During sleep, do pupils become more miotic or mydriatic?

During sleep, pupils typically become more miotic, meaning they constrict in size. This phenomenon is primarily influenced by the activity of the parasympathetic nervous system, which is more active during sleep. The resting state of the body, alongside reduced visual inputs while the eyes are closed, leads to a generalized response that favors constriction of the pupils.

Miosis during sleep helps facilitate a more relaxed and restorative state. Additionally, the absence of light exposure while a person sleeps diminishes stimulation of the sympathetic nervous system, which would normally lead to pupil dilation.

It's important to note that while some variability in pupil size can exist among individuals due to factors like lighting conditions, ocular health, and specific sleep stages (such as REM sleep), the overall trend across the majority of people is towards miotic pupils during sleep. This is a well-established physiological response, emphasizing the control the autonomic nervous system exerts on pupil size with changes in state, such as transitioning from wakefulness to sleep.