A person’s pupils may be of different sizes (anisocoria) for several reasons, including physical trauma, response to light, and infection. The condition may also be present from birth.

A study participant with the device used to record pupil movements during sleep. © Neural Control of Movement Lab / ETH Zurich Though sleep is a time to power down ...

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 ...