A contact lens is a corrective or cosmetic lens placed on the cornea of the eye atop the iris. The idea of applying a corrective lens directly to the surface of the eye was first proposed and sketched by René Descartes in 1636, but in was not until 1887 that the German physiologist Adolf Eugen Fick constructed the first successful contact lens.
Made of various kinds of plastic, contact lenses come in a number of varieties, including hard and soft (although soft is by far more common now), and disposable and extended-wear. The specific dioptre needed to treat the patient's condition
