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Eye Strokes Occlusions What is an eye stroke?
Just as the brain can suffer damage when blood flow is blocked, important structures inside the eye can become injured when an artery or vein within the eye becomes has a blockage (also called an occlusion). This is referred to as an eye stroke.

An eye stroke results in sudden, but painless, vision loss or distorted vision in one eye. The severity of the symptoms depends on where the blockage is located, and how much blood flow is blocked. It is important to seek immediate medical attention, as damage will worsen quickly unless blood flow is restored.

Retinal Artery Occlusion (BRAO and CRAO)
A retinal artery occlusion occurs when an artery to the retina is blocked. The retina is the light-sensitive lining of the back of the eye that records what we see, similar to the film inside a camera.

When the retina becomes damaged, the results can be catastrophic. If it is the central artery that becomes blocked (called a central retinal artery occlusion, or CRAO), the result is usually sudden, total vision loss, though you may retain some peripheral vision. If the blockage occurs in one of the arteries which branch off the central blood vessel (a branch retinal artery occlusion, BRAO), you will experience a sudden loss of peripheral vision, with central vision possibly being affected as well. In both cases, the loss of vision is usually painless.

Retinal artery occlusions are typically caused when a blood clot (or embolus) from the heart or carotid artery in the neck travels to the eye. Certain people are at higher risk for this condition, including those with high blood pressure (hypertension), artery disease (especially in the carotid), heart disease, cholesterol problems, or diabetes.

Techniques used to diagnose a retinal artery occlusion may include a dilated pupil exam or a fluorescein angiogram. Unfortunately, no treatment has been proven effective for this condition, however there are a number of things your doctor may try to dislodge the embolus and restore blood flow including glaucoma medication, removal of some fluid from within the eye (anterior chamber paracentesis), and ocular massage.

Even with prompt treatment, a retinal artery occlusion will likely result in permanent vision damage. With a BRAO, this may include blind spots and distortions, though you will likely retain good central vision. A CRAO will produce more severe vision problems, as it is primarily the central field of vision that is affected.

Other complications may include neovascularization of the retina or iris, neovascular glaucoma, or temporal arteritis.

Retinal Vein Occlusion (BRVO and CRVO)
When a vein within the retina is blocked by a blood clot (thrombus), this is called a retinal vein occlusion. It may be either a branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO), depending on which blood vessel has the blockage.

Retinal vein occlusion is most commonly seen in people with hardening of the arteries (arteriosclerosis), high blood pressure, or glaucoma. Symptoms include sudden, painless vision loss which can be mild or severe and may include blind spots, distorted vision, or loss of peripheral vision.

Diagnosis is usually done with a dilated pupil exam, where the doctor may observe signs such as retinal bleeding. A fluorescein angiogram may also be used, especially if neovascularization is suspected.

One possible treatment for this condition is a laser procedure called pan-retinal laser photocoagulation, though only some people are good candidates. This can help repair some retinal damage.

The prognosis for BRVO and CRVO depends on a number of factors. In general, people who had less vision loss initially have better outcomes than those who begin with severe vision loss. Complications may include neovascularizaion of the retina, optic nerve, or iris; or intractable glaucoma.

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