Contact lens is a device used to correct vision. Contact lenses are most commonly used to correct myopia (nearsightedness) and hyperopia (farsightedness). The lenses can be made of hard or soft plastic. They float on a thin layer of tears on the surface of the cornea (clear front surface of the eyeball). Contact lenses are curved to focus light rays on the retina. When the light rays are properly focused, a person sees clear images of normal size. Contact lenses provide more natural vision than glasses because they also allow normal side vision.