Pupil

Definition

The pupil is the circular opening in the center of the iris of the eye that regulates the amount of light entering the eye. It appears black because most of the light entering it is absorbed by tissues inside the eye.

Related terms

Iris: The colored part of the eye surrounding the pupil that controls its size and amount of light reaching the retina.

Retina: A layer at the back of the eyeball containing cells sensitive to light that trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.

Optic Nerve: The nerve that transmits visual information from the retina to the brain