Central Retinal Artery Occlusion / Branch Retinal Artery Occlusion
What is a Retinal Artery Occlusion?
The optic nerve is the highway for the blood supply to and from the eye. Arteries bring blood into the eye and veins carry blood out of the eye. Sometimes the main artery entering the eye (central retinal artery) or a branch of the main artery become blocked. When this occurs the portion of the retina supplied by this artery becomes starved for blood. This process is similar to what happens when someone has a stroke. Without blood flow the affected area of retina fails to function normally and thus patients lose a portion or all of their vision. The loss of vision is typically painless and occurs suddenly. If the main artery feeding the eye becomes blocked, it is called a Central Retinal Artery Occlusion (CRAO). If one of the smaller arteries becomes blocked, it is called a Branch Retinal Artery Occlusion (BRAO).
Why do I have a Retinal Artery Occlusion?
An artery occlusion occurs in most cases because something is blocking the blood flow, similar to an accident causing a traffic jam on a highway. The cause of the blockage most commonly is from a clot or blood or cholesterol plaque from the carotid artery or from the heart. A retinal artery occlusions typically occurs in patients over the age of 60. Additionally patients are at increased risk if they have any of the following conditions:
High Blood Pressure
Cardiac Valvular Disease
An important and less common cause for artery occlusions is ocular inflammation (Giant Cell Arteritis). Giant cell arteritis occurs when the body fails to recognize the artery as a part of itself and attacks the artery. The resulting inflammation blocks the artery and leads to an artery occlusion. Other less common causes of retinal artery occlusions are fat emboli released after bone crushing injury, intravenous drug use and collagen vascular diseases.
In rare instances an artery occlusion may occur in a young healthy patient. In these instances laboratory testing may be indicated to look for a clotting disorder.
Assessment of a Retinal Artery Occlusion
A retinal artery occlusion is typically detected by your eye doctor during a dilated eye exam. The affected retina often looks swollen and discolored, occasionally a plaque is visible in the blocked artery. Your retinal doctor may use Fluorescein Angiography (FA) to determine the extent of the blockage. Additionally visual field testing may be performed to map the extent of the visual field affected.
What Treatment is Available?
Unfortunately, there is no good treatment to restore vision in patients with retinal artery occlusions. Based on animal studies, irreversible damage occurs to retinal tissue within 90 minutes of a blockage. If caught early enough, your doctor may perform ocular massage and remove some fluid from your eye to attempt to dislodge the blockage.
In all cases of artery occlusion it is important that we work with your primary care doctor to arrange for testing to determine the source of the blockage. This may include a carotid doppler ultrasound and cardiac echocardiogram. If an abnormality is found, it is extremely important to identify and treat it as other blood vessels in the brain or eye may become involved and lead to further eye damage or a stroke in the brain.