Overnight Orthokeratology (OK) is an effective, temporary alternative to LASIK for the treatment of nearsighted patients, according to a new study published in the March issue of Optometry and Vision Science.
The study, Posterior Corneal Shape Changes in Myopic Overnight Orthokeratology, was performed by Professor Helen Swarbick, of University of New South Wales and Professor Jeong Ho Yoon from the University of Choonhae Health Science in Korea.
Orthokeratology is a clinical technique to reduce myopia using specially designed rigid contact lenses to manipulate the shape of the cornea.
The technique requires patients to wear the rigid lenses overnight for about six hours, to temporarily correct low to moderate myopia. Until now, it has been unclear exactly how OK works – whether the lenses reshape the front surface of the cornea alone, or bend and flatten the entire cornea.
OK lenses caused only a small and temporary change in the shape of the posterior (rear) cornea, and only slight thinning of the central cornea
For the study, 18 young adults with relatively mild myopia wore OK lenses overnight for 14 days and the researchers made detailed measurements of corneal shape and thickness before, during, and after treatment.
The researchers found that the changes were significant after the first night wearing OK lenses and that after 14 days, the myopia was almost completely eliminated. As a result, the participants had near-normal uncorrected visual acuity.
According to the study, these changes were linked to significant flattening of the anterior (front) portion of the cornea – and much of the change in corneal shape occurred after the first night wearing OK lenses. Although corneal flattening continued throughout the 14-day treatment period, about 80 per cent of the change occurred in the first four days.
In contrast, OK lenses caused only a small and temporary change in the shape of the posterior (rear) cornea, and only slight thinning of the central corneaStudy says OK is an
OK Treatment for Myopia.
Drs. Yoon and Swarbick said their research results “support the current hypothesis that the OK refractive effect is achieved primarily through remodeling of the anterior corneal layers, without overall corneal bending”.