What Is Retinal Vein Occlusion?
Retinal vein occlusion (RVO) occurs when one of the veins that carries blood away from the retina becomes blocked, typically by a blood clot or compression from a nearby hardened artery. The blockage disrupts normal blood flow, causing blood and fluid to back up into the retina. This leads to hemorrhages (bleeding), swelling, and oxygen deprivation in the affected area.
RVO is the second most common retinal vascular disease after diabetic retinopathy, affecting approximately 16 million people worldwide. Vision loss results primarily from macular edema (fluid accumulation at the center of the retina), which is highly treatable, and from retinal ischemia (oxygen deprivation), which causes permanent damage.
Types of Retinal Vein Occlusion
Branch Retinal Vein Occlusion (BRVO)
BRVO is the more common form, accounting for about 75% of all cases. It occurs where a retinal artery crosses over and compresses a branch vein, blocking blood flow in one section of the retina. Vision loss typically affects part of your visual field rather than your entire eye. BRVO generally has a favorable prognosis with treatment — approximately 70% of treated patients achieve 20/40 or better (driving vision) by one year. Some cases improve on their own, though significant improvement beyond 20/40 is uncommon without treatment.
Central Retinal Vein Occlusion (CRVO)
CRVO accounts for about 25% of cases and is more serious. The blockage occurs in the main retinal vein, affecting the entire retina. CRVO causes more widespread bleeding and swelling, and carries a higher risk of complications. It is further classified as non-ischemic (about 70% of cases, with a moderate prognosis) or ischemic (about 30%, with a poorer outlook). Up to 34% of initially non-ischemic CRVO cases can progress to the ischemic form over time, which is why ongoing monitoring is essential.
| Feature | BRVO | CRVO |
| Retinal area affected | One section (typically one quadrant) | Entire retina (all four quadrants) |
| Proportion of all RVO | ~75% | ~25% |
| Vision loss pattern | Partial visual field loss, sectoral blurring | Diffuse blurring or complete central vision loss |
| Overall prognosis | Generally favorable with treatment | Variable; depends on ischemic classification |
Common Symptoms
Retinal vein occlusion typically causes sudden, painless changes in vision. The painless nature of the condition is important to understand — because there is no pain, patients sometimes attribute their symptoms to fatigue or aging and delay seeking care.
- Sudden blurring of vision in one eye, which may develop over hours or be noticed abruptly upon waking.
- A dark or missing area in part of your visual field.
- Distorted vision — straight lines appearing wavy or bent — caused by macular swelling.
- Colors appearing washed out or faded.
- Floaters, which may indicate bleeding from abnormal blood vessel growth in advanced cases.
Seek immediate evaluation if you experience: sudden severe or complete vision loss in one eye, or eye pain accompanied by vision loss and redness (which may indicate neovascular glaucoma, a serious complication requiring same-day treatment).
Causes and Risk Factors
Retinal vein occlusion is caused by a blockage in the retinal venous system, typically when a nearby artery, stiffened by atherosclerosis (hardening of the arteries), compresses the vein and creates conditions for a blood clot to form. The underlying risk factors are the same conditions that increase the risk of heart disease and stroke.
- High blood pressure: The strongest risk factor for RVO, present in approximately 68% of patients.
- High cholesterol: Carries roughly twice the risk of RVO compared to normal levels.
- Diabetes: Particularly associated with BRVO due to its effects on blood vessel walls.
- Age: Risk increases significantly with age; over 90% of CRVO patients are older than 50.
- Glaucoma or elevated eye pressure: Particularly for CRVO, where increased pressure compromises venous drainage.
- Smoking and obesity: Established vascular risk factors that increase RVO risk.
- Blood clotting disorders: More relevant in patients under 50, where inherited thrombophilia is found in about 32% of cases.
Important: Every patient diagnosed with RVO should have a medical workup for underlying cardiovascular risk factors. Identifying and managing these conditions reduces the risk of RVO in your other eye and your overall cardiovascular risk.
How Is Retinal Vein Occlusion Diagnosed?
