MONDAY, March 1, 2004 (HealthDayNews) -- Children who wore contact lenses overnight as part of a nearsightedness treatment called orthokeratology developed corneal ulcers and suffered some vision loss.
So says a Hong Kong researcher reporting in the March issue of Ophthalmology.
The case review is sure to ignite debate about the orthokeratology regimen, in which nearsighted patients are fitted with a series of rigid gas-permeable lenses to modify the shape of the cornea, in the process reducing or eliminating the nearsightedness.
While orthokeratology has been around since the 1960s, it is currently not as popular in the United States as it is in China, especially in Hong Kong, where up to 71 percent of the adult population is nearsighted. About 25 percent of the U.S. population aged 12 to 54 is believed to be nearsighted.
"More and more cases of corneal ulcer and infection in patients with overnight wearing of orthokeratology lenses are being reported," says study author Dr. Dennis S.C. Lam, chairman and professor of the Department of Ophthalmology and Visual Sciences at the Chinese University of Hong Kong.
"One has to weigh carefully the potential benefits and risks of orthokeratology lenses before choosing," he says.
He reports on six cases of corneal ulcers in children aged 9 to 14 years old, seen at his clinic from March 1999 to June 2001. All wore the lenses at night for eight to 12 hours. And the infections occurred three to 36 months after starting the regimen.
All had some vision loss after the ulcers healed, he adds.
Lam suspects the overnight wearing deprived the cornea of oxygen, boosting the risk of ulcer and infection. But it's not known if the lenses were made of material meant to be used for the orthokeratology regimen.
Other experts point out limitations of the study, but they also call for caution in using orthokeratology.
"We don't really know what the incidence of complications are," says Dr. Thomas L. Steinemann, an ophthalmologist at MetroHealth Medical Center Eye Clinic in Cleveland and a spokesman for the American Academy of Ophthalmology. He notes the study authors just reported on the cases of corneal ulcers they treated.
But corneal ulcers are potentially serious, he adds. "Any infection is significant, particularly when it involves the central cornea, which these did."
While the approach may have a role in a small group of patients, Steinemann says, "the effects [of the treatment] are not permanent."
Some eye experts point out the study has several variables that could affect the results.
"By the authors' own admission, we don't know the lens material," says Carmen Castellano, a St. Louis optometrist who is chairman of the American Optometric Association's Contact Lens and Cornea Section. They might have been lenses not meant for orthokeratology treatment, he says, adding, "We don't know totally the whole story."
Castellano fits children with the orthokeratology lenses if they are good candidates. The ideal candidate, he says, is faithful to cleaning and wearing regimens and has low to moderate nearsightedness. The lenses are worn on a continuous basis at night, he explains, "And then you can leave them out more and more" as the cornea is reshaped to correct the nearsightedness.
To keep the corrective effect, however, you must continue to wear the lenses at night, at least part time, depending on the degree of nearsightedness, Castellano says.
More information
For more information on contact lenses, visit the American Optometric Association and the American Academy of Ophthalmology.
