Central retinal vein occlusion (CRVO) is an eye condition that affects the retina — the light-sensitive layer of tissue in the back of your eye. It happens when a blood clot blocks the main vein where blood flows out of the retina. It usually only affects 1 eye.

Some people don’t have any symptoms, but many people with CRVO have blurry vision. The good news is that getting treatment early can help lower the chance of vision loss.

There are 2 types of CRVO:

• Non-ischemic — a mild type of CRVO that causes blood vessels in the retina to leak
• Ischemic — a severe type of CRVO that reduces or blocks blood flow to blood vessels in the retina

Most people with this condition have mild CRVO, but it can turn into severe CRVO without treatment.

There’s another type of retinal vein occlusion called branch retinal vein occlusion (BRVO). BRVO is similar to CRVO, but it affects the smaller veins in the retina — not the main vein.

Adults age 50 or older are more likely to have CRVO. You may also be more likely to develop CRVO if you have:

• High blood pressure
• Diabetes
• Glaucoma
• Arteriosclerosis (hardening of the arteries)

CRVO and glaucoma

Experts don’t know the exact causes of CRVO or glaucoma, but they do know that CRVO and glaucoma are connected.

The causes of CRVO aren’t clear. Experts do know that people get CRVO if they have a blood clot or reduced blood flow out of the central retinal vein (the main vein that helps blood flow away from the retina).

When the retina doesn’t get enough blood flow, it also doesn’t get enough oxygen. This causes the release of a protein called vascular endothelial growth factor (VEGF). Too much VEGF can cause swelling in the retina, called macular edema.

Many people with CRVO have blurry vision.

If you have very mild CRVO, you may not have any symptoms. If your CRVO is more severe, you may have pain or redness in your eye. It’s important to talk to an eye doctor as soon as you can if you notice these symptoms — even if they’re mild. Early treatment can help lower the chance of vision loss from CRVO.

Eye doctors can check for CRVO as part of a comprehensive dilated eye exam. The exam is simple and painless — your doctor will give you some eye drops to dilate (widen) your pupil and then check your eyes for CRVO and other eye problems.

Other tests for CRVO include:

• Fluorescein angiogram. In this test, your eye doctor will inject a special dye into your arm. This dye will actually travel from your arm to your eye. Then the doctor will use a camera to take photos of the retinal veins as the dye moves through them.
• Optical coherence tomography (OCT). In this test, your eye doctor will take pictures of your retina with a special machine. This can help your doctor see how much swelling there is. Your eye doctor may also use this test after treatment for CRVO to see how well it’s working.

There’s no cure for CRVO, but treatment can improve your vision or keep your symptoms from getting worse. Catching CRVO early and getting treatment as soon as possible can help lower the chance of vision loss. Treatments include: