Orthokeratology is a relatively new field of optometry concerned with reshaping the cornea to fix myopia, or nearsightedness. Wearing an individually designed set of contact lens during sleep, patients who qualify to undergo what is known as corneal refractive therapy (CRT) often have their sight repaired enough at night that they do not need to wear glasses or contact lenses during the day. This nonsurgical treatment requires nighttime vigilance, since nearsightedness will return within just a few days if the lenses are not worn nightly.
Corneal refractive therapy is meant to be a temporary correction for myopia requiring a fairly strict regimen of use and new lenses about once a year. This is to make computerized adjustments to the lenses, which are designed to reshape the cornea at night to allow the retina to better refract and focus light during the day. Anyone who is nearsighted, even at a high level of -6.00 diopters or less, can qualify as long as he or she does not have an astigmatism that registers higher than -1.65 or -1.75 diopters, depending on the lenses being used.
The U.S. Food and Drug Administration granted its first approval to corneal refractive therapy in 2002, with about 93 percent of patients studied reaching at least 20/32 vision, and 67 percent achieving 20/20. A corrective lens made by Paragon Vision Science was the first on the market, offering a breathable material and computerized calibration for fine-tuned lens production. As of 2011, just two brands — Paragon CRT® and Bausch & Lomb's Vision Shaping Treatment® — dominate the market. Each company trains and certifies optometrists to create lenses and administer this treatment to adults and even children.
Manufacturers of corneal refractive therapy lenses tout improvements in patients' myopia within a few days of beginning treatment. They state that clear vision is typically achieved within about two weeks. During the treatment, old prescriptions are not likely to be adequate. Some might have soft contacts prescribed that provide corrective assistance. Doctors might advise patients to continue wearing the lenses during some daytime hours until full, focused sight is restored. Lens wearers can always see through CRT lenses — even if awakened at night.
Farsightedness, or hyperopia, still is not fully correctable with corneal refractive therapy, as of 2011. Presbyopia sufferers, however, who regularly need the assistance of bifocals, can benefit from the technology. According to Paragon, optometrists can place the eyes in "monovision mode," with one eye corrected for near and the other at a distance.