Sudden vision loss is a medical emergency

If you lose complete or partial vision in one eye, but are not experiencing any pain, there is a good chance you may be having an ocular stroke, also called a retinal artery occlusion. It is a medical emergency and you should call 911 immediately because, just like with a brain stroke, time is of the essence.

“The retina is such a delicate visual organ that it can’t go without blood supply for more than 60 to 90 minutes,” said cardiologist Lawrence McAuliffe, MD, at Cape Cod Healthcare Cardiovascular Center in Hyannis. “The most important thing is prompt treatment and evaluation because there is a window within which things may be able to be done to help out.”

You can have an ocular event in either a vein or an artery, he explained. The consequences are the same but the cause is quite different. A retinal vein occlusion is usually caused by a thrombosis or thickening of the blood. That clogs the vein up and the backflow and resulting pressure cause damage to the retina. Arterial events are usually caused by plaque or a blood clot traveling and lodging in the artery.

The most common cause of retinal artery occlusion is plaque from the carotid artery breaking free and traveling to the retina. That same plaque could more commonly travel to the brain and cause an ischemic stroke.

A Rare Event

Retinal artery occlusion is rare, occurring in only one in 100,000 people but if it does happen it can be life-altering, Dr. McAuliffe said. Part of the reason it is so rare is the pathway to the retina is less obvious than the pathway to the brain. The clot or plaque would have to travel to the right, off of the carotid arteries, to go into your eyes.

“It’s more likely that an embolic event is going to just keep traveling north into your brain than hang a hard right and end up in your eye,” he said. “That’s why the retinal artery occlusion is so rare.”

There are two major events that can occur if you do have an ocular stroke. A complete occlusion of the artery, which is called a central retinal artery occlusion, causes complete blindness. A branch retinal artery occlusion is a blockage in one of the smaller arteries in your eye. That would still cause some visual disturbance but it would be in a smaller area.

Treatment

One of the more common treatments is to give the patient the blood thinner alteplase within four and a half hours, the same as you would a patient with an ischemic stroke. That treatment has a high incidence of bad side effects and has questionable success for ocular strokes, Dr. McAuliffe said. There are also procedures where doctors attempt to relieve the pressure by aspirating excess fluid out of the eye, but that is also of questionable benefit.

“Despite these treatment options, it often doesn’t make a difference,” he said. “It is a more spontaneous return of blood flow, than any intervention we can pursue with it, that improves the vision.”

But it is important to rule out the rare but treatable condition called giant cell arteritis, which is an inflammatory vasculitis. If high doses of steroids are administered promptly, it can result in the return of vision. There are other even rarer conditions due to blood clotting abnormalities that could be resolved with an anti-coagulant, so it is important to try to figure out what caused the event.

Carotid Artery Involvement

“In the end, the goal is just as important to find out what the cause was as opposed to how to best treat it because the most common cause in older folks is carotid artery disease – blockages in the carotids, and identifying that it can be a marker for having subsequent true brain strokes,” Dr. McAuliffe said.

If there is a carotid blockage, that needs to be surgically corrected with surgery or a stent. After that, the patient would be treated with aspirin and Plavix anti-platelet agents to reduce the chance of more plaque breaking off and traveling.

“Most often this is a disorder of older patients that have all of the usual cardiovascular risk factors like smoking, diabetes, high cholesterol and hypertension,” he said. “All those disorders need to be treated aggressively to prevent future events.”