Doctors typically make the diagnosis by looking in the eye with an ophthalmoscope and sometimes by testing.
Treatments are usually unsuccessful in restoring vision.
The central retinal artery is the main vessel that supplies blood to the retina. This artery can become completely blocked by an embolism or thrombosis (formation of a blood clot in the artery). Blockage may occur in the main artery or in its branches.
An embolism is a collection of solid material that floats in the bloodstream until it gets stuck in and blocks a blood vessel. The material that forms an embolus can come from a piece of atherosclerotic plaque Atherosclerosis Atherosclerosis is a condition in which patchy deposits of fatty material (atheromas or atherosclerotic plaques) develop in the walls of medium-sized and large arteries, leading to reduced or... read more 
from an artery in the neck, fat, infected material from an infected heart valve (endocarditis Infective Endocarditis Infective endocarditis is an infection of the lining of the heart (endocardium) and usually also of the heart valves. Infective endocarditis occurs when bacteria enter the bloodstream and travel... read more 
), or a noncancerous (benign) tumor in a heart chamber (atrial myxoma Myxomas A myxoma is a noncancerous primary heart tumor, usually irregular in shape and jellylike in consistency. People may feel short of breath or faint, or they may have fever or weight loss. Doctors... read more ).
Giant cell arteritis Giant Cell Arteritis Giant cell arteritis is chronic inflammation of large and medium arteries of the head, neck, and upper body. Typically affected are the temporal arteries, which run through the temples and provide... read more , an inflammation of the blood vessels, is also a possible cause of retinal artery blockage.
Sometimes the cause of the blockage is unknown.
Symptoms
The affected eye has a sudden and severe but painless loss of vision over the entire field of vision. Sometimes only a part of the field of vision is affected.
Blockage of the central retinal artery may also cause growth of abnormal blood vessels on the retina or iris. Sometimes these abnormal blood vessels bleed or cause a painful type of glaucoma (called neovascular glaucoma). In neovascular glaucoma, abnormal blood vessels that have formed in the iris close the space between the iris and the cornea, blocking the drainage of fluid from the eye and causing buildup of pressure in the eye (glaucoma Glaucoma Glaucomas are a group of eye disorders characterized by progressive optic nerve damage (often, but not always, associated with increased eye pressure) that can lead to irreversible loss of vision... read more ).
Diagnosis
A doctor's examination of the eye
Fluorescein angiography
Optical coherence tomography
Sometimes echocardiography, Doppler ultrasonography, and/or blood tests
Using an ophthalmoscope, doctors can see changes in blood vessels and the retina. If the central retinal artery is blocked, the retina may appear pale.
Fluorescein angiography Angiography A variety of tests can be done to confirm an eye problem or to determine the extent or severity of an eye disorder. Each eye is tested separately. In general, angiography involves injecting... read more helps determine the extent of damage to the retina and helps the doctor plan treatment. In this procedure, a doctor injects dye into a vein in the arm and then photographs the retina. Optical coherence tomography Optical Coherence Tomography A variety of tests can be done to confirm an eye problem or to determine the extent or severity of an eye disorder. Each eye is tested separately. In general, angiography involves injecting... read more (an imaging study) can help show that the retina is swollen, which is common.
Once retinal artery occlusion has been diagnosed, doctors need to search for a source of an embolus. They do tests such as echocardiography Echocardiography and Other Ultrasound Procedures Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of... read more 
and carotid Doppler ultrasonography Echocardiography and Other Ultrasound Procedures Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of... read more . They may also do blood tests to diagnose giant cell arteritis.
If people experience sudden brief loss of vision in one eye and doctors think this is due to a clot that is blocking the retinal artery, treatment is started immediately rather than delayed for imaging studies.
Prognosis
If the blockage occurred in a branch of the central retinal artery, people may maintain good to fair vision.
If the blockage occurred in the central retinal artery itself, vision loss is often profound, even with treatment.
Once the retinal tissue becomes permanently damaged, which can happen as quickly as 90 minutes after the blockage, vision loss is usually permanent.
If giant cell arteritis Giant Cell Arteritis Giant cell arteritis is chronic inflammation of large and medium arteries of the head, neck, and upper body. Typically affected are the temporal arteries, which run through the temples and provide... read more is the cause of the retinal artery blockage, prompt diagnosis and treatment may allow people to regain some lost vision and be protected from damage to the other eye.
People with retinal artery occlusion may have blockages affecting other arteries that supply the brain. These blockages increase the risk of stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more , particularly in the weeks following a central retinal artery occlusion.
Treatment
Prevention by controlling risk factors
Sometimes measures to lower pressure in the eye, including eyedrops, eye massage, or removing fluid from the eye with a needle
Sometimes laser treatment of abnormal or bleeding blood vessels
For giant cell arteritis, corticosteroids
Because treatments tend not to be effective, preventing such blockages by controlling risk factors (for example, high blood pressure, diabetes, and other risk factors for atherosclerosis) is desirable.
When blockage of a central retinal artery does occur, immediate treatment is often given in an attempt to unblock the retinal artery. However, treatments are rarely effective. Pressure inside the eye sometimes can be lowered by giving drugs that lower blood pressure (such as timolol eye drops or acetazolamide taken by mouth).
Lowering the pressure inside the eye by massage or by anterior chamber paracentesis may dislodge a blood clot or embolus and allow it to enter a smaller branch of the vessel, thereby reducing the area of damage to the retina.
People with suspected giant cell arteritis are given high-dose corticosteroids either by mouth or by vein as soon as possible.
Laser treatment may be used to destroy abnormal blood vessels to treat or prevent neovascular glaucoma, prevent further vision loss from bleeding within the eye, or both. However, treatment of neovascular glaucoma is difficult.
Because people with central artery occlusion have an increased risk of stroke, doctors immediately refer them to a specialized stroke center for further evaluation.
More Information
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Eye Institute: A resource for learning about eye health (in English and Spanish) for adults and children, as well as access to outreach campaigns.
