The approach uses a rigid, gas-permeable contact lens to flatten the cornea, temporarily correcting nearsightedness. The concept, called orthokeratology, has been around for decades, said Dr. Jeffrey J. Walline, a research scientist at Ohio State University, Columbus, who led the children's orthokeratology study.

But the US Food and Drug Administration (news - web sites) (FDA) approved an overnight lens for the temporary reduction of nearsightedness in June 2002, granting the approval to Paragon Vision Sciences in Mesa, Arizona for its CRT (corneal refractive therapy) and Quadra RG lenses. The lens can be used in both adults and children, under the device approval granted by the FDA.

Previously, lenses for orthokeratology treatment were only approved for daytime wear, an approach considered to be not as convenient as overnight wear, Walline said.

Walline's study was conducted prior to the FDA approval, in an effort to determine the safety and effectiveness of the special lens use in children. He fit 25 children, aged 8 to 11, with the lenses and instructed them to wear the lenses each night while sleeping. Their vision was measured regularly for 6 months after they began the overnight wearing regimen.

Before the children started the study, they all wore glasses to correct their vision, and all were mildly to moderately nearsighted. "We fit them with the overnight orthokeratology contact lenses so they would have clear vision throughout the entire day without contact lenses or glasses," Walline said.

"In about 2 weeks, after wearing these lenses overnight every night during sleeping hours, they could do without their glasses during the day. Their vision might decline a little at the end of the day," he added.

At the meeting, Walline reported that the 10 children who have thus far completed 6 months of the study can make it through the day without eyeglasses or contact lenses.

The lenses used for orthokeratology are shaped differently than conventional contact lenses, Walline explained, allowing them to change the shape of the cornea more quickly. The lenses flatten the cornea so light rays focus on the retina as they should, thus sharpening vision.

The best candidates for the approach, Walline noted, are children with moderate nearsightedness, less than five diopters, or roughly 20/400 vision. The FDA approval is for those with up to six diopters, however. Nearsighted children who also have low amounts of astigmatism (an abnormality of the eye that results in blurred images) can also be fitted.

The first-year cost, including lenses and fittings, is about $1,000, Walline estimates. Walline pointed out that the approach is not a permanent remedy for nearsightedness. "We're treating it but not curing it."

Support for the study was received from Paragon Vision Sciences, the maker of the lenses, and a grant from the American Optometric Association. The overnight contacts carry the same risks as other rigid gas-permeable lenses, including a chance of corneal swelling and corneal staining, according to the company.

Dr. Robert Davis, a practicing optometrist in Oak Lawn, Illinois and former chair of the American Optometric Association's contact lens and cornea section, thinks the approach will take off, particularly for children.

"For kids involved in sports, it will be a significant advantage," said Davis, who is studying the approach for another manufacturer. Wearing the rigid gas-permeable lenses, typically not as comfortable as conventional soft lenses, poses less of a comfort problem if worn at night rather than during the day, he said.

Recent improvements in rigid contact lens materials have made them more comfortable and also makes the orthokeratology approach more feasible, added Dr. Glenda Secor, a Huntington Beach, California-based optometrist who is also studying the approach for another manufacturer. Like Davis, she said the approach is worth a try if children are willing to wear the lenses nightly.

"The good news is, it's not permanent," she told Reuters Health. "The bad news is, it's not permanent."