Amaurosis fugax

December 31, 2014

Synonyms

Overview

Amaurosis fugax involves loss of vision in one eye caused by a temporary lack of blood flow to the retina.

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.

If the blockage continues, vision loss may be followed by more serious nervous system symptoms. These symptoms can be similar to those of a stroke, including weakness or speech problems.

Causes

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 include

Heart disease, especially irregular heartbeat
Alcohol abuse
Cocaine use
Diabetes
Family history of stroke
High blood pressure
High cholesterol
Increasing age
Smoking (people who smoke one pack a day double their risk of a stroke)

Diagnosis

Despite the temporary nature of the vision loss, those experiencing amaurosis fugax are usually advised to consult a physician immediately as it is a symptom that usually heralds serious vascular events, including stroke. Restated, "because of the brief interval between the transient event and a stroke or blindness from temporal arteritis, the workup for transient monocular blindness should be undertaken without delay." If the patient has no history of giant cell arteritis, the probability of vision preservation is high; however, the chance of a stroke reaches that for a hemispheric TIA. Therefore, investigation of cardiac disease is justified.

A diagnostic evaluation should begin with the patient's history, followed by a physical exam, with particular importance being paid to the ophthalmic examination with regards to signs of ocular ischemia. When investigating amaurosis fugax, an ophthalmologic consult is absolutely warranted if available. Several concomitant laboratory tests should also be ordered to investigate some of the more common, systemic causes listed above, including a complete blood count, erythrocyte sedimentation rate, lipid panel, and blood glucose level. If a particular etiology is suspected based on the history and physical, additional relevant labs should be ordered.

If laboratory tests are abnormal, a systemic disease process is likely, and, if the ophthalmologic examination is abnormal, ocular disease is likely. However, in the event that both of these routes of investigation yield normal findings, or an inadequate explanation, noninvasive duplex ultrasound studies are recommended to identify carotid artery disease. Most episodes of amaurosis fugax are the result of stenosis of the ipsilateral carotid artery. With that being the case, researchers investigated how best to evaluate these episodes of vision loss, and concluded that for patients ranging from 36–74 years old, "...carotid artery duplex scanning should be performed...as this investigation is more likely to provide useful information than an extensive cardiac screening (ECG, Holter 24-hour monitoring and precordial echocardiography)." Additionally, concomitant head CT or MRI imaging is also recommended to investigate the presence of a "clinically silent cerebral embolism."

If the results of the ultrasound and intracranial imaging are normal, "renewed diagnostic efforts may be made," during which fluorescein angiography is an appropriate consideration. However, carotid angiography is not advisable in the presence of a normal ultrasound and CT.

Prognosis

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

Treatment

Treatment depends on the results of the evaluation. If there is evidence of blockage of more than 70% of the carotid artery, the patient may be considered for surgery to remove the blockage. The decision to do surgery will also be based on the presence and severity of other medical problems and the general health of the patient. If the patient is not a surgical candidate, treatment with aspirin or another blood thinning agent may be warranted. Lowering cholesterol, reducing high blood pressure and cessation of smoking can help decrease the risk of atherosclerosis.