DESCRIPTION: Literally, "half vision;" a condition resulting from malfunction or damage to one side of the optic tract (see diagram below). Images from only one half of each eye reach the brain; thus, there is only reception of half-fields for each eye.
TREATMENT: There is no treatment for hemianopia itself; the cause (e.g., tumor or hemorrhage) should be investigated and treated if possible. Visual fields losses can sometimes be alleviated with prism lenses, but their efficient use depends on the individual user (motivation, perceptual ability, etc.). Orientation and Mobility adjustments may be indicated. Reading may be affected, depending on whether the loss is in the right (in reading, the "anticipatory" field) or left fields.
IMPLICATIONS: Examination of the diagram will suggest that different types of visual losses occur when sites of malfunction differ (e.g., a tumor affecting the optic chiasm will cause visual impairment in both eyes, but a tumor affecting either optic nerve will affect only one eye).