Orthokeratology is a form of reversible, refractive correction involving the overnight use of gas-permeable contact lenses to reshape the contour of the cornea while you sleep. These oxygen-intense, “breathable” lenses work to temporarily reverse the effects of Myopia during the night so the wearer can experience clear vision the following day—without the use of glasses or contacts. Ortho-k is used primarily to slow the progression of mild Myopia in adults and children, although it can aid in the temporary correction of low-degree astigmatism, hyperopia, and presbyopia as well.