loss of one of the halves of the visual field in both eyes, the cause of which is a disease of the optic pathways of the central end of the optic nerve (behind the chiasm). With hemianopsia, there is a pronounced pathology of visual perception. If the left half of the visual pathways is affected, a person is deprived of the ability to observe the right half of the visual field. With a disease of the visual pathways on the right side, a person is unable to see the left half of the visual field. Hemianopia is usually accompanied by impaired spatial vision.