Branch Retinal Vein Occlusion (BRVO) is similar to a central retinal vein occlusion, but only effects a portion of the retina. A BRVO occurs when a branch of the retinal vein becomes blocked. The blockage usually occurs where a retinal artery crosses over and compresses a retinal vein. The segment of the retina drained by the blocked vein becomes swollen with blood. Where the vessel is blocked, leakage often occurs, causing retinal swelling. When swelling occurs in the central retina it is called macular edema, and may result in loss of vision. As in CRVO, vision loss can also occur if abnormal blood vessels grow in the front or back of the eye.
Patients with a BRVO often have blurred vision from retinal hemorrhage or macular edema. Occasionally spots, strands, or a curtain may occur due to vitreous hemorrhage. Eye pain may be caused by neovascular glaucoma.
In addition to a dilated eye exam, a test called Fluorescein Angiography may be required. During this test a dye is injected into a vein in the arm. Special photographs are taken of the retina as the dye passes through the eye. Blocked or abnormal blood vessels will become detectable to the physician. Optical Coherence Tomography (OCT), a scanning laser which images a slice or cross section of the retina, may be performed to determine if macular edema is present. These tests aid the diagnosis and may help determine the need for treatment.
If vision loss is due to macular edema, treatment is often indicated. There are two treatments available; laser and intravitreal therapy. Sometimes they are used together.
Laser Treatment will decrease the leakage which is causing macular edema. Studies have shown that patients who receive laser for macular edema are twice as likely to regain good vision. If abnormal blood vessels are growing in the eye, more extensive laser treatment may be necessary. Laser may be applied in several sessions.
Intravitreal Drug Therapy involves placing medication into the vitreous, or main cavity of the eye. The injected medication acts upon the damaged blood vessels to reduce leakage and resolve macular edema. This treatment is the most effective way to cause resolution of macular edema and improve vision. Intravitreal drug therapy may involve ongoing treatments; sometimes over many years.