Branch Vein Occlusions
To understand branch vein occlusions, it's helpful to know a little bit about the retina. The retina is a delicate, light—sensing tissue in the back of the eye. It Is very dependent upon a rich supply of nutrients to meet its high rate of metabolism and receives these nutrients by removing then from the blood via a system of fine blood vessels. These blood vessels are visible with a variety of instruments in the office and we can make very specific diagnoses of disease as they occur within the structure of the vessels. A permanent record of these changes is sometimes desirable; this can be done by taking photographs of the back of the eye.
One of the most common diseases to affect these fine retinal vessels is an obstruction of a small branch retinal vein. The arteries and the veins run together and sometimes cross over each other. At these intersections are frequent trouble spots. A thickened artery may compress the vein enough to block the flow and result in a B.V.O. With it come hemorrhages, swelling and lack of function in the affected cells of the retina. These changes result in blurred vision which is sometimes temporary, sometimes permanent.
What causes Branch Vein Occlusions?
Seventy five percent of patients with B.V.O. have high blood pressure. Other diseases which predispose to this condition are diabetes, diffuse hardening of the arteries and other blood diseases.
About 30% of patients recover completely with little trace that the B.V.O. ever happened. The other 70% have persistent visual problems. Every case is different.
The threats to vision take two basic forms: 1. Macular edema, due to persistent swelling from the damaged vessels and, 2. Neovascularization, which is the growth of new, abnormal blood vessel networks. These nets are fragile and tend to leak fluid and blood, thereby causing blurred vision.
Some improve during the first few weeks to months. Many cases get better on their own, simple observation is appropriate at first. Photographs are helpful in following the course of the disease. If either of the two previously mentioned threats to vision are present, laser therapy may be indicated to close the leaking capillaries or destroy the new blood vessels. No medicines have proven to be of any benefit.