Retinal artery occlusion is a sudden, painless blockage of a blood vessel that carries oxygen to the retina—the light-sensing tissue at the back of the eye. This blockage can lead to rapid and severe vision loss, often described as an “eye stroke,” and requires immediate medical attention even though no proven treatment exists to restore vision reliably.
Epidemiology
Retinal artery occlusion is an uncommon but serious eye condition that affects roughly one in every 100,000 people each year. The condition primarily strikes individuals in their 60s, with men being affected more commonly than women. Most people who develop this condition are older adults who have other health problems affecting their blood vessels.[1][4]
Central retinal artery occlusion, which affects the main blood vessel supplying the retina, accounts for the majority of cases and tends to result in more severe vision loss. Branch retinal artery occlusion, which involves smaller blood vessels, causes less extensive damage. Only about one to two percent of cases involve both eyes, meaning the condition almost always affects just one eye at a time.[2][7]
The condition is rare in younger individuals, though it can occur. When retinal artery occlusion strikes people under 40 years old, it’s more likely to be related to heart problems or blood clotting disorders rather than the typical causes seen in older adults.[5]
Causes
Retinal artery occlusion happens when something blocks the flow of blood through one of the arteries that supply the retina with oxygen and nutrients. The most common culprit is an embolus, which is a small piece of material that travels through the bloodstream and gets stuck in a blood vessel. This embolus is often made of cholesterol, though it can also be a blood clot, calcium, or even bacteria in rare cases.[1][2]
Most emboli that cause retinal artery occlusion originate from somewhere else in the body. The two most common sources are the carotid artery in the neck, which can develop fatty deposits called plaques, and the heart itself. When pieces of these plaques break off or when blood clots form in the heart, they can travel through the bloodstream until they reach the much smaller arteries in the eye, where they become lodged and block blood flow.[3][4]
Another cause of retinal artery occlusion is a thrombus, or blood clot that forms directly inside the retinal artery. This typically happens when the artery’s inner lining has already been damaged by chronic conditions like high blood pressure, diabetes, or atherosclerosis—a condition where cholesterol and other fatty substances build up on artery walls, narrowing them and reducing blood flow.[11]
In rare cases, retinal artery occlusion results from inflammation of the artery walls, a condition known as giant cell arteritis or temporal arteritis. This inflammatory condition is especially important to identify quickly because it can affect the other eye within hours if left untreated. However, giant cell arteritis accounts for only about two percent of retinal artery occlusion cases.[1][5]
Other less common causes include increased pressure inside the eye from conditions like glaucoma, direct trauma to the eye, carotid artery dissection (a tear in the artery wall), and certain blood disorders like sickle cell disease that make blood more likely to clot. In young women, the use of oral contraceptives has been linked to increased risk. Rarely, spasm of the central artery or complications from migraines can trigger an occlusion.[3][5]
Risk Factors
High blood pressure and advancing age are the two most significant risk factors for developing retinal artery occlusion. As people grow older, their blood vessels naturally undergo changes that make blockages more likely, while uncontrolled high blood pressure damages artery walls and promotes the formation of plaques and clots.[4][10]
Diabetes is another major risk factor because it affects blood vessels throughout the body, including those in the eyes. People with diabetes often have other conditions that compound their risk, such as high cholesterol and high blood pressure. Smoking significantly increases risk by damaging blood vessel linings and promoting atherosclerosis.[2][3]
Carotid artery disease, where the large blood vessels in the neck become narrowed or blocked, is found in nearly half of people who develop central retinal artery occlusion. About one in five people with this eye condition have severe narrowing—60 percent or more—of their carotid arteries. This connection explains why retinal artery occlusion is sometimes called an “eye stroke” and why it serves as a warning sign for potential brain strokes.[5]
Heart conditions also raise the risk considerably. Faulty heart valves, abnormal heart rhythms such as atrial fibrillation, and heart tumors can all lead to the formation of blood clots that travel to the eye. People who have had heart attacks or who have other forms of heart disease face elevated risk.[2][7]
Additional risk factors include obesity, high cholesterol levels, intravenous drug abuse, blood clotting disorders, sickle cell disease, and certain hereditary conditions like homocystinuria, which causes an excess buildup of a specific amino acid in the blood. Pregnancy and blood platelet abnormalities can also increase risk in some individuals.[2][7]
Symptoms
The hallmark symptom of retinal artery occlusion is sudden, painless loss of vision in one eye. This vision loss typically comes on abruptly, without any warning, and can range from partial to complete depending on which blood vessel is blocked and how extensive the blockage is. The absence of pain often leads people to delay seeking help, but this is precisely when immediate action matters most.[2][4]
When the central retinal artery—the main blood vessel supplying the retina—becomes blocked, people usually experience severe loss of vision throughout their entire visual field in the affected eye. This form of the condition, called central retinal artery occlusion, can result in vision dropping to only being able to detect hand movements or light, representing profound impairment.[2]
However, about one in four people who develop central retinal artery occlusion have an extra blood vessel called a cilioretinal artery that can partially compensate for the blocked main artery. When this extra artery is present and remains unaffected, it can preserve some central vision even when the main artery is blocked, greatly improving the person’s visual outcome.[2][7]
Branch retinal artery occlusion, which affects a smaller blood vessel, typically causes loss of a section of the visual field rather than complete blindness. People might lose their peripheral vision on one side, or develop a blind spot in part of their vision. If the blocked vessel supplies a small area that doesn’t include the central vision, the person might not even notice any symptoms at all.[2][4]
