lenses worn directly against the eye, separated from it only by a film of tear fluid. Corneal microlenses cover only the cornea, while haptic lenses cover some of the surrounding sclera as well. Contact lenses are used mainly in place of glasses to correct long- and short-sightedness and other errors of refraction, but bandage contact lenses may be used in a protective capacity to relieve the pain of a damaged cornea or as part of the treatment of some types of corneal disease. Contact lenses may be made of hard or soft materials, which have very different properties. Hard Perspex lenses have been partly replaced by gas-permeable lenses, which allow oxygen to pass from the atmosphere to the cornea.
Medical dictionary. 2011.