Retinal Artery Occlusion

Retinal artery occlusion is an eye emergency that occurs when blood flow to the retina is suddenly blocked, often leading to severe and painless vision loss in one eye within minutes or hours.

Table of contents

• What is Retinal Artery Occlusion?
• Types of Retinal Artery Occlusion
• What Causes This Condition?
• Warning Signs and Symptoms
• Who Is at Risk?
• How Is It Diagnosed?
• Treatment Options
• What to Expect
• Prevention
• Connection to Other Health Problems

What is Retinal Artery Occlusion?

Retinal artery occlusion happens when one of the blood vessels that carries oxygen-rich blood to your retina (the light-sensitive layer at the back of your eye) becomes blocked^[1]. Think of it like a pipe that gets clogged—when blood can’t flow through, the cells in your retina begin to suffer from lack of oxygen^[2].

Your retina is responsible for detecting light and turning it into signals that your brain interprets as vision. When blood flow is interrupted, the retinal cells can start to die within minutes to hours, depending on how complete the blockage is^[11]. This damage can result in permanent vision loss^[3].

This condition is considered the eye’s version of a stroke. Just as a stroke affects the brain when blood flow is blocked, retinal artery occlusion affects the eye^[1]. It requires immediate medical attention, as early treatment may help restore some vision in certain cases^[1].

Types of Retinal Artery Occlusion

There are two main types of retinal artery occlusion, classified by which blood vessel is affected^[4].

Central Retinal Artery Occlusion (CRAO)

Central retinal artery occlusion happens when the main artery supplying blood to the retina becomes blocked^[2]. This type often causes the most severe damage because it affects the entire retina. People with this condition typically experience sudden and complete vision loss in one eye^[15].

However, about 25% of people have an extra blood vessel called a cilioretinal artery in their eyes. If you have this extra artery and it’s not affected by the blockage, your central vision may be partly preserved^[2].

Central retinal artery occlusion makes up more than 90% of all retinal artery occlusion cases^[1].

Branch Retinal Artery Occlusion (BRAO)

Branch retinal artery occlusion occurs when a smaller branch of the retinal artery gets blocked^[4]. This type affects only a portion of the retina, so the vision loss is usually less severe than with central retinal artery occlusion. You might lose vision in a specific area of your visual field, such as your side vision, or you might not notice any symptoms at all if the affected area is small or not in the center of your eye^[2].

People with branch retinal artery occlusion have a better chance of keeping fair to good eyesight compared to those with the central type^[15].

What Causes This Condition?

Retinal artery occlusion is most commonly caused by a blockage in the blood vessel. This blockage can come from different sources^[2].

An embolus is the most frequent cause—this is a small piece of material that travels through your bloodstream and gets stuck in the retinal artery^[1]. The embolus is often a tiny blood clot or a piece of cholesterol that breaks off from somewhere else in your body, usually from the heart, the large blood vessel in your neck called the carotid artery, or the aorta (the main artery from your heart)^[2][5].

Less commonly, a blood clot can form directly inside the retinal artery at a spot where the artery wall has already been damaged by conditions like high blood pressure, diabetes, or atherosclerosis (a buildup of fatty deposits in the arteries)^[11].

In rare cases, retinal artery occlusion may be caused by giant cell arteritis, a serious condition involving inflammation of the artery walls^[1][2]. This type is called arteritic retinal artery occlusion and makes up less than 10% of cases^[1].

Other less common causes include trauma to the eye, increased pressure inside the eye, blood disorders such as sickle cell disease, disorders that make blood clot more easily, use of birth control pills, and damage from radiation treatments^[5][11].

Warning Signs and Symptoms

The hallmark symptom of retinal artery occlusion is sudden, painless loss of vision in one eye^[2][4]. This vision loss can happen very quickly, often within seconds to minutes.

Depending on which type you have and how severe the blockage is, you might experience:

• Complete blindness in one eye
• Severe blurring of vision in one eye^[15]
• Loss of a section of your visual field, such as your side vision^[2]
• Distorted vision^[4]
• Blind spots in your vision^[4]

Sometimes the blockage is only temporary. If the blockage breaks up quickly and blood flow is restored to the retina, the vision loss may last only a few seconds or minutes^[2]. This brief episode of vision loss is sometimes called amaurosis fugax and can be a warning sign that a more permanent blockage might occur^[5].

It’s important to understand that retinal artery occlusion almost always affects only one eye^[11]. Only 1% to 2% of cases involve both eyes^[2].

Who Is at Risk?

Retinal artery occlusion most commonly affects people in their 60s, and men are affected more often than women^[2][4]. About 1 in 100,000 people develop central retinal artery occlusion each year^[4].

The main risk factors include^[2][3]:

• High blood pressure
• Increasing age
• Carotid artery disease (narrowing or blockage of the large blood vessels in the neck)
• Atherosclerosis (fatty deposits in the arteries)
• Diabetes
• Abnormal heart rhythms such as atrial fibrillation
• Faulty heart valves (valvular heart disease)
• High cholesterol
• Smoking
• Obesity^[4]

Less common risk factors include tumors in the heart, intravenous drug abuse, disorders that contribute to blood clot formation (such as sickle cell disease), use of oral contraceptives, blood platelet abnormalities, and pregnancy^[2].

