Monday, April 6, 2009

Crystalline Lens

The crystalline lens is a transparent, biconvex structure in the eye. It focuses the image of an object on the retina. The transparent crystalline lens of the eye is located immediately behind the iris and is held in place by the zonule of Zinn ligaments. In order to switch its focus from a distant to a close object, or vice versa, the eye lens shape is changed by the contraction of the ciliary muscle which is connected to the zonule of Zinn ligaments. This adjustment of the lens is known as accommodation, which is similar to the focusing of a photographic camera via movement of its lenses.

The crystalline lens is composed of 4 layers of tissue, from the surface to the center: 1) capsule; 2) subcapsular epithelium; 3) cortex; 4) nucleus. The lens capsule is a smooth, transparent basement membrane that completely surrounds the lens. The lens epithelium is a simple cuboidal epithelium.