lens
1. The nearly spherical body in the eye, located behind the cornea, that focuses light rays onto the retina.
2. A device used to focus light into the eye in order to magnify or minify images, or otherwise correct visual problems. Eyeglass lenses, contact lenses, and intraocular lenses are examples. Sometimes a lens provides only a cosmetic benefit, as in non-correcting color contacts, special effect contacts, or contacts that hide a disfigurement of the eye. Other times a lens protects the eye, as in safety glasses or sunglasses. A bandage contact lens may be applied after eye surgery. And contact lenses used in ortho-k or corneal refractive therapy are designed to reshape the cornea for better vision when the lens is removed.