I've been diagnosed with retinal branch vein occlusion with edema in my left eye. No one at my HMO can give me an answer as to why this happened. I do not have high blood pressure or diabetes. It is so frightening to become blind in one eye. What can I do to prevent my other eye from doing the same thing?

Marilyn

The retina is nourished by four main branches of blood vessels, each of which supports one-quarter of the retina. The retinal arteries supply blood and nutrients, while the retinal veins whisk blood and waste away from the retina.

If one of the retinal vein branches becomes blocked, serious consequences to vision can occur. When a branch retinal vein becomes obstructed, the corresponding branch retinal artery is still able to supply the retina with blood and nutrients, but these materials do not drain properly. This situation results in the spilling of blood, fluid and nutrients into the retina. When fluid accumulates in the retina (retinal edema), it can cause loss of vision. If this is detected early enough, a retinal specialist can generally treat the swollen area with a laser -- a procedure that has been shown to improve vision in a majority of patients. (A similar type of vision disorder, called central vein occlusion, involves the large vein that collects blood from all four branch retinal veins.)

As you mention, risk factors for a blockage of a branch retinal vein include high blood pressure, diabetes, atherosclerosis and glaucoma. Also, people over the age of 50 are at higher risk of developing this problem than younger people. To answer your specific question, people without any known risk factors do occasionally get branch retinal vein occlusion. Further research is under way, but it may be many years before we identify all the factors that contribute to branch retinal vein occlusion. So, right now, the best preventive strategy is to keep a close watch on your blood pressure, blood sugar, cholesterol and eye pressure. In the meantime, if you are dissatisfied with the care you are receiving, you should try to get a second opinion from another retinal specialist. A second opinion may be very helpful in your case because there may be a possibility that laser treatment could restore some of the vision that you have lost from the branch retinal vein occlusion.