The Lens (vision) reference article from the English Wikipedia on 24-Apr-2004
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Lens (vision)

Image:Focus in an eye.png
Light from a distant object and light from a near object being brought to a focus by changing the curvature of the lens.
The lens is a component of the eye. It refracts light entering the eye and projects it onto the retina.

The lens is clear and flexible; its curvature is controlled by muscles. By changing the curvature of the lens, the eye can focus at different "depths of field".

See also: visual perception, eye, iris, lens (optics)