Blindness in half of the visual field of each eye, usually caused by stroke or head injury.

In homonymous hemianopsia, the same side (either left or right) of the visual field of each eye is affected. This can occur if there is an injury or lesion of the optic nerve on brain-side of the optic chiasm.

Binasal hemianopsia is a case of partial blindness in which the inner halves of each eye are affected. Bitemporal hemianopsia refers to the situation in which the outer half of the visual field is affected. These can be due to a lesion or injury in the region of the optic chiasm or by a pituitary tumor.