A retinal artery occlusion (RAO) is a blockage in one or more of the arteries of your retina. The blockage is caused by a clot or occlusion in an artery, or a build-up of cholesterol in an artery. This is similar to a stroke.

There are two types of RAOs:

• Branch retinal artery occlusion (BRAO) blocks the small arteries in your retina.
• Central retinal artery occlusion (CRAO) is a blockage in the central artery in your retina.

Central  Retinal Vein (Artery) Occlusion

Arteries and veins carry blood throughout your body, including your eyes. The eye’s retina has one main artery and one main vein. When the main retinal vein becomes blocked, it is called central retinal vein occlusion (CRVO).

When the vein is blocked, blood and fluid spills out into the retina. The macula can swell from this fluid, affecting your central vision. Eventually, without blood circulation, nerve cells in the eye can die and you can lose more vision.

The most common symptom of CRVO is vision loss or blurry vision in part or all of one eye. It can happen suddenly or become worse over several hours or days. Sometimes, you can lose all vision suddenly.

You may notice floaters. These are dark spots, lines or squiggles in your vision. These are shadows from tiny clumps of blood leaking into the vitreous from retinal vessels. In some more severe cases of CRVO, you may feel pain and pressure in the affected eye. CRVO almost always happens only in one eye.

Branch Retinal Vein (Artery) Occlusion

Arteries and veins carry blood throughout your body, including your eyes. The eye’s retina has one main artery and one main vein. When branches of the retinal vein become blocked, it is called branch retinal vein occlusion (BRVO).

When the vein is blocked, blood and fluid spills out into the retina. The macula can swell from this fluid, affecting your central vision. Eventually, without blood circulation, nerve cells in the eye can die and you can lose more vision
The most common symptom of BRVO is vision loss or blurry vision in part or all of one eye. It can happen suddenly or become worse over several hours or days. Sometimes, you can lose all vision suddenly.

You may notice floaters. These are dark spots, lines or squiggles in your vision. These are shadows from tiny clumps of blood leaking into the vitreous from retinal vessels.

BRVO almost always happens only in one eye.

BRVO usually happens in people who are aged 50 and older.

People who have the following health problems have a greater risk of BRVO:

• high blood pressure
• diabetes
• glaucoma
• hardening of the arteries (called arteriosclerosis).

To lower your risk for BRVO, you should do the following:

• eat a low-fat diet
• get regular exercise
• maintain an ideal weight
• don’t smoke.