Corneal Refractive Therapy is the use of rigid gas-permeable contact lenses, normally worn only at night, to improve vision through the reshaping of the cornea. This method can be used as an alternative to eyeglasses, refractive surgery, or for those who prefer not to wear contact lenses during the day. The latter may be due to discomfort from working in air-conditioned or dusty environments, from extended computer usage which reduces blink rates and tear film production or from displacement or loss during sports activities.