Branch retinal vein occlusion (BRVO)
Arteries are blood vessels that carry oxygenated blood from the heart to all parts of the body, including the retina. Veins are blood vessels that carry deoxygenated blood from all parts of the body back to the heart. Branch retinal vein occlusion is the blockage of a vein by a clot at the site where the artery and vein cross paths.
In about 50% of patients, branch retinal vein occlusion is related to hypertension-induced arteriosclerosis (that is, the narrowing and hardening of the arteries). Arteriosclerosis often affects people who are in their 50s and 60s in age.
During a retinal examination, there are several clinical signs the physician may detect that support a diagnosis of branch retinal vein occlusion. These include bleeding, swelling, and engorgement of veins.
Fluorescein angiography may be performed to confirm the diagnosis and to evaluate the extent of the affects of the blockage on the retina. Fluorescein angiography is a test in which a water-soluble dye is injected into a vein in the arm. The dye then quickly passes through the circulation to the eye, and serial photographs are taken to examine retinal circulation.
One possible complication associated with BRVO is swelling in the macula (the center of the retina, used for central vision), which creates a blockage in the vein known as macular edema. This blockage slows down the rate at which blood is able to leave the eye, which may cause some pooling of extra fluid in the center of the retina. This fluid may be reabsorbed naturally by the body or it may require treatment with laser, medication, or surgery.
The laser is a bright, highly focused beam of light that can seal some of the leaking vessels. A large, multicenter research study reported the benefit of laser treatment for patients with swelling in the macula.
A more rare and more threatening complication is the formation of abnormal new blood vessels (called neovascularization), which may grow on the iris (the colored part of the eye) or on the retinal surface. These abnormal vessels can bleed easily, causing further vision loss. Once detected, these abnormal blood vessels are treated with laser. After the blood clears, if the patient’s vision remains blurry due to persistent swelling, or if abnormal blood vessels are still detected, laser may again be helpful.
Kenalog (triamcinalone is the generic name) is a medication that has been used for many years to treat inflammation and swelling in the eye. This medication can be given as an injection next to the eye, known as a periocular injection, but is much more effective if injected directly into the eye, called an intravitreal injection.
During a retinal examination, the actual site of the BRVO can often be seen clearly on examination. If this is the case, and if simpler treatments are not effective, a microsurgical technique known as sheathectomy surgery can be used to open the sheath constricting the vein at the site of occlusion.
In most cases, visual acuity does eventually improve somewhat after a BRVO. The recovery phase involves the natural formation of collateral vessels by the body.
Imagine the area of blockage as a roadblock. These collateral vessels can be seen as a detour—a way for the blood to avoid the roadblock and return via an alternate route. Although many patients do experience a return of vision after a BRVO, often it is not a return to the level of vision they had before the occurrence of the occlusion. The amount of vision which returns depends upon the degree of blockage of the circulation and the amount of time required for collateral vessels to develop.