The Pupil: A Part of the Eye

The human eye is made up of many parts that work together to create vision. The pupil is an important part of the anatomy of the eye and is easily identified as the dark, black circle in the middle of the eye.

Significance

• The pupil is the opening in the center of the iris, or colored part of the eye. In the iris are two small muscles, called sphincters. One constricts or narrows the pupil in bright light while the other dilates the pupil in dim light, according to Eyes.com.

Size

• The diameter of the pupil can vary between 2 and 8 mm. According to Eyes.com, the opening determines the amount of light entering the eye. The pupil constricts to limit the amount of light entering the eye and dilates, or widens, in lower-light settings to maximize the amount of light. The pupils also change in relation to emotions, constricting when angry or suspicious and dilating when happy or surprised.

Function

• From the pupil, light then passes to the retina, or the light-sensitive area at the back of the eye. According to the Eye Doctor Guide website, the pupil acts in much the same way as the lens of a camera, widening to allow more light in, and constricting to prevent an excessive amount of light from getting in.