Pupillary response

Pupillary response or dilation of the pupil is a physiological response that varies the size of the pupil of the eye via the iris dilator muscle. It can have a variety of causes. It may be an involuntary reflex reaction to exposure to light. Or it may indicate interest in the subject of attention or indicate sexual stimulation. The pupils contract immediately before someone falls asleep.

A pupillary response can be intentionally conditioned as a Pavlovian response to some stimulus.

The latency of pupillary response (the speed at which it occurs) increases with age.

In ophthalmology intensive studies of pupillary response are conducted via videopupillometry.