular disorder after diabetic retinopathy and is considered to be an important cause of visual loss. In this review, the purpose is to make an update of the literature about the classification, epidemiology, pathogenesis, risk factors, clinical features, and complications of branch retinal vein occlusion (BRVO). METHODS: Eligible articles were identified using a comprehensive literature search of MEDLINE, using the terms "branch retinal vein occlusion," "pathogenesis," "epidemiology," "risk factors," "clinical features," "diagnosis," and "complications." Additional articles were also selected from reference lists of articles identified by the electronic database search. RESULTS: Classification, epidemiology, pathogenesis, risk factors, clinical features, and complications are analyzed. CONCLUSIONS: Branch retinal vein occlusion has an incidence of 0.5% to 1.2%. Several risk factors, such as hypertension, hyperlipidemia, diabetes mellitus, thrombophilia and hypercoagulation, systemic and inflammatory diseases, medications, and ocular conditions, have found to be associated with BRVO. The symptoms depended on the site and severity of the occlusion. The average reduction in visual acuity for ischemic BRVO is 20/50 and for nonischemic BRVO is 20/60. Acute BRVO can be detected by fundoscopy, where flame hemorrhages, dot and blot hemorrhages, cotton wool spots, hard exudates, retinal edema, and dilated tortuous veins can be observed. Chronic BRVO would be more subtle and characterized by the appearance of venous collateral formation and vascular sheathing, in addition to complications previously mentioned. Areas of ischemia can be evaluated using fluorescein angiography. The extent of macular edema and the presence of retinal detachment can be detected by fundoscopic examination or fluorescein angiography, although optical coherence tomography is considered to be the best method. As far as complications, the most common is macular edema, followed by retinal neovascularization, vitreous hemorrhage, or retinal detachment.