"Miosis" is a medical term that describes the constriction of the pupils. Learn its causes, symptoms, and how to treat it.

Eye color depends on the iris ... action when it squeezes or relaxes to let in more or less light through the pupil. The iris ...

They also tend to have pupils that open more widely in low light ... (Interestingly, different animals have different color tapeta, a fact that can aid in nighttime animal identification.) ...