Branch Retinal Artery Occlusion: Causes and Care
Understanding Branch Retinal Artery Occlusion
The central retinal artery is the main blood vessel that supplies oxygen and nutrients to the retina. It divides into smaller branches as it spreads across the retinal surface. A branch retinal artery occlusion occurs when one of these smaller branches becomes blocked, cutting off blood flow to the section of the retina it serves.
Without blood flow, the affected retinal tissue begins to suffer damage within minutes. The blockage usually happens at a point where an artery splits into two smaller branches, because these branching points tend to be narrower. In about 90 percent of cases, the blockage affects the temporal retinal vessels, which are the arteries on the side of the retina closer to your temple (Medscape, 2023).
A central retinal artery occlusion, or CRAO, blocks the main artery serving the entire retina. This causes more widespread and severe vision loss. BRAO blocks only one branch, so vision loss is typically limited to a portion of the visual field rather than all of it. Both BRAO and CRAO are forms of acute ischemic stroke affecting the eye and share many of the same underlying causes and risk factors.
Most cases of BRAO are caused by an embolus, which is a small piece of material that travels through the bloodstream and gets stuck in a blood vessel. The three most common types of emboli involved in BRAO are:
- Cholesterol emboli that break off from fatty plaques in the carotid arteries or aorta
- Platelet-fibrin emboli that form from blood clotting disorders or damaged blood vessels
- Calcific emboli that originate from diseased heart valves
In some cases, BRAO can also result from inflammation of the blood vessel walls (vasculitis) or from conditions that cause the blood to clot too easily (hypercoagulable states). Atherosclerosis, a buildup of fatty deposits in artery walls, is one of the most common underlying conditions that contributes to BRAO.
Who Is Affected and Risk Factors
BRAO is a relatively rare condition, with an incidence of around 5 per 100,000 persons per year (PMC, 2023). Most people who experience a retinal artery occlusion are in their 60s, and the condition is more common in men than in women. A large study using the American Academy of Ophthalmology's IRIS database found a prevalence of retinal vascular occlusion of 4.31 percent across all types, with BRAO accounting for 8.3 percent of those cases (Medscape, 2023).
Because BRAO is closely linked to blood vessel disease throughout the body, the risk factors are similar to those for heart attack and stroke. Common cardiovascular risk factors include high blood pressure, high cholesterol, diabetes, and a history of heart disease. Carotid artery disease is particularly important. Studies have found that about 30 percent of BRAO patients have 50 percent or greater narrowing of the carotid artery on the same side as the affected eye, and 66 percent have carotid plaques (AAO).
Smoking is a significant risk factor for BRAO. Research has shown that smoking rates among women with BRAO are significantly higher than in the general population (AAO). Smoking damages blood vessel walls, promotes atherosclerosis, and increases the tendency of blood to clot. Sedentary lifestyle, obesity, and poor diet also contribute to the vascular conditions that can lead to BRAO.
Heart valve disease and other cardiac conditions can be a direct source of emboli that travel to the retinal arteries. Studies have found that an abnormal echocardiogram showing an embolic source was present in about 42 percent of BRAO patients (AAO). Atrial fibrillation and other heart rhythm disorders also increase the risk because they can cause blood to pool and form clots in the heart.
Patients with BRAO have a higher risk of future cardiovascular and cerebrovascular events, including heart attack and stroke. A thorough medical workup can identify the underlying cause in as many as 90 percent of patients (AAO). This is why a retina specialist will often recommend a comprehensive evaluation of your heart and blood vessels after a BRAO diagnosis.
Signs and Symptoms
The most common symptom of BRAO is a sudden, painless loss of vision in one section of the visual field in one eye. For example, you might lose your ability to see to one side or notice a blank area in your field of vision. Because BRAO affects only one branch of the retinal artery, the vision loss is usually limited to the area of the retina that branch supplies rather than the entire eye.
