Illustration copyright 2000 by Nucleus Communications, Inc. All rights reserved. http://www.nucleusinc.com

The lens is located behind the iris and is normally clear. Light passes through the pupil, the dark area in the center of the iris, to the lens. Small muscles attached to the lens can change its shape. Tightening or relaxing these muscles causes the lens to change shape, allowing the eyes to focus on near or far objects (accommodation).