Hemianopsia is a partial blindness affecting half of the visual field in one or both eyes, caused by damage to the brain’s nerve pathways, stroke, or brain tumors. There are two variants of the disorder, and treatment may include rehabilitation training or specially designed glasses.
Hemianopsia is a vision defect in which half of the eye’s visual field is affected by blindness or reduced vision. One or both eyes may be affected by this partial blindness. The condition is usually caused by damage to the nerve pathways in the brain that control vision. The damage to the optical path that causes this type of visual impairment can be caused by physical damage to the brain, stroke, or brain tumors.
In optometry, the visual field of each eye is considered to have two halves, the temporal half and the nasal half. When considering the visual field of the eye divided vertically into two halves, the temporal half of the visual field is the outer half. The nasal half of the visual field is the internal half.
Where both eyes are affected, there are two main variants of hemianopic disorders. In the homonymous variant of this disorder, the patient’s vision is affected in the opposite half of each eye, whereby the nasal half is affected in one eye and the temporal half in the other. In the heteronymous variant, vision is impaired in both the nasal sides of both eyes, known as binasal hemianopia, and the temporal sides of both eyes, which is termed bitemporal hemianopia.
Causes of hemianopsia are usually severe brain problems such as strokes caused by bleeding in the brain, damage to the optic pathways, or brain tumors that press against the optic nerves. There are other, less serious causes, however, and these may only result in temporary vision loss. Some migraine sufferers can endure temporary attacks of hemianopsia, either during a migraine episode or immediately before a migraine. It can also occur temporarily in some patients who experience a transient episode of very high blood pressure, as can occur in eclampsia, a pregnancy complication.
Depending on the root cause, hemianopsia may remit spontaneously, as sometimes happens in stroke patients. However, if it persists for more than six months in such patients, it is likely to be a permanent condition. Treatment may include rehabilitation training to help sufferers adjust to their limited vision. If such training is successful, sufferers may even be able to drive. Sometimes, specially designed glasses are an effective way to improve the condition. These types of glasses may use prisms or mirrors to expand the wearer’s field of vision.
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