Imagine you are going about your day when, without any pain or warning, a gray or black curtain seems to descend over the vision in one of your eyes. For a few seconds or minutes, your sight is partially or completely obscured, only for it to return just as suddenly as it left, leaving you shaken and confused. This startling event is known as amaurosis fugax. While it is easy to dismiss such a brief episode, it is crucial to understand that this is not a minor eye problem. Amaurosis fugax is a transient ischemic attack (TIA) of the eye, a powerful and direct warning sign of a dangerously reduced blood flow that could lead to a permanent stroke. Recognizing this symptom for what it is, a true medical emergency, and seeking immediate medical attention is the single most important step you can take to prevent a life-altering or fatal event.

The term amaurosis fugax is Latin for “fleeting darkness” or “transient blindness.” It is not a disease in itself, but rather a critical symptom that signals a temporary lack of blood flow (ischemia) to the retina. The retina is the light-sensing tissue that lines the back of the eye; it acts like the film in a camera or the sensor in a digital camera, capturing images and sending them to the brain via the optic nerve.

To understand why this is so serious, it is helpful to think of the retina as a high-definition movie screen that requires a constant and robust power supply to function. The central retinal artery is the main power cable that brings oxygen-rich blood to this screen.

• In amaurosis fugax, a temporary blockage, usually a tiny blood clot or a small piece of cholesterol plaque, travels through the bloodstream and gets stuck in this power cable, cutting off the blood supply.
• Deprived of oxygen, the movie screen instantly goes dark.
• After a few seconds or minutes, the small blockage often breaks up or moves on, the power is restored, and the screen flickers back on.

While the vision returns to normal, the event is an unmistakable sign that there is a problem “upstream” in the main power lines, most often in the large carotid arteries in the neck. It is a powerful warning that these arteries are diseased and could send a much larger blockage to the brain at any time, causing a permanent power outage, a major stroke. Because the retina is an extension of the brain, a temporary loss of blood flow to the eye is just as serious as a temporary loss of blood flow to the brain (a TIA).

I’ve often seen patients dismiss a “blackout” in one eye, thinking it’s just eye strain. But this is often your body sending an early signal about vascular trouble, it’s crucial to investigate quickly.

Amaurosis fugax is caused by temporary occlusion (blockage) of the central retinal artery or one of its smaller branches. This blockage temporarily starves the retina of the oxygen it needs to function. The source of this blockage can come from several different places.

Embolic Causes (The Most Common)

An embolus is a small piece of material that breaks off from one part of the body, travels through the bloodstream, and gets lodged in a smaller vessel.

• Atherosclerosis of the Carotid Artery: This is the single most common cause of amaurosis fugax. The carotid arteries are the two large blood vessels in your neck that supply blood to your brain and eyes. Over time, due to factors like high cholesterol and high blood pressure, fatty deposits called plaque can build up on the inner walls of these arteries (a process called atherosclerosis). A small piece of this plaque can break off and travel directly to the retinal artery, causing a temporary blockage.
• Cardioembolic Causes: A small blood clot can form within the chambers of the heart, break loose, and travel to the eye. This is most often associated with an irregular heart rhythm called atrial fibrillation (AFib) or heart valve problems.

Hemodynamic Causes

In some cases, the vision loss is not caused by a traveling clot, but by a temporary drop in blood flow through a severely narrowed artery. This can happen in patients with critical carotid artery stenosis (narrowing) if their blood pressure drops suddenly.

Inflammatory Causes (Vasculitis)

Rarely, amaurosis fugax can be caused by inflammation of the blood vessels, a condition called vasculitis. Giant Cell Arteritis (GCA) is an inflammatory disease of the large and medium arteries, particularly those in the head and neck, that typically affects older adults. The inflammation can cause a blockage of the arteries supplying the eye, leading to amaurosis fugax.

In older patients, I’m most concerned about carotid artery disease. But in younger individuals, I also consider cardiac causes or inflammatory conditions like GCA, especially when symptoms are recurrent.

A person develops amaurosis fugax because they have an underlying medical condition that puts them at risk for vascular blockages.

The major risk factors include:

• High blood pressure (hypertension)
• High cholesterol (hyperlipidemia)
• Diabetes mellitus
• Cigarette smoking
• Older age (risk increases significantly after age 55)
• A personal or family history of stroke, TIA, or heart disease
• Atrial fibrillation or other known heart conditions
• A sedentary lifestyle and obesity

Patients are often surprised when I tell them their eye problem is actually a circulation problem. I explain it’s like a warning light, not just about their eyes, but their brain and heart, too.

The hallmark symptom of amaurosis fugax is distinctive, and recognizing it is crucial.

The classic presentation includes the following features:

• Painless, transient loss of vision in one eye (monocular). It is not associated with any eye pain, redness, or headache.
• It is often described as a “curtain” or “shade” descending or ascending to cover the field of vision. Some describe it as temporary dimming or fogging.
• The duration is typically very brief, lasting anywhere from a few seconds to a few minutes.
• Vision then returns completely to normal, with no lasting effects on sight from the episode itself.

