Ischemic Optic Neuropathy
Blockage can occur with inflammation of the arteries (called arteritic, typically as part of a disorder called giant cell arteritis) or without inflammation of the arteries (called nonarteritic).
The only constant symptom is painless vision loss, which may be sudden.
Doctors make the diagnosis by symptoms and by looking in the person’s eye with an ophthalmoscope.
Blood tests and sometimes biopsy of temporal artery tissue are done to diagnose giant cell arteritis.
Treatment for the nonarteritic variety is not effective.
Treatment for the arteritic type does not restore vision but can help protect the unaffected eye.
(See also Overview of Optic Nerve Disorders.)
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.
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.
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) and a visual field examination to measure central or peripheral vision loss. 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 may be done. If people have had blood clots, blood tests may be done to diagnose blood-clotting disorders.
There is no effective treatment for nonarteritic ischemic optic neuropathy. However, 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.
In the arteritic variety caused by giant cell arteritis, vision loss is typically greater than in nonarteritic ischemic optic neuropathy. Prompt treatment does not restore lost vision in the affected eye but protects the unaffected eye. Inadequate treatment increases the risk of vision loss in the other eye.
In people with nonarteritic ischemic optic neuropathy, treatment to restore vision loss is ineffective. Treatment involves reducing risk factors for atherosclerosis, including controlling blood pressure and diabetes. 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 as soon as possible to prevent loss of vision in the other eye. Adding tocilizumab (a drug that decreases inflammation) to corticosteroids has recently been shown to help people with giant cell arteritis.
Magnifiers, large-print devices, and talking watches (low-vision aids) may help people with loss of vision.