The eyes, as all the body's organs, depend on the flow of oxygen-rich blood to function.

They have nerves and tissues that send signals to the brain to create a visual image. One of these critical tissues is the retina, which is at the back of the eye.

The retina plays a crucial role in sending visual signals to the brain, and it contains small and large arteries and veins that move blood to and from the heart.

This blood is essential to vision, and a blockage in the retina's blood vessels can permanently affect vision and lead to blindness.

An eye stroke, also known as retinal artery occlusion, is caused by a clot, or narrowing of the retina's blood vessels. The retina's blood flow is interrupted and, if left untreated, can result in permanent damage to the retina and loss of sight.

What is an eye stroke?

During an eye stroke, the retina's veins or arteries stop working as they should. They become blocked by a clot or a narrowing of the blood vessel.

Much like a cerebral stroke, where blood to the brain is reduced or cut off, the retinas in the eye lose their blood supply. Blood and fluid may spill out into the retina and cause swelling. Both the retinas and a person's eyesight can rapidly become damaged.

There are several different types of eye strokes, depending on the blood vessel that is affected:

• Central retinal vein occlusion (CRVO): The retina's main vein becomes blocked.
• Central retinal artery occlusion (CRAO): The retina's central artery becomes blocked.
• Branch retinal vein occlusion (BRVO): The retina's small veins become blocked.
• Branch retinal artery occlusion (BRAO): The retina's small arteries become blocked.

Am I at risk of an eye stroke?

Certain people may have a higher risk than others of having an eye stroke. The risk factors are similar to those of a regular stroke.

Those who have a personal or family history of the following conditions may have a higher risk:

• atherosclerosis, or plaque buildup in the arteries
• high blood pressure
• high cholesterol
• previous heart attack or stroke
• chest pain
• coronary heart disease
• diabetes or a family history of diabetes
• glaucoma

The American Academy of Ophthalmology say that people in their 60s may have the highest risk for an eye stroke, especially men.

Symptoms

An eye stroke is usually painless. A sudden change in a person's vision or loss of vision in one eye is often the first symptom of an eye stroke.

Vision loss can affect the entire eye, or be subtler than that. Some people experience a loss of peripheral vision only or have blind spots or "floaters." Blurry or distorted vision is also possible. Vision changes can start out mild, then become worse over several hours or days.

A cerebral stroke, which affects blood flow to the brain, can also cause sudden vision loss or changes in vision. For this reason, any sudden changes to vision require emergency medical attention.

The longer any stroke is left untreated, the more likely it is that the affected organs will be permanently damaged.

Diagnosing an eye stroke

Sudden vision loss is a medical emergency.

To diagnose an eye stroke, doctors may have to perform tests to see the retina of the eye. These may include:

• Dilating the eyes with drops to see the retina more easily.
• Using a dye and a camera to take pictures of the retina, known as fluorescein angiography. The dye is injected via the arm and allows the doctor to see the retina's veins and arteries more clearly.
• Checking pressure inside the eye using a puff of air.
• Slit-lamp examination, which uses eye drops, a special light, and a microscope to examine the inside of the eyes.
• Vision tests, such as reading eye charts and checking side or peripheral vision.

These tests are painless and are performed by an eye doctor, known as an ophthalmologist.

Treatment

Treatment for an eye stroke should be given as soon as possible, to help minimize damage to the retina. Treatment options include:

• medicines that dissolve blood clots
• a procedure that helps move the clot away from the retina
• widening the arteries in the retina with an inhaled gas

People may also need long-term follow-up care to treat heart disease or blood vessel problems that may have contributed to the eye stroke.

Preventing an eye stroke

Having tests for heart disease is a key part of preventing an eye stroke. This may include regular cholesterol and blood pressure checks, and discussing other risk factors for heart disease, such as family history, diet, and lifestyle.

Heart disease risk factors have a role in the risk for eye strokes. An article in the journal Eye states that 64 percent of people had at least one new, undiagnosed heart disease risk factor that was found after they had an eye stroke. The biggest factor for these individuals was high cholesterol.

In general, to keep blood vessels healthy and help prevent eye stroke, people should:

• get regular exercise; the Physical Activity Guidelines for Americans recommend 2.5 hours a week
• eat a heart-healthy diet, including plenty of fruits, vegetables, whole grains, and unsaturated fats
• work with a dietician, as recommended for some individuals
• avoid or quit smoking
• work with a doctor to manage other health conditions, such as diabetes

Outlook

The long-term outlook for people with eye stroke can vary widely. It depends on the severity of the stroke, the success of treatment, and the arteries or veins that were affected.

The article in the journal Eye, as mentioned above, found that 80 percent of people who had an eye stroke had significant vision loss of 20/400 or worse.

In some cases a person may regain some of their vision over time. A study in the American Journal of Ophthalmology found that vision loss can improve in many people, depending on the type of eye stroke they had.

The authors say that identifying the type of eye stroke is an important factor in how well a person may be able to see afterward.

Conclusion

Following a heart-healthy lifestyle is not just good for the heart. It can improve overall health and reduce the risk of problems, such as eye stroke and vision loss.