A loss of vision in the corresponding halves of the visual fields in the two eyes. It is produced by lesions of the visual pathway behind the optic chiasm, but not by damage to the retina or optic nerve. See visual field defects.
Homonymous hemianopsia is a medical term for a type of partial blindness resulting in a loss of vision in the same visual field of both eyes. It is usually caused by injury to the brain itself such as stroke or trauma, rather than malfunctioning of the eye itself. Vascular and neoplastic (cancerous) lesions of the optic tract or visual cortex can cause a contralateral homonynous hemianopsia.