Crystalline Lens

Definition

The lens is a transparent biconvex structure inside the eye with the primary function of focusing light on the retina and changing the focus of the eye.

Anatomy

The lens consists of the lens capsule, the epithelium, cortex, and nucleus. It is held in its position between the iris and the vitreous cavity by the zonular fibers and has the ability to refract light because its refractive index (about 1.4 in the center and 1.36 in the periphery) is different from that of the aqueous humor and the vitreous (1.336) (Atchison and Smith 2002).

The lens capsule is a membrane enveloping the lens with a thickness between 5 and 25 μm consisting of collagen type IV. The anterior capsule is thickest in the midperiphery and thinnest at the anterior pole of the lens. The capsule on the posterior surface is likewise thinnest in the area of the posterior pole and thickens towards the periphery. Under the anterior capsule of the lens and at the lens equator the monolayered lens epithelium is...