Definition: The hole or opening that is located in the center of the iris of the eye. The pupil controls the amount of light that enters the eye. Pupil size is controlled by the dilator and sphincter muscles of the iris.
Pupil
By Troy Bedinghaus, O.D., About.com Guide
Updated July 25, 2008
About.com Health's Disease and Condition content is reviewed by the Medical Review Board
Pupil
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