Contact lens

A contact lens (also known as a "contact") is a corrective, cosmetic, or sometimes protective lens located on the cornea of the eye.
Contact lenses are obtainable in a number of varieties, including hard and soft. Hard contacts are classically not disposable, while soft contacts often are. Some soft contacts are also well-known as extended wear lenses. Contact lenses (both soft and hard) are made a variety of types of polymers, the latest containing some variant of silicone hydrogel. Previously, hard contact lenses were made of a polymer known as PMMA. They have since been replaced by rigid gas-permeable (RGP) contact lenses. Many contact lenses are made of hydrophilic (water-absorbing) materials, thereby allowing oxygen to reach the cornea, and make the lens more comfortable to wear.
Heavily tinted contacts are tinted to change the color of the iris, and are used for cosmetic reasons. Some standard contact lenses are somewhat tinted in order to make them more visible for handling purposes.