The retina is the delicate light-sensitive membrane that lines the inside of the eye. Like the rest of the body, the retina has blood vessels that supply it with vital oxygen and nutrition. Arteries are the vessels carrying blood into the eye while veins carry blood out. The retinal arteries and veins criss-cross over each other at numerous locations in the retina. Rarely, at one of these crossing points, the thicker walled artery may compress the more fragile vein and lead to a partial obstruction. This is called a branch retinal vein occlusion (BRVO).
BRVOs are seen most commonly in patients whose blood vessel health is less than ideal. In these patients, atherosclerosis (hardening of the arteries) leads to a thickening of the wall of retinal arteries and makes it more likely that an artery will push on a vein leading to an obstruction. Factors that increase the risk for BRVO include high cholesterol, being overweight, and especially high blood pressure.
The most common cause of visual loss in patients with a BRVO is macular edema (swelling in the central retina). A backlog of pressure may build up in the retinal veins upstream from the obstruction site causing damage to the walls of the retinal veins. This in turn may cause bleeding or leakage of clear fluid (serum) into the retina causing it to swell. If this swelling affects the central retina, blurring of the vision will result.
There are currently three treatments that have been proven to be beneficial for patients with macular edema due to BRVO: Anti-VEGF drugs (eg. Avastin or Lucentis), Grid laser photocoagulation and an intraocular steroid implant (Ozurdex). Anti-VEGF drugs have been proven to reduce edema and improve vision in approximately 2/3 of patients with BRVO. These drugs are injected inside the eye in a painless in-office procedure which only takes a few minutes (see intravitreal injections). Most patients require numerous injections to dry up the swelling or maintain the effect. Injections are most commonly administered monthly as long as they offer a benefit. Grid laser treatment has also been proven to reduce edema in patients with BRVO but is only helpful for patients with normal blood flow to the central retina (perfused BRVO). Laser is also avoided if a significant amount of hemorrhage is present in the retina. Ozurdex is a small steroid pellet that can be injected inside the eye and has also been proven to reduce edema and improve vision in many patients with BRVO. The slow-release pellet can be effective for 4-6 months but can speed the development of cataract and cause a pressure rise inside the eye. While anti-VEGF drugs are usually the first line treatment, many patients benefit from a combination of these therapies.
A minority of patients with BRVO will develop the growth of abnormal blood vessels from the retina (neovascularization). Left alone, these blood vessels may bleed into the vitreous cavity (vitreous hemorrhage) which may reduce vision. Scatter laser treatment (different than grid laser) has been proven to reduce the risk of vitreous hemorrhage and is usually recommended for BRVO patients who develop neovascularization.
The Retina Care Center physicians have extensive experience treating patients with branch retinal vein occlusions and utilize the full spectrum of diagnostic and treatment tools available. We are also actively involved in research and are currently enrolling interested patients into a national multicenter study investigating the benefits of a new anti-VEGF drug, Eylea for patients with BRVO.