Causes
Amaurosis fugax is primarily caused by a temporary blockage of blood flow to the retina, which is the light-sensitive tissue at the back of the eye. This blockage is usually due to a temporary clot or plaque fragment (embolus) that travels from an artery in the neck or heart to the retinal artery.- Atherosclerosis: The most common cause. Fatty plaque buildup (atherosclerosis) in the carotid arteries (major arteries in the neck that supply blood to the brain and eyes) can shed small pieces of plaque or blood clots, which then travel to the retinal artery.
- Carotid Artery Disease: Significant narrowing or blockages in the carotid arteries.
- Heart Conditions:
- Atrial Fibrillation (AFib): Irregular heartbeat can cause blood clots to form in the heart, which can then travel to the eye or brain.
- Heart Valve Disease: Damaged heart valves can also be a source of clots.
- Recent Heart Attack:
- Blood Clotting Disorders (Thrombophilia): Conditions that make blood more prone to clotting.
- Inflammatory Conditions:
- Giant Cell Arteritis (Temporal Arteritis): Inflammation of arteries, including those supplying the eye, which can cause severe and permanent vision loss if not treated promptly.
- Vasculitis: General inflammation of blood vessels.
- Migraine: Some types of migraine can cause transient vision changes, though typically affecting both eyes or presenting differently.
- Optic Nerve Problems: Rarely, temporary swelling or inflammation of the optic nerve.
- Severe Hypertension (High Blood Pressure): Uncontrolled high blood pressure can damage blood vessels, potentially leading to blockages.
Symptoms
The primary symptom is sudden, temporary vision loss in one eye. This vision loss is typically:- Monocular: Affects only one eye.
- Painless: Usually not accompanied by pain.
- Transient: Lasts for seconds to minutes, typically resolving completely within 15-20 minutes.
- Described as: A "curtain" or "shade" coming down over the vision, or dimming/blacking out, affecting part or all of the visual field in that eye.
Diagnosis
Because amaurosis fugax can be a warning sign of impending stroke, immediate medical evaluation is crucial to identify the underlying cause.- Medical History and Physical Exam: The doctor will ask about the details of the vision loss, any associated symptoms (e.g., weakness, numbness, speech difficulties), and risk factors for stroke or heart disease (e.g., high blood pressure, diabetes, smoking, family history).
- Eye Examination: An ophthalmologist will examine the retina to look for signs of previous or ongoing blockage (e.g., retinal emboli).
- Carotid Ultrasound (Duplex Ultrasound): This is a key non-invasive test to evaluate the carotid arteries in the neck for plaque buildup or narrowing.
- Echocardiogram: An ultrasound of the heart to check for blood clots or structural problems that could be a source of emboli.
- Electrocardiogram (ECG/EKG) and Holter Monitor: To check for atrial fibrillation or other heart rhythm abnormalities.
- Blood Tests: To check for cholesterol levels, blood sugar (diabetes), inflammatory markers (ESR, CRP for Giant Cell Arteritis), or clotting disorders.
- MRI or CT scan of the Brain: To check for evidence of past strokes or other brain abnormalities.
- Temporal Artery Biopsy: If Giant Cell Arteritis is suspected, a small sample of the temporal artery may be removed and examined.
Treatment
Treatment for amaurosis fugax is focused on preventing future, potentially more severe events like stroke or permanent vision loss by addressing the underlying cause.- Management of Risk Factors:
- Blood pressure control: Aggressively managing hypertension.
- Diabetes management: Strict control of blood sugar levels.
- Cholesterol management: Lowering high cholesterol, often with statin medications.
- Quit smoking: Essential for vascular health.
- Healthy diet and regular exercise.
- Medications:
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- Antiplatelet drugs: Aspirin is often prescribed to reduce the risk of blood clots. Clopidogrel (Plavix) may also be used.
- Anticoagulants (Blood Thinners): If the cause is a heart rhythm disorder like atrial fibrillation, anticoagulants (e.g., warfarin, DOACs like apixaban, rivaroxaban) are crucial to prevent clot formation.
- Corticosteroids: If Giant Cell Arteritis is diagnosed or strongly suspected, high-dose corticosteroids are started immediately to prevent irreversible vision loss in that eye or the other eye.
- Procedures and Surgery:
- Carotid Endarterectomy: A surgical procedure to remove plaque buildup from a narrowed carotid artery in the neck.
- Carotid Angioplasty and Stenting: A minimally invasive procedure where a balloon is used to open a narrowed carotid artery, and a stent is placed to keep it open.
- Management of Heart Conditions: Treating atrial fibrillation or heart valve disease.
What Happens After an Episode
An episode of amaurosis fugax is a transient ischemic attack of the eye, and it carries the same short-term stroke risk as a TIA affecting the brain. The vision returns, which tempts people to wait; the evaluation matters most in the first day or two, when the risk is highest.
It is worked up like a TIA, the same day
Vision that blacked out in one eye and returned is assessed within twenty-four hours, in an emergency department or rapid-access clinic, with carotid imaging, a heart rhythm check, and brain imaging. The transient ischemic attack page explains why the first week is the critical window, and the stroke page covers what the workup is trying to prevent.
Antiplatelet and statin treatment starts immediately
An antiplatelet medication such as aspirin, or clopidogrel when aspirin cannot be used, is started right away, and a high-intensity statin such as atorvastatin or rosuvastatin is prescribed regardless of the cholesterol number, because it stabilizes plaque as well as lowering lipids. When atrial fibrillation is found, an anticoagulant such as apixaban replaces the antiplatelet. Blood pressure targets tighten, and smoking cessation is treated as part of the prescription.
Carotid surgery has a deadline
A significantly narrowed carotid artery on the same side as the affected eye is treated with endarterectomy or stenting, and the benefit is greatest when it is done within two weeks of the episode. Our carotid disease and stroke prevention article explains how the degree of narrowing guides the decision, and the carotid artery disease page covers the procedures.
Over 50: rule out giant cell arteritis first
In anyone over 50, especially with a new headache, scalp tenderness, jaw pain on chewing, or aching shoulders, an inflammatory marker is drawn the same day to look for temporal arteritis. That condition can cause permanent blindness within days and is treated with high-dose prednisone the moment it is suspected, before the biopsy confirms it.
What it is confused with
Migraine aura produces shimmering zigzags that spread over minutes and affect both eyes, even when it feels one-sided; covering each eye in turn during an episode settles the question. Flashes and a shower of floaters point to the retina rather than a blood vessel, covered in our floaters and flashes article. A curtain that descends and does not lift is a retinal artery occlusion, an emergency in its own right. Our neurologic team coordinates the vascular workup with ophthalmology. NINDS and MedlinePlus publish patient guidance on transient ischemic attacks and amaurosis fugax.
If you have had even one episode of vision loss in one eye that resolved, contact us today rather than at your next scheduled visit.