Branch Retinal Vein Occlusion
A branch retinal vein occlusion is essentially a blockage of the portion of the circulation that drains the retina of blood. The arteries deliver blood to the retina. The red blood cells and plasma then course through the capillaries and eventually into the venous system, beginning with small veins and ending with larger ones, and eventually reaching the central retinal vein. With blockage of any vein, there is back-up pressure in the capillaries, which leads to hemorrhages and also to leakage of fluid and other constituents of blood. Usually, the occlusion occurs at a site where an artery and vein cross. The occlusion site determines the extent or distribution of the hemorrhage, ranging from a small vein branch to a quadrantic occlusion involving one fourth of the retina to a hemispheric (hemi-retinal) occlusion involving one half of the retina to an occlusion of the central retinal vein, which involves the entire retina (when the central vein is involved, this is called a central retinal vein occlusion).
Related conditions: Retinal Vein Occlusion,