Ischemic optic neuropathy is damage of the optic nerve caused by a blockage of its blood supply.
Blockage of the blood supply to the part of the optic nerve within the eye can lead to impaired function of optic nerve cells and vision loss. Two types can occur: nonarteritic and arteritic.
Nonarteritic ischemic optic neuropathy occurs more frequently and usually occurs in people about age 50 and older. Vision loss is not usually as severe as in arteritic ischemic optic neuropathy. Risk factors include high blood pressure, smoking, diabetes, and atherosclerosis. Other risk factors may include obstructive sleep apnea, use of certain drugs (for example, amiodarone and possibly phosphodiesterase-inhibiting drugs, such as sildenafil, which are used to treat erectile dysfunction), a tendency to develop blood clots, and low blood pressure at night.
Arteritic ischemic optic neuropathy usually occurs in people about age 70 and older. The blood supply to the optic nerve is blocked due to inflammation of the arteries (arteritis), most notably giant cell arteritis (see Giant Cell Arteritis).
Loss of vision may be rapid (over minutes, hours, or sometimes days) but is painless. Depending on the cause, vision may be impaired in one or both eyes. Vision in the involved eye or eyes can range from almost normal to complete blindness. A small area of vision loss at the center of the visual field slowly enlarges and can progress to complete blindness. People with giant cell arteritis tend to be older, and their loss of vision tends to be more severe. They may have pain when they chew, headaches, muscle aches and pains, and pain when they comb their hair.
Diagnosis involves examination of the back of the eyes with a light with magnifying lenses (ophthalmoscope). Determining the cause involves determining whether the person has any of the disorders known to be risk factors.
If giant cell arteritis is suspected as a cause, blood tests and removal and examination of a temporal artery tissue sample under a microscope (biopsy) may be done to confirm the diagnosis. Blood tests determine the erythrocyte sedimentation rate (ESR), the C-reactive protein level, and the levels of certain types of blood cells (complete blood count). Results of these tests may indicate inflammation that is characteristic of giant cell arteritis. If a person has no symptoms of giant cell arteritis, magnetic resonance imaging (MRI) or computed tomography (CT) of the brain may be done to make sure the optic nerve is not being compressed by a tumor.
Other tests may be necessary depending on what causes are likely. For example, if people have symptoms of obstructive sleep apnea (such as excessive daytime sleepiness or snoring), polysomnography (see Testing) may be done. If people have had blood clots, blood tests may be done to diagnose blood-clotting disorders.
About 40% of people with nonarteritic ischemic optic neuropathy spontaneously recover some useful vision. In this condition, repeat episodes in the same eye are extremely rare. Involvement of the other eye is estimated to occur in about 20% of affected people over the next 5 years.
There is no effective treatment for arteritic ischemic optic neuropathy, and most lost vision is not recovered. In people with arteritic ischemic optic neuropathy caused by giant cell arteritis, loss of vision in the other eye occurs in 25 to 50% of people within days to weeks (and more over time) if treatment is not started.
In people with nonarteritic ischemic optic neuropathy, treatment involves controlling blood pressure, diabetes, and other risk factors for atherosclerosis. Other causes, such as blood-clotting disorders and obstructive sleep apnea, may also require treatment.
In people with arteritic ischemic optic neuropathy caused by giant cell arteritis, high doses of corticosteroids are given by mouth and/or vein to prevent loss of vision in the other eye. The role of aspirin in preventing involvement of the other eye is being investigated, although at this time there is no evidence to support its use.
Magnifiers, large-print devices, and talking watches (low-vision aids) may help people with loss of vision.
Last full review/revision October 2014 by James Garrity, MD