In some cases, the episode of vision loss may be accompanied by other TIA symptoms, such as weakness or numbness on one side of the body or difficulty speaking. Any of these symptoms, alone or in combination, constitute a medical emergency.

Clinically, the curtain-like shadow descending over one eye is a red flag. If I hear that, I immediately think about embolic causes and begin evaluating stroke risk.

Diagnosing Amaurosis Fugax involves ruling out serious systemic causes. A comprehensive eye exam is followed by tests focused on vascular health and clot risk. The diagnostic process focuses on evaluating the three main potential sources of a blockage: the arteries in the neck, the brain, and the heart.

1. Carotid Artery Imaging: This is a critical first step.
   • A carotid Doppler ultrasound is a non-invasive test that uses sound waves to create images of the carotid arteries and measure the blood flow through them. It can accurately detect plaque buildup and the degree of narrowing (stenosis).
   • A CT angiogram (CTA) or MR angiogram (MRA) may also be used to get more detailed images of the arteries in the neck and head.
2. Brain Imaging:
   • A CT scan or MRI of the brain is performed to see if the patient has also suffered a small, silent stroke at the same time as their episode of vision loss.
3. Cardiac Evaluation:
   • An ECG and an echocardiogram are performed to look for heart rhythm problems like atrial fibrillation or sources of clots in the heart.
4. Ophthalmologic Examination: A thorough eye exam by an ophthalmologist is important to rule out other eye conditions. In some cases, the ophthalmologist may be able to see the tiny cholesterol plaque (called a Hollenhorst plaque) still lodged in one of the small retinal arteries.
5. Blood Tests: To check for high cholesterol, diabetes, and inflammatory markers (for vasculitis).

I never stop at the eye exam. When a patient reports Amaurosis Fugax, I refer for urgent vascular imaging, because detecting a carotid plaque early can prevent a devastating stroke later.

Treatment focuses on preventing further vascular events, especially stroke. Managing the underlying cause is the key to preventing recurrence.

1. Medical Management

This is the foundation of treatment for almost all patients.

• Antiplatelet Therapy: Patients are immediately started on a daily antiplatelet medication, such as aspirin or clopidogrel. These drugs make the blood platelets less “sticky” and reduce the risk of forming a blood clot.
• Statin Therapy: A high-dose statin medication is prescribed to aggressively lower LDL (“bad”) cholesterol. Statins also help stabilize plaque in arteries, making it less likely to rupture.
• Aggressive Risk Factor Control: This involves using medications to tightly control high blood pressure and diabetes, and counseling on smoking cessation.

2. Surgical or Interventional Treatment

For patients who are found to have a severe narrowing (typically 70% or more) of their carotid artery, a procedure to remove the blockage may be recommended to significantly reduce the risk of a future stroke (NINDS, 2023).

• Carotid Endarterectomy: This is a surgical procedure where a vascular surgeon opens the carotid artery and physically scrapes out the plaque to restore normal blood flow.
• Carotid Artery Stenting: This is a less invasive procedure where an interventionist threads a catheter to the site of the blockage and deploys a stent (a small mesh tube) to expand the narrowed artery and hold it open.

3. Treatment for Other Causes

If the cause is found to be atrial fibrillation, the patient will be started on a blood thinner (anticoagulant). If Giant Cell Arteritis is diagnosed, the treatment is high-dose corticosteroids.

When I start someone on aspirin or statins after a vision blackout, I tell them we’re not just treating their eye, we’re protecting their brain. That one episode may have prevented a much bigger problem.

Amaurosis fugax, or a “fleeting darkness” over one eye, may seem like a minor and temporary inconvenience, but it must be recognized as one of the most serious warning signs the body can produce. It is a true transient ischemic attack of the eye, signaling that the same vascular disease process that causes strokes is active. The return of normal vision should not be a cause for reassurance, but rather a call to urgent action. Anyone who experiences a sudden, painless, curtain-like loss of vision in one eye, no matter how brief, must seek immediate emergency medical evaluation. What I always tell my patients is this: vision loss that comes and goes isn’t harmless, it’s your body asking for help. If we listen and act early, we can prevent something far worse from happening.

1. American Academy of Ophthalmology (AAO). (2023). What is amaurosis fugax? Retrieved from https://www.aao.org/eye-health/diseases/what-is-amaurosis-fugax
2. Mayo Clinic. (2023). Amaurosis fugax. Retrieved from https://www.mayoclinic.org/diseases-conditions/amaurosis-fugax/symptoms-causes/syc-20369826
3. National Institute of Neurological Disorders and Stroke (NINDS). (2023). Stroke. Retrieved from https://www.ninds.nih.gov/health-information/disorders/stroke
4. Mayo Clinic. (2023). Amaurosis fugax. Retrieved from https://www.mayoclinic.org/