If the blocked artery supplies a small or peripheral area of the retina, the vision loss may be subtle. Some people with BRAO do not notice any symptoms at all, and the condition is found during a routine eye exam. Others may notice mild blurring, a blind spot, or a sense that something is not right with their vision in one eye.
Any sudden change in vision in one eye should be treated as a medical emergency. See a retina specialist or go to the emergency room immediately if you experience sudden vision loss, a curtain or shadow over part of your vision, new blind spots, or sudden blurring in one eye. Time is critical because retinal tissue can be permanently damaged within hours of losing its blood supply.
Diagnosis and Testing
A retina specialist can often identify BRAO during a dilated eye exam. When the specialist looks at the retina, the affected area typically appears pale or whitish because it is not receiving blood flow. A visible embolus may be seen lodged at the branching point of an artery. The specialist may also notice swelling of the retina in the affected area.
To confirm the diagnosis and understand the extent of damage, a retina specialist may order imaging tests. Fluorescein angiography involves injecting a special dye into a vein in the arm and photographing it as it flows through the retinal blood vessels. This test shows exactly where the blockage is located and whether blood flow has been restored. Optical coherence tomography (OCT), a noninvasive scan of the retinal layers, can reveal swelling or thinning of the retina caused by the occlusion.
Because BRAO is a sign of vascular disease throughout the body, a retina specialist will typically recommend additional medical testing. A carotid ultrasound checks for narrowing or plaque buildup in the neck arteries. An echocardiogram (ultrasound of the heart) looks for heart valve disease, blood clots, or other cardiac sources of emboli. Blood tests may be ordered to check cholesterol levels, blood sugar, clotting factors, and markers of inflammation.
Depending on the results of the systemic workup, a retina specialist may refer you to a cardiologist, neurologist, or vascular surgeon. The goal is to identify and manage the underlying cause of the blockage to reduce the risk of future events, including stroke and heart attack.
Treatment Options
There is no proven treatment that reliably reverses the vision loss from BRAO. However, several approaches may be attempted if a patient is seen within the first two to four hours after symptoms begin. These include ocular massage to try to dislodge the embolus, breathing a carbon dioxide and oxygen mixture to dilate the retinal arteries, and removing a small amount of fluid from inside the eye to lower eye pressure and improve blood flow. No BRAO treatment has been shown to produce better visual outcomes than the natural course of the condition (AAO).
The most important part of BRAO treatment is identifying and managing the underlying vascular disease that caused the blockage. This may involve medications to lower blood pressure, cholesterol-lowering drugs such as statins, blood thinners or antiplatelet medications, and lifestyle changes. If significant carotid artery disease is found, a vascular procedure may be recommended to reduce the risk of stroke.
After a BRAO, a retina specialist will monitor the eye for possible complications. In some cases, new abnormal blood vessels can grow on the retina in response to reduced blood flow. This is called retinal neovascularization. If neovascularization occurs, laser treatment or intravitreal injections of anti-VEGF medication (drugs that block abnormal blood vessel growth) may be needed. Common anti-VEGF agents include Eylea (aflibercept), Lucentis (ranibizumab), and Avastin (bevacizumab), which is used off-label for eye conditions.
What to Expect
Many people with BRAO retain relatively good central vision. A study of 90 eyes examined within seven days of onset found that visual acuity was 20/40 or better in 74 percent of patients with permanent BRAO and 94 percent of patients with transient BRAO (AAO). However, the section of the visual field supplied by the blocked artery may remain permanently diminished. The degree of recovery depends on which artery was blocked, how long the blockage lasted, and whether blood flow was restored.
Some improvement in vision can occur in the weeks and months following a BRAO as swelling in the retina resolves and the eye adapts. Most of the visual recovery that will happen tends to occur within the first few weeks. After the acute phase, there are no proven treatments to reverse the vision loss that has already occurred. A retina specialist will schedule follow-up appointments to track your progress and watch for complications.
