Lens

The lens is a transparent, biconvex, elastic structure which focuses light onto the retina. It lies between the iris and the vitreous body, suspended at the center of the ciliary body by the ciliary zonule, which attaches to its equator. By deforming under the action of the ciliary muscles, the lens participates in visual accommodation.

The anterior surface of the lens is in contact with the aqueous humor of the posterior chamber and the pupillary margin of the iris. Its posterior surface faces the hyaloid fossa, in contact with the vitreous body. In most domestic species, with the exception of the cat, the posterior surface is more convex. The axis lentis is aligned with the optic axis.

The lens is composed of a transparent epithelial substance, neither vascularized nor innervated, surrounded by the capsule of lens. The lens substance is composed of lens fibers that join the anterior and posterior poles of the lens, forming concentric lamellae. This arrangement forms the Y- or X-shaped radii lentis on both sides of the lens, corresponding to the points where the fibers are anchored. These fibers are derived from cells of the lens epithelium, present only on the anterior surface of the lens. The lens substance is divided into two parts, the cortex of lens and nucleus of lens.