Orthokeratology is the science of modifying the curvature/shape of the cornea to change how light is focused on the retina (back part of the eye). The cornea is a clear, dome shaped structure that overlies the colored iris. Corneal tissue is clear, and it closely resembles a wet skin, and like skin tissue, it is very pliable. The cornea functions as a protective layer that separates the eyes contents from the environment and its unique structural curvature is able to bend the light rays towards the back of the eye. It is responsible for most of the eyes corrective power and contributes to various conditions such as nearsightedness (myopia), farsightedness (hyperopia) and astigmatism.