Retinal Vascular Occlusions: Protecting Your Vision
Understanding Retinal Vascular Occlusions
A retinal vascular occlusion is a blockage in one of the blood vessels that supply the retina. The retina depends on a steady flow of blood to function properly. When a vein or artery in the retina is blocked, the nerve cells in that area may not get the oxygen they need. This can cause sudden vision changes and may lead to lasting damage if not treated promptly.
Retinal vein occlusion (RVO) occurs when a vein that carries blood away from the retina becomes blocked. There are two main types. Branch retinal vein occlusion (BRVO) affects a smaller vein in the retina and is the more common form. Central retinal vein occlusion (CRVO) affects the main vein that drains blood from the entire retina and tends to cause more widespread damage.
Most BRVOs happen at a spot where a retinal artery and vein cross over each other. At these crossings, the artery can press on the vein, narrowing it. This narrowing creates turbulent blood flow that promotes clotting. When a clot forms, it blocks blood from draining properly. The backup of blood can cause swelling in the macula (the center of the retina responsible for sharp vision) and may starve parts of the retina of oxygen, a condition called ischemia.
Retinal artery occlusion (RAO) occurs when the artery that carries oxygen-rich blood to the retina is blocked. Central retinal artery occlusion (CRAO) affects the main artery and often causes severe, sudden vision loss. Branch retinal artery occlusion (BRAO) affects a smaller branch of the artery and may cause a more limited area of vision loss.
The blockage is often caused by an embolus, which is a small piece of material, such as cholesterol, that travels through the bloodstream and lodges in the artery. It can also be caused by a thrombus, which is a blood clot that forms at the site of the blockage. A retinal artery occlusion is considered a medical emergency because the retina can be permanently damaged within minutes to hours without blood flow.
In retinal vein occlusions, the blocked vein causes blood and fluid to leak into the retina. The body also produces higher levels of vascular endothelial growth factor (VEGF), a protein that triggers the growth of abnormal new blood vessels. These new vessels are fragile and prone to bleeding. If they bleed into the vitreous (the gel that fills the eye), it causes a vitreous hemorrhage that can severely cloud vision. Abnormal vessel growth on the iris can also lead to a painful type of glaucoma (high eye pressure).
In retinal artery occlusions, the retina is deprived of oxygen. Without a quick restoration of blood flow, the affected nerve cells can die. This makes artery occlusions particularly urgent. CRAO is sometimes compared to a stroke of the eye because the mechanism is similar to what happens in the brain during a stroke.
Who Is Affected and Risk Factors
Retinal vein occlusion is one of the most common retinal vascular disorders. The global prevalence of any RVO is approximately 0.77% in people aged 30 to 89 years, which translates to roughly 28 million people worldwide (PMC, 2019). BRVO is more common than CRVO, with global prevalence rates of 0.64% and 0.13%, respectively (PMC, 2019). In the United States, the age- and sex-standardized prevalence is about 5.20 per 1,000 people for any RVO (Archives of Ophthalmology, 2010).
Retinal artery occlusions are less common but can be devastating. Central retinal artery occlusion has an age- and sex-adjusted incidence of 1.9 per 100,000 person-years in the United States (Stroke: Vascular and Interventional Neurology, 2023).
The risk factors for retinal vascular occlusions overlap closely with those for heart disease and stroke. High blood pressure (hypertension) is the strongest risk factor, with studies showing it more than doubles the risk of RVO, with a meta-odds ratio of 2.82 (PMC, 2019). For BRVO specifically, hypertension carries an even higher odds ratio of 5.42 (Archives of Ophthalmology, 2010).
Other cardiovascular risk factors include:
- Diabetes mellitus, which increases the odds of BRVO by about 2.43 times (Archives of Ophthalmology, 2010)
- High cholesterol and high triglycerides (hyperlipidemia)
- Heart disease and atherosclerosis (hardening of the arteries)
- Smoking, which damages blood vessel walls
The risk of retinal vascular occlusions increases with age. Each decade of life brings a higher likelihood of developing these conditions. Most patients with retinal artery occlusions are in their 60s, and men are affected more often than women (Stroke: Vascular and Interventional Neurology, 2023). Lower education level has also been associated with increased odds of RVO, possibly because of its link to reduced access to preventive health care (Archives of Ophthalmology, 2010).
Eye-specific factors can also play a role. In BRVO, changes in the blood vessels visible during an eye exam, such as arteriovenous nicking (where an artery compresses a vein at a crossing point) and focal arteriolar narrowing, are associated with a higher risk.
Signs and Symptoms
The hallmark symptom of both BRVO and CRVO is a sudden, painless change in vision. Many patients notice blurry or distorted vision because of macular edema (swelling in the center of the retina). In BRVO, the vision loss may affect only a portion of the visual field, corresponding to the area served by the blocked vein. In CRVO, the vision loss is often more widespread.
