So in a society that reads from left to right, left hemianopia has little effect on reading ability, but right hemianopia can be devastating.

Hemianopia, or half-blindness, arising from these pathological changes, is of very varying degrees of severity, according to the nature and extent of the particular lesion.

Destruction of the calcarine region of one hemisphere produces therefore “crossed hemianopia,” that is, loss of the opposite half of the field of vision.