How Is It Diagnosed?

If you experience sudden vision loss, you should seek medical care immediately. An eye doctor will perform several tests to diagnose retinal artery occlusion^[3].

The first step is a dilated eye examination. Your doctor will put drops in your eye to widen your pupil so they can see the back of your eye more clearly^[3]. In central retinal artery occlusion, the doctor typically sees a characteristic “cherry red spot” in the center of the retina, where the middle appears red while the surrounding retina looks pale due to lack of blood flow^[2]. In branch retinal artery occlusion, the doctor sees an area of pale, whitish retina along the blocked blood vessel^[2].

Additional tests may include:

Fluorescein angiography involves injecting a special dye into a vein in your arm and then taking photographs of your retina. This test shows how blood flows through your retinal blood vessels and can reveal delays in blood flow caused by the blockage^[2][3].

Optical coherence tomography (OCT) provides detailed images of the central retina. It can show swelling in the inner layers of the retina in the affected area, which over time becomes much thinner than normal^[2][3].

Your doctor will also check your blood pressure and may order blood tests to measure cholesterol and triglyceride levels and to check for inflammation^[3]. Additional tests might be done to find the source of the blockage, including an electrocardiogram to check your heart rhythm, an echocardiogram to look for problems with your heart valves or blood clots in your heart, and ultrasound of the carotid arteries in your neck to check for narrowing or blockages^[3].

Treatment Options

Unfortunately, there is no proven treatment that reliably restores vision after retinal artery occlusion^[1][2]. Despite this, seeking immediate medical care is crucial because the blockage can be a warning sign of serious problems elsewhere in your body, particularly an increased risk of stroke^[4].

For any treatment to have a chance of working in central retinal artery occlusion, it must be given within a very short time window—probably within 4 to 6 hours after symptoms begin^[2][6]. After this time, the retinal cells have likely suffered irreversible damage from lack of oxygen.

Several therapies may be attempted, though none have been proven to consistently change the outcome^[2][6]:

• Ocular massage with a thumb to try to dislodge the clot^[2]
• Lowering the pressure inside the eye with medication to try to improve blood flow^[2]
• Paracentesis—removing a small amount of fluid from the front of the eye with a needle to suddenly lower eye pressure, which might help push the clot further down the blood vessel where it causes less damage^[2][8]
• Inhaling a mixture of oxygen and carbon dioxide (called carbogen) to try to dilate the retinal arteries^[2]

Some studies have looked at using clot-busting drugs (thrombolytics) delivered either through a vein or directly into the artery supplying the eye. While some case reports showed dramatic recovery of vision, recent controlled studies have not proven these treatments to be effective, and they can carry risks of serious bleeding^[6][8].

The most important aspect of treatment is managing the underlying conditions that caused the blockage and preventing future vascular events. This includes identifying and treating high blood pressure, high cholesterol, diabetes, and carotid artery disease^[1]. Your doctor may prescribe blood thinners such as aspirin or other anti-clotting drugs to reduce the risk of further blockages^[3].

What to Expect

The outlook for vision recovery after retinal artery occlusion is generally poor^[1][3]. Even with early treatment, most people do not regain their vision. Only about 21% to 35% of eyes affected by central retinal artery occlusion retain useful vision^[5].

The whitening of the retina that appears after the blockage generally lasts 4 to 6 weeks before fading^[2]. Over time, the affected areas of the retina become thinner than normal as the cells die^[2].

People with branch retinal artery occlusion tend to have a better prognosis than those with central retinal artery occlusion because less of the retina is affected^[15].

Possible complications include glaucoma (in cases of central retinal artery occlusion) and partial or complete loss of vision in the affected eye^[3].

Prevention

While you cannot always prevent retinal artery occlusion, you can take steps to reduce your risk by addressing the factors that contribute to blood vessel disease^[3]:

• Eating a low-fat diet
• Exercising regularly
• Stopping smoking
• Losing weight if you are overweight
• Managing high blood pressure
• Controlling diabetes
• Treating high cholesterol

These same measures help prevent other serious conditions like coronary artery disease and stroke^[3].

If you have already had a retinal artery occlusion in one eye, working with your doctor to manage these risk factors is especially important to reduce the chance of it happening in your other eye.

Connection to Other Health Problems

Retinal artery occlusion is strongly associated with an increased risk of other serious vascular events. The condition is similar to a cerebral stroke and shares the same risk factors^[1].

If you have retinal artery occlusion, you face a higher risk of having a stroke in your brain in the future^[1][3]. A blood clot in your eye may be a warning sign of clots elsewhere in your body^[3]. You also have an increased risk of ischemic heart disease^[1].

Because the embolus causing retinal artery occlusion often comes from the carotid artery in your neck, carotid artery disease is found in about 45% of cases, with significant narrowing (60% or more) occurring in 20% of cases^[5].

This is why your doctor will focus not only on trying to restore your vision but also on preventing further vascular events such as cerebral stroke and cardiovascular death^[1]. A complete evaluation to identify the source of the blockage and treat underlying conditions is essential.