Controls how much light enters the pupil. Pupil Hole in the middle of the iris. Allows light to pass through as it enters the eye. Lens Transparent, bi-convex, flexible disc behind the iris.

Pupillometry measures the size and reactivity of the pupil, the dark circle at the eye’s centre through which light enters. Typically, the pupil contracts and dilates depending on the amount of ...

Researchers were able observe eye movements during sleep over a course of several hours for the first time. Pupil size also fluctuates constantly during sleep, and is linked to the level of brain ...