What is "hemianopsia"

n. (context medicine English) blindness in one half of the field of vision of either or both eyes.

n. blindness in one half of the visual field of one or both eyes [syn: hemianopia]

Hemianopsia, or hemianopia, is a decreased vision or blindness ( anopsia) in half the visual field, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma.

This article deals only with 'permanent' hemianopia and not with transitory/temporary hemianopia as identified by William Wollaston PRS in 1824 (Ganzzaniga, Ivry and Mangun, Cognitive neuroscience: the biology of the mind, W W Norton and Company, New York and London, p 9).