The lens is one of refractive structures in the eye - along with the cornea it is is responsible for focusing images onto the retina for conversion to nerve potentials as part of the visual process.  The lens is located in the eye behind the iris and pupil.  It comprises a thin outer capsule surrounding the more peripheral cortex which in turn surrounds the central lens nucleus.  A single layer of cells the lens epithelium) lies immediately beneath the anterior part of the capsule.  The lens epithelium extends into the equatorial region of the lens where it forms lens fibers.  The lens continues to grow throughout life gradually adding layers of lens fibers to the outer cortex.

    The lens diseases most commonly encountered in the horse are cataracts and lens luxation..