Some patients with CRVO develop secondary complications such as neovascular glaucoma, which can cause pain, redness, and irritation. In rare cases where a vein occlusion goes undetected, visual floaters from a vitreous hemorrhage may be the first noticeable symptom.
Retinal artery occlusion typically causes sudden, painless loss of vision in one eye. The vision loss with CRAO is usually severe and happens within seconds to minutes. With BRAO, the vision loss may be partial, affecting only the area of the visual field supplied by the blocked branch.
Because a retinal artery occlusion can signal a higher risk of stroke, it requires immediate medical attention. If you experience sudden vision loss in one eye, see a retina specialist or go to the emergency room immediately. Time is critical for both protecting vision and evaluating stroke risk.
Not every retinal vascular occlusion presents with dramatic vision loss. Some people notice a gradual decline in vision quality over days or weeks, particularly with milder forms of BRVO. Others may not realize they have a problem until a routine eye exam reveals signs of a past occlusion. Regular eye exams are important for detecting these conditions, especially if you have cardiovascular risk factors.
Diagnosis and Testing
A retina specialist will begin with a thorough eye examination, including a dilated fundus exam. During this exam, special eye drops widen the pupil so the specialist can view the retina in detail. In retinal vein occlusions, the specialist may see swollen, twisted veins, areas of bleeding, and cotton-wool spots (small white patches indicating nerve fiber damage). In retinal artery occlusions, the retina may appear pale or whitened in the affected area.
Optical coherence tomography (OCT) is a non-invasive imaging test that creates detailed cross-sectional images of the retina. It is especially useful for measuring macular edema and tracking how well treatment is working. OCT scans can detect even small amounts of fluid in the retina that might not be visible during a standard exam.
Fluorescein angiography is another important test. A special dye is injected into a vein in the arm. As the dye travels through the blood vessels in the eye, photographs are taken to reveal areas of blockage, leakage, or abnormal blood vessel growth. This test helps the retina specialist determine how severe the occlusion is and whether ischemia is present.
Because retinal vascular occlusions are closely linked to cardiovascular disease, a retina specialist will often recommend a full medical workup. This may include blood pressure checks, blood sugar testing, cholesterol panels, and heart rhythm monitoring. For retinal artery occlusions in particular, imaging of the carotid arteries (the major blood vessels in the neck) may be recommended to check for plaque that could send emboli to the eye or brain. This systemic evaluation is a critical step because treating the underlying health conditions helps reduce the risk of future vascular events in the eye and elsewhere in the body.
Treatment Options
Anti-VEGF injections (medications that block vascular endothelial growth factor) are the primary treatment for macular edema caused by retinal vein occlusions. These medications are injected directly into the vitreous cavity of the eye in a procedure called an intravitreal injection. By blocking VEGF, they reduce swelling, slow abnormal blood vessel growth, and help preserve or improve vision.
Several anti-VEGF medications are FDA-approved for treating RVO:
- Lucentis (ranibizumab), approved in 2010, was the first anti-VEGF drug approved for RVO and is typically given every four weeks.
- Eylea (aflibercept) was approved for CRVO in 2012 and for BRVO in 2014, with dosing typically every four to eight weeks after an initial loading phase.
- Vabysmo (faricimab), a bispecific antibody that targets both VEGF-A and angiopoietin-2, was approved for RVO in October 2023. It may allow dosing intervals of up to every 16 weeks for some patients.
- Eylea HD (high-dose aflibercept) was approved for RVO in November 2025, based on results from the QUASAR trial. It may allow dosing up to every eight weeks.
- Avastin (bevacizumab) is FDA-approved for cancer treatment but is widely used off-label for retinal vein occlusion. It is typically given every four to six weeks.
For patients who do not respond well to anti-VEGF therapy, or for chronic and stubborn cases of macular edema from RVO, steroid implants may be considered. Ozurdex (dexamethasone implant) is a small, biodegradable implant that is injected into the eye. It slowly releases a steroid medication over several months to reduce inflammation and swelling. Ozurdex was approved for RVO-related macular edema in 2009.
Steroid treatments carry some risks, including increased eye pressure and a higher chance of developing cataracts (clouding of the eye's natural lens). A retina specialist will monitor eye pressure closely if a steroid implant is used.
Laser photocoagulation (thermal laser treatment applied to the retina) was once the standard treatment for BRVO with macular edema. While anti-VEGF injections have largely replaced laser as a first-line treatment, laser may still be used in certain situations. For example, laser can help seal off areas of the retina that are not receiving blood flow, which may reduce the drive for abnormal blood vessel growth. In some cases, laser is combined with anti-VEGF therapy.
Treatment options for retinal artery occlusions are more limited. There is currently no widely proven treatment that can reliably restore vision after CRAO, especially if several hours have passed since the blockage occurred. Some emergency measures that may be attempted include ocular massage, medications to lower eye pressure, and in certain cases, clot-dissolving drugs. The most important step after a retinal artery occlusion is a thorough cardiovascular evaluation to reduce the risk of stroke and other life-threatening events.