RVO is diagnosed through a comprehensive dilated eye examination. At Retina Vision Consultants, we use advanced imaging to assess the type and severity of your occlusion, guide treatment decisions, and monitor your response over time.
- Optical Coherence Tomography (OCT): The primary tool for detecting and measuring macular edema. OCT provides high-resolution cross-sectional images of the retina and is used at every visit to track treatment response.
- Fluorescein Angiography (FA): The gold standard for assessing retinal ischemia. A dye is injected into your arm and photographs are taken as it flows through the retinal blood vessels, revealing areas of poor blood flow and abnormal vessel growth. FA is critical for classifying your RVO as ischemic or non-ischemic, which directly affects your prognosis.
- OCT-Angiography (OCTA): A non-invasive, dye-free technique that maps the retinal blood vessels in fine detail. OCTA can identify macular ischemia and early abnormal vessel growth.
- Fundus Photography: High-detail images documenting the extent of hemorrhage and retinal involvement, used for baseline comparison and monitoring.
Treatment Options at RVC
The primary cause of vision loss in RVO — macular edema — is highly treatable, and early treatment is associated with the best visual outcomes. Treatment cannot reverse ischemic damage that has already occurred, but it can resolve swelling, prevent further vision loss, and in many cases significantly improve your visual acuity.
Anti-VEGF Injections (First-Line Treatment)
Anti-VEGF medications (such as Eylea®, Vabysmo®, Lucentis®, or Avastin®) are the current first-line treatment for macular edema from both BRVO and CRVO. These injections block the protein (VEGF) that drives fluid leakage and abnormal blood vessel growth. In clinical trials, more than half of treated patients gained three or more lines of vision within six months. Treatment typically begins with monthly injections during a loading phase, then transitions to longer intervals as your eye responds. Most patients receive 6–8 injections in the first year.
Corticosteroid Implant (Second-Line)
For patients who do not respond adequately to anti-VEGF injections, or who cannot maintain the frequent visit schedule required, a sustained-release dexamethasone implant (Ozurdex®) can be placed inside the eye to reduce macular swelling for approximately 3–4 months. This option is particularly suited for patients who have already had their natural lens replaced (pseudophakic), as it carries a risk of cataract progression and elevated eye pressure that require monitoring.
Laser Photocoagulation
Laser treatment has a more limited role than in the past but remains useful in specific situations. Panretinal photocoagulation (PRP) is used when ischemic RVO leads to the growth of abnormal blood vessels, which can cause serious complications including neovascular glaucoma. Focal laser may be used alongside anti-VEGF therapy to help reduce injection frequency in some BRVO patients.
Living With Retinal Vein Occlusion: What to Expect
Will my vision recover? In many cases, yes — particularly with prompt treatment. In clinical trials, approximately 70% of treated BRVO patients achieved driving-level vision (20/40 or better) by one year. CRVO outcomes are more variable and depend heavily on whether the occlusion is ischemic or non-ischemic. Even with successful treatment of macular edema, the degree of underlying retinal ischemia sets a ceiling on how much vision can be recovered.
How long will I need treatment? Active anti-VEGF treatment typically continues for 12–24 months, though some patients need ongoing treatment beyond two years. Monitoring continues even after injections stop, because macular edema can recur and the condition can progress from non-ischemic to ischemic forms months or years later.
What about my other eye? BRVO patients have approximately a 10% risk of developing RVO in the fellow eye within three years; CRVO patients have about a 1% risk per year. The best way to reduce this risk is to manage the underlying conditions that caused the first event — particularly blood pressure, cholesterol, and blood sugar — in close coordination with your primary care doctor.
When to See a Retina Specialist
Any sudden, painless blurring, darkening, or missing area in your vision should be evaluated promptly — ideally within 24–48 hours. If you experience sudden severe vision loss in one eye, or eye pain with vision loss and redness, seek evaluation the same day.
Call Retina Vision Consultants at (310) 269-8565 to request an appointment. Early treatment gives you the best chance of recovering and preserving your vision.
