What Is Eye Stroke?
An eye stroke, or anterior ischemic optic neuropathy, is a dangerous and potentially debilitating condition that occurs from a lack of sufficient blood flow to the tissues located in the front part of the optic nerve. (If the blockage occurs as the blood vessels emerge out of the optic nerve and onto the retina, it is called a central or branch retinal artery occlusion.) An eye stroke can cause sudden loss of vision.
Causes of Eye Stroke
Eye stroke is caused by poor circulation in the blood vessels that supply the front portion of the optic nerve. The optic nerve is the cable that connects the brain to the eye and carries millions of nerve fibers and blood vessels. Although an eye stroke can occur from a total blockage of a blood vessel that feeds the optic nerve, it is more commonly caused by a lack of pressure or perfusion of the tissue. Blood pressure may change relative to the eye pressure and the normal flow of blood is reduced. If the optic nerve's nutrient and oxygen supply is cut off, nerve tissue is damaged and lost, resulting in vision loss.
Symptoms of Eye Stroke
People with eye stroke are usually given little warning. Most people with eye stroke notice a loss of vision in one eye upon waking in the morning with no pain. Some people notice a dark area or shadow in their vision that affects the upper or lower half of their visual field. Other symptoms include loss of visual contrast and light sensitivity.
Risk Factors of Eye Stroke
Eye stroke is more common in middle-aged people and the elderly. Approximately 10% of patients that are affected with anterior ischemic optic neuropathy are under the age of 45. Cardiovascular disease raises your risk for developing the disease. In some patients with cardiovascular disease, blood pressure falls markedly while sleeping. This low blood pressure reduces circulation through those arteries, increasing the chance of eye stroke. Some physicians feel that newer, more powerful anti-hypertensive medications may reduce blood pressure too low when sleeping, putting people at risk for eye stroke.
Certain optic disc shapes can also raise your risk of eye stroke. Nerve fibers that travel to the brain and down the optic nerve must enter the eye through a hole called the optic foramen. If this hole is smaller than average, the nerve fibers can become crowded. When they become crowded, the risk of developing an occlusion increases. Although the relationship is not well understood, people who have significant cardiovascular disease and also take the drug Viagra, are more at risk for the disease.
Diagnosis of Eye Stroke
If your doctor suspects eye stroke, he or she will review your medical history and ask about cardiovascular disease and conditions you may have such as diabetes, hypertension or high cholesterol. Your blood pressure will be measured as well as your central visual acuity and visual field. Your doctor will usually dilate your eyes to exam your optic nerve and retina. Your doctor will also examine your optic nerve to check for pale color or possibly optic disc swelling.
Your normal eye will be compared to the affected eye to detect changes. Your doctor will also carefully rule out artertic ION (a serious eye stroke affecting the optic nerve) and ask about symptoms such as fever, headache, scalp tenderness, jaw pain, weight loss, loss of appetite and fatigue. (Artertic ION is life-threatening and is always considered.)
Treatment at Penn
Corticosteroids have been shown to increase visual acuity in some cases of eye stroke if started early enough. Corticosteroids reduce leakiness of the vessels and improve swelling and circulation. Corticosteroids are the treatment of choice in AION because it is an eye stroke that appears to be more commonly caused by reduced blood flow and inflammation, as opposed to a true blockage of a blood vessel from a small particle, or emboli. Some doctors prescribe drugs to lower eye pressure in hopes to improve blood flow to the optic nerve.
There has been some research on the potential to prescribe medications that act as neuro-protection that may regenerate nerve fibers in the optic nerve. However, there is no conclusive evidence that these drugs provide any benefit. Other treatment is aimed at controlling cardiovascular risk factors so eye stroke does not occur to the other eye, as there is a 30% chance that it will happen to the other eye within three years.