Branch Retinal Vein Occlusion (BRVO)

What happens in BRVO

The retina receives blood through the central retinal artery and drains it through the central retinal vein, both of which branch across the retina. Inside the eye, arteries and veins cross and share a common sheath. When the artery wall stiffens and thickens, typically from high blood pressure or atherosclerosis, it can compress the vein at the crossing point. Blood flow slows, a clot forms, and the vein is blocked.

Blood backs up behind the blockage. This causes:

• bleeding into the retina, seen as flame-shaped hemorrhages in a wedge pattern
• macular edema: fluid leaking into the macula, the center of vision, the main cause of vision loss in BRVO
• ischemia: parts of the retina starved of oxygen, which can trigger abnormal new blood vessels (neovascularization)

BRVO is about three to four times more common than a central retinal vein occlusion, which blocks the main vein and affects the whole retina. See central retinal artery or vein occlusion.

Symptoms

• sudden, painless blurred vision in one eye
• a dark area or missing section of vision, often in the upper or lower half
• wavy or distorted lines if the macula is swollen
• floaters if bleeding has reached the vitreous gel

If the blocked branch does not drain the macula, there may be no symptoms, and BRVO is discovered at a routine eye exam.

Causes and risk factors

• High blood pressure: the strongest risk factor
• Age over 60
• Diabetes
• High cholesterol and atherosclerosis
• Glaucoma or raised eye pressure
• Smoking
• Obesity and sleep apnea
• Blood clotting or thickening disorders, especially in younger people: high homocysteine, antiphospholipid syndrome, polycythemia, and some leukemias
• Medicines such as estrogen-containing contraceptives in some people

Diagnosis

An eye doctor will check your vision and eye pressure and examine the retina after dilating drops. Tests include:

• OCT (optical coherence tomography): a scan that measures macular swelling and guides treatment
• fluorescein angiography: dye injected into an arm vein shows blocked areas, leaking vessels and ischemia
• OCT angiography in some clinics

Because BRVO signals vascular disease, your eye doctor will usually ask your primary care doctor to check:

• blood pressure
• blood sugar (HbA1c) and cholesterol
• blood count
• clotting tests in people under 50 or without obvious risk factors

Treatment

There is no treatment that reopens the blocked vein. Treatment targets the complications.

Macular edema

• Anti-VEGF injections (ranibizumab, aflibercept, bevacizumab, faricimab): medicines injected into the eye that block the signal causing leakage. They are the first-line treatment, usually started with monthly injections, then spaced out as the edema settles. Many people gain significant vision.
• Steroid implants (dexamethasone implant) or injections: an alternative or add-on, especially if anti-VEGF response is incomplete. They can raise eye pressure and speed cataract formation.
• Focal or grid laser: used less often now, sometimes for persistent edema.

The injection is done in the clinic with numbing drops and takes seconds. Most people feel pressure rather than pain.

Abnormal new vessels

If ischemia leads to new blood vessels, scatter laser photocoagulation to the affected area reduces the risk of vitreous hemorrhage. Surgery (vitrectomy) may be needed for a bleed that does not clear.

Control risk factors

Treating blood pressure, diabetes, cholesterol and eye pressure, and stopping smoking, lowers the risk of another occlusion in either eye and protects general health.

Outlook

Some people with mild BRVO recover good vision without treatment as collateral vessels form. With anti-VEGF treatment, many people with macular edema regain several lines of vision on the eye chart. Outcomes are better when treatment starts early. About 1 in 10 people develop a vein occlusion in the other eye over the following years, which is why controlling risk factors matters.

Complications

• persistent macular edema
• vitreous hemorrhage from new vessels
• retinal detachment (rare)
• neovascular glaucoma (much less common in BRVO than in central vein occlusion)

Frequently asked questions

What are the symptoms of branch retinal vein occlusion?

BRVO usually causes sudden, painless blurring, a dark patch or distortion in part of the vision of one eye. Some people notice floaters. If the blockage is away from the center of the retina, there may be no symptoms.

What causes branch retinal vein occlusion?

Most BRVOs happen where a stiff, thickened artery crosses and squeezes a retinal vein, leading to a clot. High blood pressure is the main risk factor. Age, diabetes, high cholesterol, glaucoma and smoking also increase risk.

Can vision return after BRVO?

Often, yes. Vision improves in many people, either on its own as new drainage pathways form or with anti-VEGF injections that reduce macular swelling. Starting treatment early gives the best chance of recovery.

Is branch retinal vein occlusion a stroke?

It is sometimes called an "eye stroke", but it is a blocked vein, not a blocked artery or brain stroke. It does share risk factors with stroke and heart disease, so blood pressure, cholesterol and blood sugar should be checked after diagnosis.

How many injections are needed for BRVO?

It varies. Treatment usually starts with monthly injections for about 3 months, then the interval is extended based on OCT scans. Many people need injections for 1 to 2 years, and some stop sooner once the swelling resolves.