March 5, 2013
Myopia-Curing Contact Lenses Alter Front Part Of The Cornea
redOrbit Staff & Wire Reports - Your Universe Online
Wearing a special type of contact lens overnight can improve the vision of nearsighted patients, and it does so only by changing the front portion of a person´s cornea — not the entire part of the eye that refracts light — researchers claim in a recently published study.
The technique is known as orthokeratology (OK), and according to Drs. Jeong Ho Yoon of South Korea´s University of Choonhae Health Science and Helen A. Swarbick of the University of New South Wales in Australia, it can provide rapid improvement for those suffering from myopia by using specially designed rigid contacts.
Those contacts manipulate the individual´s cornea, which accounts for two-thirds of an eye´s total optical power, resulting in improved vision. Their findings have been published in this month´s edition of Optometry and Vision Science, the official journal of the American Academy of Optometry.
"This study appears to show that it is only, or primarily, the very front surface layers of the cornea that are altered by OK contact lens treatment," Dr. Anthony Adams, the publication´s editor-in-chief, said Monday in a statement.
Adams went on to compare wearing the OK contacts to using braces to correct the alignment of one´s teeth, saying, “Wearing these lenses overnight for about six hours is currently the treatment approach for most clinicians who use OK for the temporary correction of low to moderate myopia.”
In order to find out exactly how OK reduces nearsightedness — that is, whether or not they bend and flatten the entire cornea, or just the front surface of it — Yoon and Swarbick recruited 18 young adults with relatively mild myopia. They had each participant wear the special contact lenses overnight for a total of 14 days, while taking detailed measurements of the subjects´ corneal shape and thickness before, during, and after the treatment.
After just one night wearing the OK lenses, the subjects experienced reduced myopia and improved vision, the researchers said. By the end of the two-week period, their nearsightedness had been nearly eliminated, leaving the volunteers with close to normal visual acuity, even without glasses. Those changes were linked to “significant flattening” of the front portion of the cornea, Yoon and Swarbick discovered.
"Overall, our results support the current hypothesis that the OK refractive effect is achieved primarily through remodeling of the anterior corneal layers, without overall corneal bending," the doctors said.
They added they were hopeful their findings "will provide a more complete picture of overall corneal changes during myopic OK,” including the fact wearing these special lenses does not alter the curvature of the rear part of a person´s cornea — at least, not within the first 14 days of use.