The March 2013 issue of Optometry and Vision Science features an article titled Posterior Corneal Shape Changes in Myopic Overnight Orthokeratology. The study was conducted by Jeong Ho Yoon, PhD, of the University of Choohae Health Science, and Helen A. Swarbick, PhD, FAAO, of University of South Wales, Sydney, Australia. In this study, OK lenses flattened the front of the cornea. According to Anthony Adams, OD, PhD, and Editor-in-Chief of Optometry and Vision Science, the only part of the cornea that is affected by OK lens treatments is the very front surface layers.
HOW ORTHOKERATOLOGY WORKS
Orthokeratology is a clinical technique used to reduce nearsightedness, also commonly called myopia. By using specially made, rigid contact lens, eye doctors can manipulate the shape of the cornea. Dr. Anthony Adams explains that the cornea is the transparent front part of the eye, which is responsible for letting light into the eye. To explain how OK works, Dr. Adams says to liken the process to the way an orthodontist changes the alignment of teeth with braces. This same realigning method is applicable to OK treatments as well.
RECOMMENDED OK TREATMENT COURSES
As of now, the recommended treatment for OK lens wearers is to wear the lenses overnight for at least six hours. However, while eye doctors recognized that OK was working for the temporary correction of myopia, they weren’t sure exactly why it was helping. To determine whether the contact lenses were reshaping just the front surface of the cornea, or if the lenses were bending and flattening the entire cornea, Dr. Yoon and Dr. Swarbick set up a two week study using 18 young adults participants.
OK STUDY PARTICIPANTS
Each participant in the study had relatively mild myopia. The study followed each participant for 14 days. During this time, the participants wore the OK lenses overnight for two weeks. With the help of sophisticated equipment, each participant had detailed measurements of their corneal taken before the study began, during the study, and immediately after the study was complete.
OK STUDY RESULTS
As previous studies had already proven, participants in the OK study had significant reduction in their myopia, which improved their vision. In fact, most of the participants noticed dramatic differences after just one night of wearing the contact lenses. By the end of the 14th night, many participants had no physical symptoms of myopia. Instead, participants had nearly normal visual acuity without the help of any corrective lenses or eyewear.
CHANGES TO THE ANTERIOR PART OF THE CORNEA
After examining the data, Dr. Yoon and Dr. Swarbick were able to determine that the study participants achieved better vision through the flattening of the front, also known as anterior, portion of their corneas. In fact, the changes in the corneal shape were dramatically noticeable after the first night of the study, which is why study participants noticed results almost immediately. The corneal flattening process continued throughout the 14 day study, however, the majority of the corneal flattening, about 80%, occurred during wearer’s first four days of treatment.
CHANGES TO THE POSTERIOR PORTION OF THE CORNEA
During the study, Dr. Yoon and Dr. Swarbick determined that only temporary and small changes occurred in the posterior portion of the cornea. In the central cornea, there was only slight thinning that occurred.
FINAL RESULTS OF THE OK STUDY
With all the data analyzed, Dr. Yoon and Dr. Swarbick were able to prove that their hypothesis, which was that OK treatments worked by remodeling the anterior section of the cornea without overall bending of the cornea, was correct.
As a result of this finding, it can be concluded that OK contact lenses are an effective treatment for patients with mild myopia. To work properly, patients must be fitted with customized, rigid contact lenses that are designed with the desired cornea changes in mind.
IS OK TREATMENT AN ALTERNATIVE TO LASIK?
OK lens treatment is an alternative to LASIK surgery for mild myopia, but there are significant differences in the two treatments. LASIK generally requires one treatment to correct myopia. With OK lens treatment, patients must continue to wear the special contacts on a regular basis to maintain their improved eyesight. If a patient discontinues wearing the OK lenses, their mild myopia will eventually return.
As a result of their study, Dr. Yoon and Dr. Swarbick hope that more patients with mild myopia will be able to find relief from their condition.
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