Disruptions of Blood Supply

The eye is extremely sensitive to any disruption of its blood supply. Disruptions are relatively uncommon but occur more frequently as people get older. Most disruptions of blood supply result at least partly from atherosclerosis, in which cholesterol and fatty material in the blood form deposits (plaques) in the arteries. Less common conditions that disrupt blood flow to the eye include inflammation of the blood vessels (vasculitis, such as temporal arteritis), infection in or around the eye, damage from radiation, and injury to the eye.

When blood flow to the eye is disrupted, the person experiences vision loss, usually in one eye. Vision may disappear completely or in patches. Sometimes vision is lost suddenly and is regained within a few minutes (a phenomenon called amaurosis fugax). This kind of sudden, temporary vision loss requires immediate medical attention, because it may indicate an impending stroke or permanent blindness.

Diagnosis and treatment of vision loss due to impaired blood flow to the eye depend on the cause.

Retinal Vein Blockage

Retinal vein blockage is blockage of a vein that drains blood from the eye.

The blockage can affect the largest vein in the eye (central vein) or a much smaller branch. Retinal vein blockage is the most common cause of blood supply disruption to the eye in older people. It occurs more commonly in people with atherosclerosis and glaucoma. People with leukemia or lymphoma, autoimmune disease, or abnormalities of the blood that cause excessive clotting may also develop retinal vein blockage.

An eye doctor diagnoses retinal vein blockage by examining the back of the eye and by taking pictures of the eye's blood supply (a test called fluorescein angiography). No treatment has been proven effective for the blockage itself. However, complications of retinal vein blockage, including swelling of the macula, bleeding into the eye, and glaucoma caused by growth of abnormal blood vessels on the iris, can often be prevented or treated with laser therapy.

Retinal Artery Blockage

Retinal artery blockage is blockage of an artery that supplies blood to the retina.

The blockage can affect the largest artery supplying the retina (central artery) or a much smaller branch. The central artery or its branches most often become blocked because of atherosclerosis or an embolus (a piece from a larger blood clot in some other part of the body that has broken off and traveled through the bloodstream). Less often, people with temporal arteritis, inflammation of the optic nerve, infection around the eye, and clotting disorders develop a blockage. Rarely, increased eye pressure in a person with glaucoma can become high enough to cause blockage of the retinal artery.

An eye doctor diagnoses retinal artery blockage by examining the back of the eye and by performing tests to observe blood flow in the vessels (fluorescein angiography [in which a dye is injected into an arm vein and the retina is photographed] or Doppler ultrasound scanning).

No treatment has been proven effective for retinal artery blockage due to atherosclerosis. However, some doctors try improving oxygen delivery to the tissues by massaging the eyeball, by withdrawing fluid from the eye to lower pressure on the blood vessels, and by promoting dilation of the blood vessels, sometimes by having people breathe a limited amount of carbon dioxide.

If begun early, treatment can be effective for less common causes of retinal artery blockage. Treatment options include corticosteroids for inflammation of the artery or optic nerve; antiviral or antifungal drugs for infection; and anticoagulants for clotting disorders. Anyone without one of these less common causes should be tested for carotid artery disease and treated for any risk factors for atherosclerosis.

Retinal Emboli

Emboli are blood clots or clumps of cholesterol and fatty material that break off from atherosclerotic plaques.

When emboli lodge in blood vessels in or close to the eye, the eye's blood supply can be suddenly blocked. Emboli most often come from arteries in the chest or neck, but they can also come from the heart.

Emboli are a common cause of sudden but temporary vision loss; they can also cause permanent vision loss. Vision loss from emboli is sometimes described as a slow dimming of light or as a window shade being pulled down or up over the eye. When emboli travel to the brain and the eye at the same time, vision loss may be accompanied by loss of speech or weakness in an arm and leg. If these symptoms last more than a day, they indicate that the person has had a stroke.

A doctor diagnoses the source of retinal emboli using ultrasonography or magnetic resonance angiography. Echocardiography and recordings of heart rhythm may be performed to determine if the person is at risk for further emboli.

Treatment may involve surgery (carotid endarterectomy) if test results show that the emboli may have come from the arteries in the neck and if the arteries are significantly narrowed. Otherwise, aspirin or other anticoagulants (sometimes called blood thinners) are used. Warfarin is given if test results show that emboli may have come from the heart. Treatment of atherosclerosis is important as well.

Ischemic Optic Neuropathy

Ischemic optic neuropathy is a sudden painless loss of vision in one eye from insufficient blood flow to the optic nerve.

The cause is unknown. Atherosclerosis, diabetes, and high blood pressure may increase the risk of developing ischemic optic neuropathy. Temporal arteritis is a treatable form of ischemic optic neuropathy.

Some people have pain or discomfort around the eye. An eye doctor diagnoses the condition by examining the eye. No proven treatments are available for most forms of ischemic optic neuropathy. For some people, vision improves without treatment. Only a small percentage of people experience the same symptoms in the other eye. Control of risk factors for atherosclerosis may help prevent ischemic optic neuropathy.

People with optic neuropathy due to temporal arteritis experience vision loss, which may be sudden in one eye. They may also experience headache, scalp tenderness at the temple, fever, and jaw pain when chewing. A doctor diagnoses the condition by examining the eye, performing blood tests, and performing a biopsy of the temporal artery. Treatment involves use of corticosteroids, mainly to prevent occurrence of disease in the other eye, but also to reduce risk of further vision loss in the affected eye.

Occipital Lobe Stroke

An occipital lobe stroke involves loss of blood flow to the part of the brain that receives images from the eye.

Causes are the same as those for other strokes. Partial vision loss occurs in both eyes and involves the same area of vision. For example, both eyes can see to the right side but lose vision on the left side. Generally, 50% or less of the area of vision is impaired. Diagnosis and treatment are the same as for other types of stroke.