Definition of Retinal artery occlusion:

Retinal artery occlusion is a blockage in one of the small arteries that carry blood to the retina. The retina is a layer of tissue in the back of the eye that is able to sense light.

Causes, incidence, and risk factors:

Retinal arteries may become blocked by a blood clot or fat deposits that get stuck in the arteries. These blockages are more likely if there is hardening of the arteries (atherosclerosis) in the eye.

Clots may travel from other parts of the body and block an artery in the retina. The most common sources of clots are the carotid artery in the neck and the heart.

Most clots occur in people with conditions such as:

• Carotid artery disease, a condition in which the two large blood vessels in the neck become narrowed or blocked
• Diabetes
• Heart rhythm problem (atrial fibrillation)
• Heart valve problem
• High levels of fat in the blood (hyperlipidemia)
• High blood pressure
• Intravenous drug abuse
• Temporal arteritis (damage to arteries due to an immune response)

If a branch of the retinal artery is blocked, part of the retina will not receive enough blood and oxygen. If this happens, you may lose part of your vision.

Symptoms:

Sudden blurring or loss of vision may occur in:

• All of one eye (central retinal artery occlusion or CRAO)
• Part of one eye (branch retinal artery occlusion or BRAO)

The retinal artery occlusion may last for only a few seconds or minutes, or it may be permanent.

If the blood clot moves to another part of the brain, symptoms of a stroke may develop.

Signs and tests:

Tests to evaluate the retina may 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

General tests should include:

• Blood pressure
• Blood tests, including cholesterol and triglyceride levels and the erythrocyte sedimentation rate
• Physical examination

Tests to identify the source of a clot from another part of the body:

• Echocardiogram
• Electrocardiogram
• Heart monitor for abnormal heart rhythm
• Duplex Doppler ultrasound of the carotid arteries

Treatment:

There is no proven treatment for vision loss that involves the whole eye, unless it is caused by another illness that can be treated.

Several treatments may be tried. These treatments must be given within 2 - 4 hours after symptoms begin to be helpful. However, the benefit of these treatments has never been proven, and they are rarely used.

• Breathing in (inhaling) a carbon dioxide-oxygen mixture. This treatment causes the arteries of the retina to widen (dilate).
• Massage of the eye
• The clot-busting drug, tissue plasminogen activator (tPA)

The health care provider should look for the cause of the blockage. Blockages may be signs of a life-threatening medical problem.

Expectations (prognosis):

People with blockages of the retinal artery may not get their vision back.

Complications:

• Glaucoma (CRAO only)
• Partial or complete loss of vision in the affected eye
• Stroke (due to the same factors that contribute to retinal artery occlusion, not due to the occlusion itself)

Calling your health care provider:

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

Prevention:

Measures used to prevent other blood vessel (vascular) diseases, such as coronary artery disease, may decrease the risk of retinal artery occlusion. These include:

• Eating a low-fat diet
• Exercising
• Stopping smoking
• Losing weight if you are overweight

Sometimes blood thinners may be used to prevent the artery from becoming blocked again. Aspirin or other anti-clotting drugs are used if the problem is in the carotid arteries. Warfarin or other more potent blood thinners are used if the problem is in the heart.