Because BRAO indicates a higher risk for cardiovascular and cerebrovascular events, long-term health monitoring is essential. Regular visits with a primary care physician or cardiologist to manage blood pressure, cholesterol, and blood sugar can significantly reduce the chance of a more serious event such as a heart attack or stroke. Your retina specialist will also continue to monitor the health of both eyes over time.
Living with Branch Retinal Artery Occlusion
If BRAO has caused a permanent blind spot or loss of part of the visual field, adapting to this change takes time. Many people learn to compensate by turning their head slightly to use the unaffected parts of their vision. A low-vision specialist can provide strategies and tools to help with daily activities. Driving may be affected depending on the size and location of the visual field loss, and a formal visual field test may be required to determine driving eligibility.
Taking steps to improve cardiovascular health is one of the most important things you can do after a BRAO. Key steps include quitting smoking, eating a heart-healthy diet rich in fruits, vegetables, and whole grains, exercising regularly, managing blood pressure and cholesterol, and taking medications as prescribed by your physician. These lifestyle changes protect not only your eyes but also your heart and brain.
Sudden vision loss can be distressing and may cause anxiety about future events. It is normal to feel worried or frustrated. Talking with your retina specialist about your concerns can help you understand your prognosis and feel more in control. Support groups for people with vision loss can also provide helpful coping strategies and a sense of community.
When to See a Retina Specialist
See a retina specialist or go to the emergency room immediately if you experience sudden loss of vision in one eye, a shadow or curtain covering part of your visual field, or new blind spots that appear without warning. These symptoms may indicate a retinal artery occlusion or another serious eye condition. Prompt evaluation is critical because early intervention may help preserve vision and because these symptoms can signal an increased risk of stroke.
If you have been diagnosed with BRAO, regular follow-up appointments with a retina specialist are important. These visits allow the specialist to check for complications such as neovascularization, monitor the health of the retina, and coordinate care with your other physicians. Even if your vision feels stable, keeping these appointments helps protect your long-term eye health and overall well-being.
Questions and Answers
In most cases, the area of vision affected by BRAO does not fully return to normal. Some patients experience partial improvement as retinal swelling resolves, particularly in the first few weeks. However, after the acute phase, there are no proven treatments that can reverse the damage caused by the loss of blood flow. The good news is that many patients retain good central vision, which is important for reading and recognizing faces.
Yes. BRAO is considered a form of acute ischemic stroke affecting the eye, and it shares many of the same underlying causes as strokes affecting the brain. Patients with BRAO have a higher risk for cardiovascular and cerebrovascular events. This is why a retina specialist will recommend a thorough evaluation of your carotid arteries, heart, and blood vessels after a diagnosis of BRAO. Managing the risk factors identified during this workup can help reduce your chances of a future stroke or heart attack.
Retinal artery occlusions and retinal vein occlusions are both types of retinal vascular disease, but they involve different blood vessels. BRAO involves a blockage in an artery that carries blood to the retina, while a retinal vein occlusion involves a blockage in a vein that carries blood away from the retina. Artery occlusions tend to cause more sudden and defined areas of vision loss, while vein occlusions often cause more gradual symptoms with swelling and bleeding in the retina. The underlying risk factors overlap, but treatment approaches differ.
Most patients with BRAO do not need eye injections. However, if the blocked blood flow triggers the growth of abnormal new blood vessels on the retina, a retina specialist may recommend intravitreal injections of anti-VEGF medication to control this complication. Laser treatment may also be used in some cases. Your retina specialist will monitor your eye at follow-up visits and recommend treatment only if complications develop.
The most impactful changes focus on cardiovascular health. Quitting smoking is especially important because smoking significantly increases the risk of vascular disease. Eating a balanced diet low in saturated fat and high in fruits, vegetables, and whole grains supports healthy blood vessels. Regular physical activity, maintaining a healthy weight, and carefully managing conditions like high blood pressure, diabetes, and high cholesterol all help reduce the risk of future vascular events in the eyes, heart, and brain.