Venous Occlusive Disease
You or someone you know may have been diagnosed with a retinal vein occlusion. We have prepared the following explanation to help you understand this condition better.
What is a retinal vein occlusion?
The retina requires a rich blood supply. Arteries carry oxygenated blood from the heart to the retina and veins carry deoxygenated blood from the retina back to the heart via the optic nerve. The retinal arteries may thicken and become stiff with age, especially in persons with high blood pressure, elevated cholesterol/triglycerides or diabetes. The retinal arteries and veins are in close proximity within the optic nerve and cross at multiple locations on the surface of the retina. Thickening of the arteries can compress the retinal vein either in the optic nerve or where the arteries cross the veins. Sometimes the arteries compress the veins so much that the blood flow in the vein is interrupted and cannot flow back to the heart. This causes blood to back up in the retina much like water backs up in a bathtub with a clogged drain. The increased pressure of blood in the veins causes bleeding and swelling in the retina. There are three variations of retinal vein occlusions. The most common is a branch retinal vein occlusion where a retinal vein is blocked on the surface of the retina. The resultant hemorrhaging and swelling can cause decreased vision if the center of the retina (the macula) is involved. The second most common is a central retinal vein occlusion where the retinal vein becomes blocked within the optic nerve. Central retinal vein occlusions are typically more severe and causing hemorrhages and swelling throughout the retina leading to a more profound decrease in vision. The least common venous occlusion is a hemi-retinal vein occlusion where the vein draining one-half of the venous circulation is occluded. This is typically less severe than a central retinal vein occlusion but worse than a branch retinal vein occlusion.
What are symptoms of a retinal vein occlusion?
People who develop a retinal vein occlusion typically have the sudden onset of blurred vision in one eye (there are many other ocular conditions which cause the sudden onset of blurred vision so an examination is needed to determine the cause). Some retinal vein occlusions have no symptoms.
Treatment of retinal vein occlusions
There a number of treatments which may help the vision in eyes with retinal vein occlusions. Laser photocoagulation for macular edema (swelling) may stabilize or improve vision. The injection of anti-VEGF drugs (anti-vascular endothelial growth factors such as ranibizumab, bevacizumab or aflibercept) into the vitreous gel may also be used to treat macular edema associated with venous occlusive disease. Some eyes with venous occlusive disease develop the growth of abnormal, fragile blood vessels on the surface of the retina which can cause bleeding into the vitreous gel. Vitreous bleeding is usually associated with the sudden onset of floaters in the vision. Eyes with central retinal vein occlusions may also develop abnormal blood vessels on the iris which can cause a very severe form of glaucoma called neovascular glaucoma. Both neovascularization of the retina and iris are treated with scatter laser photocoagulation to the retina in the office. Retinal vein occlusions typically occur in only one eye so fortunately the vision in the fellow eye is unaffected. Since retinal vein occlusions are associated with hypertension, elevated cholesterol/triglycerides and diabetes, control of these medical conditions make venous occlusive disease less common.