Retinal Artery Occlusion (RAO)

The task of bringing oxygen and nutrients to the retina primarily falls to the central retinal artery (CRA) and its branches. When this artery or its branches get partially blocked or occluded due to a retinal embolism (a small piece of cholesterol that blocks blood flow), thrombus (blood clot), atherosclerosis, or arteritis, it can result in varying degrees of vision loss. The retinal artery occlusion may be transient and last for only a few seconds or minutes if the blockage breaks up and restores blood flow to the retina, or it may be permanent.

Retinal Artery Occlusion Symptoms

Retinal artery occlusion is usually associated with sudden painless loss of vision in one eye. The area of the retina affected by the blocked vessels determines the area and extent of visual loss.

• The main artery supplying blood to the eye is the ophthalmic artery; when it is blocked, it produces the most damage. A blockage in the main artery in the retina is called central retinal artery occlusion (CRAO), which often results in severe loss of vision. However, about 25% of people who develop CRAO have an extra artery called a cilioretinal artery in their eyes. When CRAO occurs, having a cilioretinal artery can greatly lessen the chances of damage to your central vision, as long as the cilioretinal artery is not affected.
• A blockage in a smaller artery is called branch retinal artery occlusion (BRAO); this may cause a loss of a section of your visual field, such as your vision to one side. If the affected area is not in the center of the eye or is relatively small, a BRAO may go unnoticed with no symptoms.

Common risk factors include:

• Carotid artery disease
• Artherosclerosis (fatty deposits in the arteries)
• Faulty heart valves (valvular heart disease)
• Tumors in the heart (myxoma)
• Abnormal heart rhythms such as atrial fibrillation
• Diabetes
• High blood pressure
• Intravenous drug abuse
• Giant-cell arteritis
• Disorders contributing to blood clot formation, such as sickle cell disease
• Use of oral contraceptives
• Homocystinuria (a hereditary disorder that prevents your body from processing the amino acid methionine; this leads to an excess accumulatio of homocysteine in the blood and urine)
• Pregnancy
• Blood platelet abnormalities

Most retinal artery occlusion patients are in their 60s and are more commonly men than women.

The need for timely care

Unfortunately, there is no clinically proven treatment for CRAO.

Persons with an acute onset CRAO or BRAO are referred promptly to the emergency room or their primary care doctor to be evaluated for stroke risk. An important aspect of managing retinal artery occlusion is for your primary doctor to identify and manage risk factors that may lead to other vascular conditions. The risk factors for CRAO are the same atherosclerotic risk factors as for stroke and heart disease.

Formation of new blood vessels of the retina or iris that are prone to bleed is a rare complication seen after a CRAO or BRAO. Growth of these vessels can further decrease vision by causing vitreous hemorrhage and glaucoma. Intraocular injections and/or laser photocoagulation therapy may need to be used in such cases.