A reflex in which light shone into one eye causes the pupils of both eyes to constrict involuntarily, protecting against damage to the retina and causing a temporary threshold shift (TTS), similar to the acoustic reflex in response to loud noise. The reflex is found even in people whose primary visual cortex is destroyed, rendering them totally blind. Optic nerve damage results in equal pupils, neither responding to light shone into the eye on the damaged side but both responding normally to light shone into the other eye, whereas oculomotor nerve damage results in a dilated pupil on the damaged side that does not respond to light shone into either eye. Also called the consensual pupillary reflex, the consensual light reflex, Haab's pupillary reflex, the light reflex, or the pupillary reflex. See also reflex.