Retinal Venous Occlusion
Retinal vein occlusion is second only to diabetic retinopathy as a cause of vision loss due to disease affecting the blood circulation of the retina. There are two types: branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO).
Branch Retinal Vein Occlusion
A BRVO is a blockage of one of the veins that drains blood from the retina. Arteries carry blood to the retina. Red blood cells and plasma fluid then travel through even smaller blood vessels called capillaries and ultimately into the venous system starting with small veins feeding into larger veins and finally reaching the central retinal vein. When there is a blockage in any vein, there is back-up pressure within the capillaries leading to retinal swelling due to fluid leakage into the retina. Both males and females can develop BRVO. Most commonly BRVO develops after the age of 50, although young patients can also experience this disease. BRVO is the leading cause of retinal vascular occlusive disease. High rates of occurrence are seen among patients in their 60’s and 70’s.
Risk factors for BRVO include atherosclerotic risk factors or manifestations, such as coronary artery disease, stroke, high blood pressure, diabetes, and smoking. Glaucoma is also a risk factor. Less common conditions that can cause BRVO include blood clotting abnormalities and inflammatory and infectious illnesses, such as sarcoidosis, vasculitis, and tuberculosis. These are more common in younger patients who do not have the previously mentioned risk factors.
Complications of BRVO include: macular edema, macular ischemia, and neovascularization (formation of new abnormal blood vessels), somewhat similar to what can be seen in diabetic retinopathy.
Leaking in the macula causes macular edema or swelling. The macula is responsible for central vision and it does not function as it should when it is swollen. Symptoms of macular edema include blurry vision and loss of portions of the field of vision. As in diabetic macular edema, we recommend anti-angiogenic treatment with Lucentis, Eylea or Avastin (Lucentis and Eylea are more effective). Laser photocoagulation treatment may be effective in stabilizing and improving vision in selected cases.
Central Retinal Vein Occlusion
CRVO is the obstruction of the final retinal vein, which is located at the optic nerve. Since blood flow out of the retina is limited, fluid accumulates in the retina and it becomes swollen. If there is a partial blockage, the retina may continue to function as normal. A severe blockage can permanently damage the retina and cause vision loss.
Risk factors for CRVO include coronary artery disease, stroke, high blood pressure, diabetes, and smoking. Glaucoma is also a risk factor. Less common conditions that can cause CRVO include blood clotting abnormalities and inflammatory and infectious illnesses.
CRVO can be categorized as non-ischemic and ischemic. In some instances there is a significant obstruction of capillaries. This can cause an abnormal type of neovascularization that develops in front of the iris, effectively obstructing the outflow path for the fluid that is constantly being produced in the eye to maintain a certain pressure within the eye. Patients with this condition can experience neovascular glaucoma, which is characterized by high pressure in the eye to a level that is damaging to the optic nerve. This complication is very serious and may cause severe vision loss, pain, or loss of the affected eye. A combination of anti-angiogenic injections: Lucentis, or Eylea and occasionally laser photocoagulation may prevent these complications. Avastin is safe but less effective than Lucentis or Eylea
As with BRVO, patients with CRVO may also experience macular edema and macular ischemia. Laser photocoagulation has not been proven effective in treating macular edema, particularly among elderly patients. However, anti-angiogenic drugs, such as Lucentis or Eylea, are effective in most cases, and this has become the mainstay of treatment. Avastin is safe but less effective than Lucentis or Eylea. Some patients with CRVO may benefit from localized laser treatment of macular edema. Intraocular steroids may be helpful in non-responsive cases, although they carry a risk of glaucoma.