Branch retinal vein occlusion occurs when part of the venous drainage system of the retina is blocked. Blood flows through retinal arterioles, capillaries and finally through branch retinal veins that drain into the central retinal vein. A blockage in one of these branch retinal veins causes backpressure and leads to hemorrhage, exudation, and/or decreased blood flow in the area of the retina drained by that particular branch retinal vein.
Branch retinal vein occlusions are by far the most common cause of retinal vascular occlusive disease. Males and females are affected equally. Most occlusions occur after age 50, although younger patients are sometimes seen with this disorder (in this age group it is often called (papillophlebitis). The highest rate of occurrence is in individuals in their 60’s and 70’s. These disorders are similar to those for vascular occlusive disease elsewhere in the body such as stroke and coronary artery disease. Specifically, aging, high blood pressure, diabetes, and smoking are all risk factors.