Central Retinal Artery Occlusion
CRAO is a blockage of the main artery in the retina, the light-sensitive nerve layer at the back of the eye. The first sign of CRAO is a sudden and painless vision loss that leaves one barely able to count fingers or determine light from dark.
Central retinal artery occlusion usually occurs in people between the ages of 50 and 70. There are several ways that this can happen. The most common is embolic – blockage of the artery from a clot that breaks off from the carotid artery, the artery in the neck that supplies blood to the brain and the eye. This is literally a stroke in the eye and needs to be addressed as such. Patients are at a high risk for a bigger stroke. A full vascular work-up is important to prevent stroke and also heart attacks. It is less common for the embolus to be from the heart, but the heart needs to be studied, too. A second mechanism is that the artery can be choked off from hardening (atherosclerosis) of the central retinal artery. Again, a full vascular work-up is in order, addressing risk factors of atherosclerosis, such as hypertension (high blood pressure), high cholesterol, obesity, and smoking.
Third, the artery can be blocked by inflammation in a condition known as temporal arteritis or giant cell arteritis. Ruling out giant cell is a critical emergency. The inflammation is not restricted to the affected artery but affects all of the medium-sized arteries in the body. You can go blind in the other eye, unless steroid treatment is started now! In the case of a CRAO your doctor will send you for stat blood work and have you take steroids, pending the outcome of the blood work. If the blood work is abnormal, you will be asked to stay on the steroid pills, pending the outcome of a temporal artery biopsy, a simple outpatient procedure.
Loss of vision is usually permanent without immediate treatment. Irreversible retinal damage occurs after 90 minutes. Some centers now treat CRAO with intravenous clot-busting drugs. This treatment may cause some improvement in the vision, if started within six hours of onset. The goal of emergency treatment is to restore retinal blood flow. After emergency treatment, you should have a thorough medical evaluation.