The authors have studied a response of the cornea (a change in its thickness, shape, refraction, and endothelium) to nocturnal orthokeratotology - a procedure for temporarily diminishing or removing myopic refraction, which is accomplished by wearing rigid gas-permeability contact lenses that change corneal shape and optical strength. The orthokeratological technique has been ascertained to be an effective modality for the temporary reversible reduction of mild and moderate myopic refraction. In some cases, the refractive effect of the technique may run up to 7.5 diopters. The mechanism of action of orthokeratological contact lenses is to form an epithelial diverging biolens onto the corneal surface by transferring epithelial cells from the center to the paracentral parts. Wearing of orthokeratological contact lenses does not cause clinically significant symptoms of damages to the epithelium and corneal stroma or lead to altered endothelial cell density.