The function of blood cells is to deliver oxygen to our tissues such as muscle, skin, brain and our eyes so that they can function properly. So when blood flow is blocked the tissue in question begins to malfunction. In the case of a retinal vein occlusion, there is blockage of a vein leading to a lack of blood flow to the retina and eventually damage resulting in poor vision. When the main retinal vein is blocked it is called a central retinal vein occlusion (CRVO). Like any large river there are tributaries and when one of these is blocked it is called a branch retinal vein occlusion (BRVO). If either retinal vein becomes blocked, pressure begins to build up as in any plumbing system, resulting in retinal hemorrhages, leakage and swelling of the retina called macular edema.
It is not known definitively what causes a retinal vein occlusion but there are certain risk factors including high blood pressure, diabetes, vascular disease and glaucoma (CRVO).
CRVO almost always occurs in one eye but when it is present in both eyes we worry about diseases that cause a general “thickening” of the blood as these conditions can lead to blood clots. In such cases we recommend more extensive blood testing, evaluation by your PCP and possibly referral to a hematologist.
There is no cure for retinal vein occlusions because current medical technology cannot remove or dissolve the blockage. We do however have a number of medications that are injected into the eye to treat the vision threatening effects of retinal vein occlusion (see Anti-VEGF medications). Laser used to be the mainstay of treatment for this condition, but it is now reserved for only special circumstances.