Amaurosis fugax

Definition

Amaurosis fugax is loss of vision in one eye due to a temporary lack of blood flow to the retina.

Alternative Names

Transient monocular blindness

Causes, incidence, and risk factors

Amaurosis fugax is thought to occur when a piece of plaque in the carotid artery breaks off and travels to the retinal artery in the eye. Plaque is a hard substance that forms when fat, cholesterol and other substances build up in the walls of arteries. Pieces of plaque can travel through the bloodstream. Vision loss occurs as long as the blood supply to the artery is blocked.

Atherosclerosis of the arteries in the neck is the main risk factor for this condition. Risk factors for atherosclerosis include heart disease, high cholesterol, smoking, diabetes, and high blood pressure.

Symptoms

Symptoms include the sudden loss of vision in one eye. This usually only lasts seconds but may last several minutes. Some patients describe the loss of vision as a gray or black shade coming down over their eye.

Signs and tests

Tests include a complete eye and neurological exam. In some cases, an eye exam will reveal a bright spot where the clot is blocking the retinal artery. A carotid ultrasound or magnetic resonance angiography (MRA) scan should be done to evaluate a blockage in the carotid artery.

Routine blood tests such as cholesterol and blood sugar (glucose) should be done to check your risk for atherosclerosis, which increases with high cholesterol and diabetes.

Treatment

Treatment depends on the severity of the blockage. If more than 70% of the carotid artery appears blocked, your doctor may recommend surgery to remove the blockage. The decision to do surgery is also based on your overall health. See: Carotid artery surgery

Other treatments include:

• Balloon angioplasty
• Stenting

Both techniques are used to open up the area of the carotid artery that is blocked by plaque. These methods are promising, especially for patients who are not well enough to undergo major surgery.

If you are not a candidate for surgery, treatment with aspirin or other blood thinners may be necessary.

Expectations (prognosis)

Amaurosis fugax may be a sign of impending stroke. The attack itself usually does not result in permanent disability.

Complications

Although this condition does not result in any permanent damage, it is a sign of atherosclerotic disease and means you have an increased risk for stroke.

Calling your health care provider

Call your health care provider if any loss of vision occurs. If symptoms last for longer than a few minutes, or if there are any other symptoms accompanying the visual loss, it is important to seek immediate medical attention.

Prevention

To help prevent a stroke:

• Get screened for high blood pressure every 1 - 2 years, especially if you have a family history of high blood pressure.
• Have your cholesterol checked. If you are high risk, your LDL "bad" cholesterol should be lower than 100 mg/dL. Your doctor may recommend you try to reduce your LDL cholesterol to as low as 70 mg/dL.
• If you have high blood pressure, diabetes, high cholesterol, and heart disease, make sure you follow your doctor's treatment recommendations.
• Follow a low-fat diet.
• Quit smoking.
• Exercise regularly: 30 minutes a day if you are not overweight; 60 - 90 minutes a day if you are overweight.
• Do not drink more than 1 to 2 alcoholic drinks a day.

Aspirin therapy (81mg a day or 100mg every other day) is now recommended for stroke prevention in women under 65 as long as the benefits outweigh the risks. It should be considered for women over age 65 only if their blood pressure is controlled and the benefit is greater than the risk of gastrointestinal bleeding and brain hemorrhage. Ask your doctor if aspirin is right for you.

Your doctor may also recommend that you take aspirin or another blood thinner if you have had a TIA or stroke in the past, or if you currently have an irregular heart beat (such as atrial fibrillation), mechanical heart valve, congestive heart failure, or other risk factors for stroke.

References

Zivin JA. Hemorrhagic cerebrovascular disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 432.

Goldstein LB. Prevention and management of stroke. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Libby: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Saunders;2007:chap 58.