Research continues to advance the treatment of retinal vascular occlusions. Biosimilar medications, such as ranibizumab-nuna (approved in 2021), offer additional options for anti-VEGF therapy. Preliminary research presented at the ASRS 2025 meeting suggests that GLP-1 receptor agonists, a class of medications used for diabetes and weight management, may reduce the risk of retinal vein occlusion. These findings are still early and require further study.
What to Expect
Most patients with retinal vein occlusion will need a series of intravitreal injections. The procedure is performed in the retina specialist's office. The eye is numbed with anesthetic drops, the surface is cleaned, and a very thin needle is used to inject the medication into the eye. The injection itself takes only a few seconds. Some patients feel pressure or mild discomfort during the procedure. Afterward, mild soreness and temporary floaters are common.
Treatment often begins with a loading phase of monthly injections for the first few months. After that, the retina specialist will evaluate how the eye is responding and adjust the treatment schedule. Some patients can gradually extend the time between injections, while others may need ongoing monthly treatments.
The visual outcome depends on several factors, including the type and severity of the occlusion, how quickly treatment begins, and the overall health of the retina. Many patients with BRVO recover a significant amount of vision with prompt anti-VEGF treatment. CRVO outcomes are more variable, particularly in cases with significant ischemia.
For retinal artery occlusions, the prognosis for vision recovery is generally more guarded. The retina is very sensitive to a lack of oxygen, and permanent damage can occur quickly. Early intervention offers the best chance, but outcomes vary widely.
Retinal vascular occlusions require ongoing monitoring, even after the initial treatment phase. The retina specialist will schedule regular follow-up visits that include OCT imaging and dilated eye exams to watch for recurrent macular edema, new abnormal blood vessel growth, or complications in the other eye. Many patients need treatment over months to years, and some may require periodic injections indefinitely to maintain their vision.
Living With Retinal Vascular Occlusions
Because retinal vascular occlusions are closely tied to conditions like high blood pressure, diabetes, and high cholesterol, managing these underlying health issues is essential. Working with a primary care doctor to keep blood pressure, blood sugar, and cholesterol levels under control can help protect both your eyes and your overall health. If you smoke, quitting is one of the most important steps you can take to reduce your risk of further vascular events.
Some patients experience lasting changes in their vision after a retinal vascular occlusion. This may include reduced sharpness, blind spots, or difficulty with tasks like reading and driving. Low vision rehabilitation services can help patients learn strategies and use assistive devices to make the most of their remaining vision. A retina specialist can provide referrals to these services when appropriate.
Sudden vision loss can be frightening and stressful. It is normal to feel anxious, frustrated, or sad about changes in your vision. Support from family, friends, and patient support groups can make a meaningful difference. Do not hesitate to talk to your doctors about how vision changes are affecting your daily life and mental health.
When to See a Retina Specialist
Certain symptoms require immediate medical attention. See a retina specialist or go to the emergency room immediately if you experience any of the following:
- Sudden, painless loss of vision in one eye
- A dark curtain or shadow moving across your field of vision
- A sudden increase in floaters, especially with flashes of light
- Sudden blurry or distorted vision that does not clear
If you have high blood pressure, diabetes, high cholesterol, or a history of heart disease, regular dilated eye exams are especially important. These exams allow a retina specialist or eye care professional to detect early signs of retinal vascular disease before significant vision loss occurs. Early detection leads to earlier treatment, which generally results in better outcomes.
Questions and Answers
It is possible, though most retinal vascular occlusions affect one eye at a time. Having a vein or artery occlusion in one eye does increase the risk of a future occlusion in either eye. This is one reason why managing cardiovascular risk factors and attending regular follow-up appointments with a retina specialist are so important.
The duration of treatment varies from person to person. Some patients need injections for several months, while others require treatment for years. Newer medications like Vabysmo (faricimab) and Eylea HD (high-dose aflibercept) may allow longer intervals between injections for some patients. A retina specialist will tailor the treatment plan based on how the eye responds at each visit.
Yes. A retinal artery occlusion and a stroke share similar underlying causes, including atherosclerosis and blood clots. Patients who have experienced a CRAO have an increased risk of stroke and other cardiovascular events. This is why a thorough cardiovascular workup, including evaluation of the carotid arteries and heart, is recommended promptly after a retinal artery occlusion is diagnosed.
Visual recovery depends on the type and severity of the occlusion, how much damage occurred before treatment began, and how the eye responds to therapy. Many patients with BRVO see meaningful improvement with anti-VEGF treatment. Patients with severe CRVO or retinal artery occlusions may have more limited recovery. A retina specialist can provide a more personalized outlook based on the findings from your eye exams and imaging tests.
While there is no guaranteed way to prevent these conditions, controlling cardiovascular risk factors significantly lowers your risk. Keeping blood pressure, blood sugar, and cholesterol at healthy levels through diet, exercise, and medication as prescribed by your doctor are the most effective preventive strategies. Avoiding smoking and maintaining a healthy weight also help protect your blood vessels, including those in the eyes.