Orthokeratology (ortho-k) is a non-surgical treatment using specially designed high oxygen permeable retainer lenses to gently reshape the cornea (the front surface of your eye); these special retainers are worn only while you sleep and provide clear, natural vision when the retainers are removed upon waking. The principle is similar to a dental retainer used by an orthodontist to straighten misaligned teeth. The vision retainers are similar to contact lenses and are only worn while you sleep. This method can be used to treat myopia (nearsightedness) and astigmatism as an alternative to eyeglasses, refractive surgery, or daytime contact lenses.
Ortho-k may sometimes be referred to as corneal refractive therapy (CRT), overnight vision correction, Gentle Vision Shaping System, or Vision Shaping Technology.