night vision [AS, niht, night; L, visio, seeing] , a capacity to see dimly lit objects. It stems from a chemophysical phenomenon associated with the retinal rods. The rods contain the highly light-sensitive chemical rhodopsin, or visual purple, which is essential for the conduction of optic impulses in subdued light. Night vision is sharpest at the periphery of the retina because of the concentration of rods. Night vision may be diminished by a deficiency of vitamin A, an important component of rhodopsin.
