Central Retinal Artery or Vein Occlusion (Eye Stroke)

How the retina's blood supply works

The central retinal artery enters the eye through the optic nerve and branches across the retina, supplying oxygen to the inner layers. The central retinal vein drains blood out alongside it. The retina is brain tissue: without blood flow, its cells begin to die within about 90 minutes to a few hours.

Blockages can affect the central vessel or one of its branches. Branch occlusions affect part of the visual field. See retinal artery occlusion and branch retinal vein occlusion.

CRAO vs CRVO

Symptoms

CRAO

• sudden, painless loss of most or all vision in one eye
• sometimes preceded by brief episodes of vision loss lasting minutes (amaurosis fugax), a warning sign like a TIA

CRVO

• blurred, dim or distorted vision in one eye
• dark spots or floaters
• often noticed on waking
• vision may fluctuate or worsen over days

Causes and risk factors

• age, most cases occur over 60
• high blood pressure, the strongest risk factor for vein occlusion
• diabetes, high cholesterol and smoking
• atherosclerosis and carotid artery stenosis
• heart conditions: atrial fibrillation and valve disease (sources of emboli for CRAO)
• giant cell arteritis: inflamed arteries in people over 50, causing about 1 in 20 CRAOs
• glaucoma (for CRVO)
• blood disorders: clotting tendencies, high blood viscosity, myeloma
• younger people: clotting disorders, oral contraceptives, inflammatory conditions and dehydration

Diagnosis

An ophthalmologist examines the retina after dilating the pupils and uses:

• optical coherence tomography (OCT) to show retinal swelling and macular edema
• fluorescein angiography to show blood flow and areas without circulation

Because CRAO is a type of stroke, guidelines from the American Heart Association recommend immediate referral to a stroke center for:

• brain MRI, which finds a silent stroke in a significant share of people with CRAO
• imaging of the carotid arteries
• heart rhythm monitoring and an echocardiogram
• blood tests including ESR and CRP to check for giant cell arteritis in people over 50

For CRVO, doctors check blood pressure, blood sugar, cholesterol and eye pressure, and in younger people look for clotting or inflammatory disorders.

Treatment

CRAO

• Emergency evaluation: no treatment has proven to restore vision reliably. Some stroke centers give clot-busting medicine (thrombolysis) within about 4.5 hours of onset, an approach under active study.
• Older measures such as eye massage, lowering eye pressure and breathing carbon dioxide mixtures have not been shown to help.
• Steroids immediately if giant cell arteritis is suspected, to protect the other eye.
• Stroke prevention: antiplatelet medicines, statins, blood pressure control, treatment of atrial fibrillation and carotid surgery where indicated.

CRVO

• Anti-VEGF injections (such as aflibercept, ranibizumab or bevacizumab) into the eye treat macular edema and often improve vision. They are usually given monthly at first.
• Steroid implants in the eye are an alternative.
• Laser treatment (panretinal photocoagulation) if abnormal new blood vessels grow, to prevent neovascular glaucoma.
• Treating risk factors: blood pressure, diabetes, cholesterol and eye pressure.

Outlook

• CRAO: most people have permanent severe vision loss in the affected eye, though a minority recover some vision, especially if blood flow returns quickly or a cilioretinal artery spares the center. The risk of stroke is highest in the first weeks.
• CRVO: outcomes vary. Milder, non-ischemic CRVO can improve, while ischemic CRVO has a poorer outlook. Regular follow-up for several months is needed to catch complications.

Frequently asked questions

What is an eye stroke?

An eye stroke is a blockage of blood flow in the retina, usually a central or branch retinal artery or vein occlusion. Artery occlusions cause sudden, severe vision loss and share risk factors and urgency with brain strokes. Vein occlusions cause blurring and distortion that develop more gradually.

What is the difference between CRAO and CRVO?

CRAO blocks the artery bringing blood into the retina, causing sudden, profound vision loss and a high risk of stroke. CRVO blocks the vein draining the retina, causing bleeding and swelling with blurred vision. CRVO is more common and more treatable with eye injections.

Is central retinal artery occlusion an emergency?

Yes. CRAO is treated as a stroke. Go to an emergency department with stroke services immediately. Doctors will look for the source of the blockage, check for giant cell arteritis and start treatment to prevent a brain stroke, which is most likely in the following days and weeks.

Can vision come back after a retinal vein occlusion?

Often partly. Anti-VEGF injections or steroid implants reduce macular swelling and improve vision in many people with CRVO. Recovery depends on the severity and how much of the retina lost circulation. Ongoing monitoring helps prevent complications such as glaucoma.

What causes a retinal vein occlusion?

The main risk factors are high blood pressure, diabetes, high cholesterol, glaucoma, smoking and age. A hardened artery can compress the neighboring vein where they cross, triggering a clot. In younger people, clotting disorders and inflammatory diseases may be involved.