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     Vein occlusions are the second only to diabetes in producing disease of the vessels of the retina.  There are two basic types of vein occlusion, branch retinal vein occlusion (BRVO), in which one of the branches of the main vein are blocked, and central retinal vein occlusion (CRVO) in which the main vein of the eye is blocked.  Vein occlusions are associated with various illnesses including high blood pressure, glaucoma, arteriosclerosis, clotting problems, diabetes, and many other diseases.

     Vein occlusions occur at the junction of an artery and vein in the retina.  The artery is a relatively stiff vessel compared to the vein, which is very pliable.  At points where the artery and vein cross they are attached together by connective tissue.  If the artery develops arteriosclerosis (becomes stiff) or a high pressure in the artery occurs, it can actually block the vein.  When the vein is blocked, it cannot allow the blood being pumped into the eye by the arteries to leave the eye and the resultant high blood pressure in the system ruptures the small capillaries connecting the arteries and veins.  Bleeding occurs in the retina and the capillaries may be so damaged that they become leaky and serum leaks into the retina.  The retina is normally like a dry "sponge" of neurological tissue and this leakage causes it to swell or thicken like a wet sponge keeping the retina from working correctly.  When the retina, and particularly the macula (center of vision) is thickened from leaking fluid we call it macular edema.   Further, the damage to the retina can be so severe that it dies from lack of oxygen which we call "ischemia". 

     The complications of a BRVO or a CRVO are what you might expect from the damage done to the eye.  The most common cause of decreased vision is the leakage, macular edema.  In many patients this will clear on its own over time, however, if it doesn't in three months or more, laser or surgical therapy may be needed.  A second problem is the development of new vessels.   These grow not into the damaged retina where they are needed but into the vitreous cavity.  These vessels can bleed and partially or totally fill the vitreous cavity, blocking off vision.  Laser or vitrectomy surgery may be needed, but sometimes, based on the amount of bleeding, simply waiting and positioning of your head may help to clear vision.  Finally, a devastating complication, particularly for CRVOs, is the development of new vessels on the surface of the iris (see Anatomy) called rubeosis.  These vessels can block the outflow channels of the eye (trabecular meshwork) and cause a very hard to control glaucoma (neovascular glaucoma).  Patients are followed very closely for the first six months after a CRVO to watch for this problem.

    The Branch Vein Occlusion Study and the Central Vein Occlusion Study were performed to determine if and when laser photocoagulation was indicated in these diseases for macular edema and new vessels.  Laser was found to be advantageous over no treatment in the treatment of macular edema in BRVOs but not CRVOs and for specific indications with neovascularization (retinal and iris) in each disease.  Laser works (presumably) by causing leaking vessels to stop leaking and by decreasing the need for oxygen in damaged areas (thus decreasing the need for new vessels).  Laser does not, however, open the damaged vessels and return normal blood flow to the retina.

    Recently, the surgical treatment of BRVOs was reported.  After performing a vitrectomy the crossing artery and vein were surgically separated and opened the damaged veins with return of blood flow the affected area of the retina in the majority of cases with improvement in vision.  As a result of this paper, the Retinal Vascular Surgery-Branch Retinal Vein Occlusion Study was started with six centers around the country, including RVT.  We were the coordinating center for the entire study with Dr. Lambert as the director of the coordinating center and the center chairmen are Drs. Opremcak and Bruce in Columbus, Ohio.  Other study centers include Donald D'Amico, MD in Boston, Keye Wong, MD in Sarasota, Fl, Patrick Rubsamen, MD in Miami, Fl, and Edgar Thomas, MD in Los Angeles, CA.  We found a definite benefit to surgery, however newer injection techniques have supplanted surgery. New anti-VEGF meds (Avastin and Lucentis) and the use of intraocular steroids have helped in the treatment of these diseases. RVT is participating in the SCORE trial evaluating the use of intraocular Kenalog (steroid) in the early treatment of these problems.

Disclaimer Stuff: The opinions expressed in this website are those of RVT.  Diagnosis and therapy should be based on a thorough examination by and recommendations of a qualified eye provider.