Orthokeratology, or "ortho-K," is a non-surgical technique for temporarily reducing myopia using rigid gas permeable ("RGP" or "GP") contact lenses. The treatment consists of wearing specially-designed GP lenses for a small part of the day (or night) that flatten the curvature of the central cornea, thereby reducing nearsightedness. After wearing the GP lenses for a specified period of time (usually overnight), most patients can then remove the lenses and see clearly without eyeglasses or contact lenses for the remainder of the day (or longer).
Ortho-K is proven effective for the temporary correction of up to -4.00 diopters (D) of myopia. During the treatment, a series of GP lenses are worn over the course of a few weeks to progressively bear down on the center of the cornea, changing its shape to clearly focus light. Unfortunately, because of the natural resilience of the cornea, the original corneal shape will start returning to its normal shape relatively soon after the GP lens is removed. Consequently, ortho-K patients must periodically wear a "retainer" lens to re-establish the desired corneal shape.
Ortho-K patients may experience fluctuating vision during the day and may need many follow-up office visits. First-time rigid gas permeable contact lens wearers may have difficulty getting used to wearing them. For these reasons, orthokeratology may not be a good value for many patients, compared to eyeglasses, regular contact lenses, or refractive surgery. But ortho-K may be a valuable option for someone who desires LASIK laser vision correction but is not old enough for refractive surgery. This procedure may also be appropriate for people who want to be able to see without glasses or contact lenses, but are not willing to accept the risks associated with refractive surgery.