Arteries carry blood from the heart to various parts of the body and veins return it. The venous circulation in the retina is like a tree with numerous branches, all of which drain into one major vein, the central retinal vein. When any one of these branches is blocked, the circulation of blood through the affected vein is halted or reduced, producing a back up of blood and fluid into the retinal tissue. An excessive accumulation of fluid is referred to as macular edema, which can cause blurry or distorted vision.
BRVO is more common in patients with high blood pressure, diabetes, atherosclerosis, or glaucoma. Smoking is also a significant risk factor. In some cases, no underlying cause is found. About one-quarter of patients with BRVO experience gradual spontaneous improvement in vision, but in others, the vision remains decreased or even worsens.
The only known way to improve vision is to treat the associated macular edema. Treatment options proven to be effective in reducing edema and improving vision to some degree include laser or intravitreal injection (injection of medicine into the eye). Medications that can be injected include vascular endothelial growth factor (VEGF) inhibitors such as Lucentis (FDA approved), Eylea (FDA approved) and Avastin (used off-label) or steroids such as Triamcinolone (used off-label) and Ozurdex (FDA approved). Laser is also sometimes used to treat the macular edema, but this is considered a second line treatment for most cases. Furthermore, if there is too much bleeding in the retina, laser cannot be performed.
Most patients notice some improvement in vision with treatment, although the degree of improvement often varies. Your retina specialist will review the risks, benefits, and alternatives of one or more of these treatment options with you in further detail and make tailored recommendations based on the unique findings of your eye.
Months later, some patients may develop an abnormal growth of fragile new blood vessels (neovascularization) on the surface of the retina or the iris. These blood vessels generally do not have any associated symptoms unless they should spontaneously rupture and bleed. If there is a significant amount of bleeding, vision can be quite dramatically reduced. Although the blood can resolve spontaneously, it can take weeks or months. Regular monitoring after initial diagnosis of BRVO is warranted since neovascularization can be caught and treated with laser to help lower the risk of sight-threatening bleeding. Vitrectomy surgery to remove blood is sometimes needed for persistent or recurrent bleeding. Finally, underlying medical conditions such as high blood pressure require treatment in order to lower the risk of another retinal vein occlusion.