In some cases, people experience brief episodes of vision loss that last only seconds or minutes before vision returns. This temporary condition is called amaurosis fugax and represents a warning sign that shouldn’t be ignored. These fleeting episodes of blindness suggest that small emboli are temporarily blocking blood flow before breaking up or moving on, and they often precede a permanent occlusion.[5]
Other symptoms can include distorted vision, where straight lines appear wavy or objects look misshapen, and the appearance of blind spots or floaters. Some people describe their vision as cloudy or foggy. Loss of peripheral vision can occur, making it difficult to see objects to the side while central vision remains relatively intact.[4][10]
Prevention
Preventing retinal artery occlusion focuses on addressing the underlying cardiovascular risk factors that make blockages more likely. Since the same conditions that cause heart attacks and strokes also contribute to retinal artery occlusion, many prevention strategies overlap with general heart health recommendations.[3]
Managing blood pressure is crucial. People with high blood pressure should work with their healthcare provider to keep their blood pressure within a healthy range through lifestyle changes, medication, or both. Regular blood pressure monitoring helps ensure treatment is working effectively.[3]
Controlling diabetes through careful management of blood sugar levels, following a healthy diet, taking prescribed medications, and monitoring glucose regularly can reduce the risk of blood vessel damage that leads to occlusions. People with diabetes should have comprehensive eye examinations regularly to catch early signs of blood vessel problems.[2][7]
Following a low-fat diet helps reduce cholesterol and prevents the buildup of fatty deposits in arteries. Limiting saturated fats, trans fats, and dietary cholesterol while emphasizing fruits, vegetables, whole grains, and lean proteins supports vascular health. Some people may need cholesterol-lowering medications to achieve healthy levels.[3]
Stopping smoking is one of the most impactful steps anyone can take to reduce their risk. Smoking damages blood vessel walls, promotes inflammation, and accelerates atherosclerosis. Quitting at any age provides benefits, and healthcare providers can offer support through counseling, medications, or nicotine replacement therapy.[3]
Regular exercise supports cardiovascular health by improving circulation, helping control weight, and reducing blood pressure and cholesterol. Even moderate activity like brisk walking for 30 minutes most days of the week provides significant benefits. Weight loss for those who are overweight or obese reduces strain on the cardiovascular system.[3]
People at high risk may benefit from taking blood-thinning medications like aspirin or other anticoagulants. These medications help prevent blood clots from forming, though they must be prescribed by a doctor after weighing the benefits against the risk of bleeding. Aspirin or other anti-clotting drugs are particularly important for people with carotid artery disease.[3]
Regular medical checkups allow for early detection and treatment of risk factors. People should have their blood pressure, cholesterol, and blood sugar checked regularly, especially if they have a family history of cardiovascular disease. Those with known carotid artery disease may need periodic ultrasound examinations to monitor the degree of narrowing.[3]
Pathophysiology
Understanding what happens inside the eye during retinal artery occlusion helps explain why the condition causes such rapid and severe vision loss. The retina is a delicate layer of nerve tissue that lines the back of the eye and is responsible for converting light into electrical signals that the brain interprets as vision. Like all nerve tissue, the retina requires a constant supply of oxygen-rich blood to function properly.[2]
Blood reaches the retina primarily through the central retinal artery, which branches from the ophthalmic artery. Once inside the eye, the central retinal artery divides into smaller branch arteries that spread across the retina’s surface, ensuring that every region receives adequate blood supply. When any of these arteries becomes blocked, the affected portion of the retina suddenly loses its oxygen supply, a condition called ischemia.[1][6]
Retinal nerve cells are extremely sensitive to oxygen deprivation. Without oxygen, these cells begin to malfunction within minutes and start dying within hours. The extent of cell death depends on how complete the blockage is and how quickly blood flow can be restored. If the main central retinal artery is completely blocked, cells throughout the entire retina can suffocate and die, resulting in permanent and severe vision loss.[11]
When examined through an ophthalmoscope, a blocked retinal artery produces distinctive changes in the retina’s appearance. The affected retina becomes pale and whitish due to swelling of the nerve cells and lack of blood flow. At the center of the retina, in an area called the macula, a characteristic “cherry red spot” often appears. This spot occurs because the macula is thinner than surrounding retinal tissue, allowing the normal red color of underlying blood vessels to show through while the surrounding retina appears pale.[2][7]
The pale, whitish appearance of the retina typically lasts for four to six weeks before gradually fading. During this time, the inner layers of the retina undergo progressive damage. Over weeks to months, these damaged areas thin out considerably as dead cells are cleared away, a process called atrophy. This thinning can be seen clearly on specialized imaging tests called optical coherence tomography, which provides detailed cross-sectional views of retinal layers.[2][7]
The timing of treatment is critical because of how quickly retinal cells die without oxygen. Most experts believe that for any intervention to potentially save vision, it must happen within four to six hours after symptoms begin. This narrow time window exists because after about six hours of complete oxygen deprivation, retinal damage becomes irreversible. Even partial blockages that allow some blood flow can cause permanent damage if they persist long enough.[2][6]
When emboli are the cause of the blockage, they can sometimes be seen during eye examination as small, yellowish or white deposits lodged in retinal blood vessels. Cholesterol emboli appear shiny and yellowish, while calcium emboli look white. Seeing these emboli confirms the diagnosis and provides important information about where they originated, guiding further investigation of the heart, carotid arteries, or other potential sources.[5]
In cases caused by giant cell arteritis, the mechanism is somewhat different. Instead of an embolus blocking the vessel, inflammation of the artery walls leads to swelling and narrowing that restricts blood flow. This inflammatory process can rapidly affect multiple blood vessels, including those supplying the optic nerve and potentially both eyes, making urgent treatment with anti-inflammatory medications essential.[1]