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Myopia control and even reversal are possible with the use of overnight orthokeratology lenses.
Baltimore-Myopia control and even reversal are possible with the use of overnight orthokeratology lenses, said Richard H. Schoen, OD, here at the annual Evidence Based Care in Myopia Control, Retina and Vision Enhancement meeting of The Wilmer Eye Institute, held in conjunction with the Maryland Optometric Association.
Proper fitting and lens maintenance are of paramount importance to achieving the best possible results.
"Overnight orthokeratology is relatively safe and reliably effective in situations of careful patient selection and appropriate oversight by the contact lens fitter and eye care practitioner," said Dr. Schoen, who is a clinical associate at the Wilmer Eye Institute, The Johns Hopkins School of Medicine, Baltimore.
In June 2002, the FDA granted overnight wear approval to a type of corneal reshaping called Corneal Refractive Therapy (CRT). New manufacturing methods and lens designs made it possible to achieve better results with orthokeratology lenses than in the past.
Several lens designs have FDA approval for overnight corneal reshaping, including CRT with Paragon CRT (Paragon Vision Sciences), Vision Shaping Treatment (VST, Bausch + Lomb), and designs from Blanchard Contact Lenses Inc., C&E G.P. Specialists, and Euclid Systems.
For patients who are surgery-averse and not necessarily interested in a permanent effect, orthokeratology can be an attractive option for spectacle independence.
"Even for those of us who don't intend to do Ortho-K, this is a very exciting area-the idea of myopia control and reversal," Dr. Schoen said.
Disadvantages of Ortho-K
There are some risks to using orthokeratology lenses, Dr. Schoen cautioned. These include failure to achieve results, ulcerative and infectious keratitis associated with overnight wear of rigid gas permeable (RGP) lenses, and unintended corneal toricity secondary to lens decentration.
"Within 20 or 30 minutes of placing these lenses in the eyes, you can see if they are effective. Some people just seem to have tough corneas [that] won't accept the molding affect. In others, it will mold right away," Dr. Schoen said. He cautioned, however, that sleeping positions might affect fit in some patients.
"We have to remember that people use these in the supine or prone position, while they are asleep. Sometimes we can put a lens on in the office, and it seems to fit, but the patient comes back for follow-up and there is unintended astigmatism," Dr. Schoen said.
Not everyone sleeps the same way. Some sleep on their backs, some on their stomachs, and some change throughout the night. Some clinicians actually fit the lenses in the office, leave the patient reclined in the exam chair, and come back to check the centration, he explained.
"Theoretically, then, this can be a pretty cornea-friendly technique," he said.
There has been some concern about microorganisms adhering to the lenses, "but with good patient compliance, the lenses can be kept clean, keeping the risk of infectious keratitis to a minimum," Dr. Schoen said.
"You really have to get centration with these lenses. If they don't center, you can create new astigmatism in these corneas, and then you have to go through a wash-out and do a better fit," Dr. Schoen said.
Compliance and follow-up
There has been sparse negative reporting on these lenses, as shown on the FDA's Manufacturer and User Facility Device Experience (MAUDE database, http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/search.CFM). According to Dr. Schoen, who has checked this Web site for reports on Ortho-K lenses, there have only been 15 reports on file from January 2001 through April 14, 2010.
"Most of them seem to indicate issues with bad compliance," he noted.
With Ortho-K lenses, there should be an emphasis on patient compliance and routine follow-up.
"Patients must be seen two to four times per year, because these lenses can degrade," Dr. Schoen said. "They can wear down, they can warp, and they can become rough. If they do so, the [patients lose] the Ortho-K effect. They don't get the applanation and the vision correction, and their corneal epithelium can be damaged.
"But it's also been found that even in ordinary use of RGP [lenses], you will have some breakdown of the pristine surface within about 1.5 months," he said, adding that some evidence suggests that after 50 days, RGP lenses develop surface roughness that may be clinically significant.
"Ortho-K lenses are high-quality lenses, but they have to be maintained properly. With modern lathing, they can be accurate to ±0.005 mm. So if you're getting a good fit, good centration, and the lens is in pristine shape, there is no reason the patient should not get a good outcome," Dr. Schoen said in conclusion.