Retinal vein occlusion is a blockage of the small veins that carry blood away from the retina. The retina is the layer of tissue at the back of the inner eye that converts light images to nerve signals and sends them to the brain.

Central retinal vein occlusion; Branch retinal vein occlusion; CRVO; BRVO

Retinal vein occlusion is most often caused by hardening of the arteries (atherosclerosis) and the formation of a blood clot.

Blockage of smaller veins (branch veins or BRVO) in the retina often occurs when retinal arteries that have been thickened or hardened by atherosclerosis cross over and place pressure on a retinal vein.

Rick factors for retinal vein occlusion include:

• Atherosclerosis
• Diabetes
• High blood pressure (hypertension)
• Other eye conditions, such as glaucoma, macular edema, or vitreous hemorrhage

Because the risk of these disorders increases with age, retinal vein occlusion most often affects older people.

Blockage of retinal veins may cause other eye problems, including:

• Glaucoma (high pressure in the arteries), caused by new, abnormal blood vessels growing in the front part of the eye
• Macular edema, caused by the leakage of fluid in the retina

• Sudden blurring or vision loss in all or part of one eye

Tests to evaluate for vein occlusion include:

• Examination of the retina after dilating the pupil
• Fluorescein angiography
• Intraocular pressure
• Pupil reflex response
• Refraction
• Retinal photography
• Slit lamp examination
• Testing of side vision (visual field examination)
• Visual acuity

Other tests may include:

• Blood tests for diabetes, high cholesterol, and triglyceride levels
• Blood tests to look for a clotting or blood thickening (hyperviscosity) problem (in patients under age 40)

The health care provider should closely monitor any blockage for several months. Many harmful effects, such as glaucoma, take 3 or more months to develop after the occlusion.

Many people will regain vision, even without treatment. However, vision rarely returns to normal. There is no way to reverse or open the blockage.

You may need treatment to prevent another blockage from forming in the same or the other eye.

It's important to manage diabetes, high blood pressure, and high cholesterol levels. Some patients may receive aspirin or other blood thinners.

Treatment for the complications of retinal vein occlusion may include:

• Focal laser treatment, if macular edema is present
• Injections of anti-vascular endothelial growth factor (anti-VEGF) drugs into the eye. These drugs may block the growth of new blood vessels that can cause glaucoma. This treatment is still being studied.
• Laser treatment to prevent the growth of new, abnormal blood vessels that leads to glaucoma

The outcome varies. Patients with retinal vein occlusion often regain useful vision.

It is important to properly manage complications, such as macular edema and glaucoma. However, having either of these complications is more likely to lead to a poor outcome.

• Glaucoma
• Partial or complete vision loss in the affected eye

Call your health care provider if you have sudden blurring or vision loss.

Retinal vein occlusion is a sign of a general blood vessel (vascular) disease. The same measures used to prevent other blood vessel diseases, such as coronary artery disease, may decrease the risk of retinal vein occlusion.

These measures include:

• Eating a low-fat diet
• Getting regular exercise
• Maintaining an ideal weight
• Not smoking

Aspirin or other blood thinners may help prevent blockages in the other eye.

Controlling diabetes is important in general, and it may also be helpful for preventing retinal vein occlusion.

Sanborn GE, Magargal LE. Venous occlusive disease of the eye. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott, Williams & Wilkins: 2009:chap 15.

Wu L, Arevalo JF, Roca JA, Maia M, Berrocal MH, Rodriguez FJ, et al. Pan-American Collaborative Retina Study Group (PACORES). Comparison of two doses of intravitreal bevacizumab (Avastin) for treatment of macular edema secondary to branch retinal vein occlusion: results from the Pan-American Collaborative Retina Study Group at 6 months of follow-up. Retina. 2008;28:212-219.

Kreutzer TC, Alge CS, Wolf AH, Kook D, Burger J, Strauss R, et al. Intravitreal bevacizumab for the treatment of macular oedema secondary to branch retinal vein occlusion. Br J Ophthalmol. 2008;92:351-355.

Crouch ER, Crouch ER, Grant TR. Ophthalmology. In: Rakel RE, ed.Textbook of Family Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap41.