Retinal artery occlusion is a blockage of the blood supply in the arteries to the retina -- the light-sensitive tissue in the back of the eye.

Retinal arteries may become blocked by a blood clot or substances (such as fat or plaque) that get stuck in the arteries. These blockages may occur due to hardening of the arteries in the eye.

Also, clots may travel from other parts of the body and block an artery in the retina. A common source of a clot would be from the carotid artery in the neck or from the heart lining.

Most clots are caused by conditions such as:

• Diabetes
• Disease of the two large blood vessels in the neck (carotid artery disease)
• Disorder of high blood fats (hyperlipidemia)
• Heart rhythm problem (atrial fibrillation)
• High blood pressure

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

Retinal artery blockage or occlusions may last from only a few seconds to a few minutes. They also may cause permanent vision loss. The amount of vision loss is partly related to the location of the blockage.

People with retinal arterial occlusion, whether it is temporary or permanent, have a risk of stroke because clots may also move to the brain.

Retinal vessel occlusion more often affects older people. Risk factors are related to the disorders that cause the blockage.

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

Tests to evaluate the retina may include:

• Color vision
• Examination of the retina after the pupil is dilated
• Fluorescein angiography
• Intraocular pressure
• Pupil reflex response
• Refraction test
• Retinal photography
• Slit lamp examination
• Testing of side vision (visual field examination)
• Test that measures the electrical activity of the retina (electroretinogram)
• Visual acuity

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

• Echocardiogram
• Heart monitor for abnormal heart rhythm
• Ultrasound or Doppler ultrasound of the carotid arteries

Other tests may include:

• Blood pressure
• Cholesterol and triglyceride levels
• Complete physical exam

Breathing in (inhaling) a carbon dioxide-oxygen mixture has been used to treat blockages in the arteries. This treatment causes the arteries of the retina to widen (dilate). It may allow the clot to move down the artery and sometimes break up, which reduces the area of the retina that is affected.

The health care provider should look for the cause of the blockage. Blockages may be signs of a life-threatening medical problem. Patients with retinal artery occlusions should be screened for:

• Cranial arteritis
• Carotid artery blockage
• Heart rhythm disturbances
• Heart valve disease
• High blood pressure

The use of the clot-busting drug, tissue plasminogen activator (tPA), within a few hours of retinal artery occlusion may be helpful.

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

• Partial or complete loss of vision in the affected eye
• Similar problem occurring again in the same or the other eye
• Stroke

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

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

Aspirin is commonly used to prevent the artery from becoming blocked again. It is also helpful to control atrial fibrillation.

Vortmann M, Schneider JI. Acute monocular visual loss. Emerg Med Clin North Am. 2008;26:73-96.

Pokhrel PK, Loftus SA. Ocular emergencies. Am Fam Physician. 2007;76:829-836.