NCIt definition : The round, central aperture of the eye, surrounded by the iris, through which light
enters.;
Alternative definition : CDISC: The round opening in the center of the iris in the eye.; NCI-GLOSS: The round opening in the center of the iris (the colored tissue that makes
the eye color at the front of the eye). The pupil changes size to let light into the
eye. It gets smaller in bright light and larger as the amount of light decreases.;