Retinal Vein Occlusion

What happens in retinal vein occlusion?

The retina has one main artery and one main vein entering and leaving at the optic nerve, plus branches spreading across it. Where an artery crosses a vein, they share a sheath. When the artery hardens and thickens with age and high blood pressure, it can squeeze the vein underneath, slowing blood flow so a clot forms.

Blood then backs up in the retina. The veins swell and leak blood and fluid. Two problems follow:

• Macular edema: fluid collects in the macula, the central area used for reading and faces. This is the main cause of vision loss in RVO.
• Ischemia: parts of the retina starved of oxygen release a growth factor called VEGF, which drives fragile new blood vessels (neovascularization). These can bleed into the eye or block fluid drainage, causing a painful form of glaucoma.

Types of retinal vein occlusion

See branch retinal vein occlusion for details on that type. Retinal vein occlusion is sometimes called an "eye stroke", a term also used for retinal artery occlusion, which is a different and more urgent problem. The page on central retinal artery or vein occlusion compares the two.

Symptoms

• sudden, painless blurred or lost vision in one eye
• vision that worsens over hours or days
• a dark area or blind spot in part of the visual field (BRVO)
• distorted vision, where straight lines look wavy
• floaters if there is bleeding into the vitreous

Some people with a small branch occlusion notice nothing, and it is found at a routine eye exam. Pain is unusual unless glaucoma develops later.

Causes and risk factors

• age: most cases are after 60
• high blood pressure, the strongest modifiable risk factor
• diabetes
• high cholesterol
• glaucoma or raised eye pressure, especially for CRVO
• smoking
• obesity and sleep apnea
• kidney disease

In people under 50, or with occlusions in both eyes, doctors also look for blood-clotting disorders, very high blood counts, inflammatory diseases and the use of estrogen-containing contraceptives.

How it is diagnosed

• Dilated eye exam: shows swollen, twisted veins and flame-shaped hemorrhages. CRVO has a characteristic "blood and thunder" appearance.
• Optical coherence tomography (OCT): a quick, painless scan that measures macular edema and guides treatment.
• Fluorescein angiography: dye injected into an arm vein shows areas of poor blood flow and leakage.
• OCT angiography: a dye-free alternative.
• General health checks: blood pressure, blood sugar, cholesterol, kidney function and a complete blood count, often through your primary care doctor.

Treatment

There is no treatment that reopens the vein. Treatment aims to reduce swelling, prevent complications and protect the other eye.

Treating macular edema

• Anti-VEGF injections (such as aflibercept, ranibizumab, bevacizumab and faricimab) are first-line. They are given into the eye under local anesthetic drops, usually monthly at first, then spaced out. Many people gain several lines on the eye chart.
• Steroid implants or injections (dexamethasone implant or triamcinolone) last several months but can raise eye pressure and speed up cataract.
• Laser (grid laser) is still used for some persistent BRVO swelling.

Treating new blood vessels

Panretinal laser photocoagulation treats the oxygen-starved retina so it stops producing VEGF, lowering the risk of bleeding and neovascular glaucoma. Anti-VEGF injections also help. Vitrectomy surgery removes non-clearing vitreous bleeding.

Treating the risk factors

Controlling blood pressure, diabetes, cholesterol and eye pressure, and stopping smoking, lower the risk of an occlusion in the other eye and of heart attack and stroke, which are more common in people who have had an RVO.

Outlook and recovery

• BRVO: many people regain good vision, especially with treatment. Some recover without injections.
• Non-ischemic CRVO: outcomes are moderate to good with injections, though some convert to the ischemic type.
• Ischemic CRVO: vision often remains poor, and close monitoring for neovascular glaucoma is needed for at least 6 months.

Most people need follow-up and injections for 1 to 2 years. Roughly 1 in 10 people develop an RVO in the other eye over time.

Frequently asked questions

What are the symptoms of retinal vein occlusion?

The main symptom is sudden, painless blurring or loss of vision in one eye. It may be partial, like a shadow or blind spot, or affect the whole eye. Vision may also look distorted or wavy. Some small occlusions cause no symptoms.

What causes retinal vein occlusion?

Most often, a hardened retinal artery compresses a vein where they cross, and a clot forms. High blood pressure, age, diabetes, high cholesterol, glaucoma and smoking increase the risk. Clotting and inflammatory disorders are looked for in younger people.

Can vision come back after retinal vein occlusion?

Often, at least partly. Eye injections reduce macular swelling, and many people with branch occlusions regain good vision. Central occlusions have a more variable outcome, and vision may remain reduced if the retina was starved of blood.

Is retinal vein occlusion a stroke?

It is sometimes called an eye stroke, but it is not a brain stroke. However, it shares the same risk factors, and people who have had an RVO have a higher risk of heart attack and stroke, so blood pressure, cholesterol and blood sugar should be checked.

What is the difference between CRVO and BRVO?

CRVO is a blockage of the main retinal vein and affects the whole retina, often causing more severe vision loss. BRVO is a blockage of a smaller branch and affects only part of the retina. BRVO is more common and usually has a better outlook.