Ortho-K uses gas permeable contact lenses to correct or minimize the refractive error of the Human Eye. Flattening the cornea reduces the focusing power of the eye. Since the amount of corneal flattening can be accurately controlled, it is possible to bring the eye into correct focus and compensate for the refractive error.. After the contact lens is removed, the cornea retains its flattened shape for part or all of the remainder of the day. A retainer lens must be used each night or atleast, most nights, to maintain the corneal flattening, or the myopia will revert to the pre-treatment level. Ortho-K is also used to decrease farsighted ness by steepening the central cornea.
The Cornea makes up about two-thirds of the eye's total power to focus the light precisely on the retina (receiving screen) which is located in the back of the eye. By slight modifications in the shape of the cornea, clear functional vision may be restored for a period of time.
This improvement is temporary, therefore lens wear must be continued on a prescribed wearing schedule to maintain the therapeutic effect of the myopia reduction. This flattening is accomplished by shifting the outer layer of the central cornea - the epithelium - more peripherally, thus flattening it. The amount of flattening or shift is approximately 6 microns per diopter of myopia. A micron is one millionth of a meter a human hair is about 125 microns.There may also be some bending of corneal tissue to achieve flattening. This would be similar to pressing gently on a balloon producing a depressed surface.
Thus after a night of wearing the Ortho-K lens, One may not need any glasses or other devices for the following day. Unlike PRK or LASIK, Ortho-K is reversible.