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17 Jun 2002
Wearing a special kind of contact lens while sleeping may help a nearsighted person go without contacts or glasses during the day.
After just seven nights of wearing reverse-geometry gas permeable contact lenses, researchers saw improvement in the daytime eyesight of seven out of eight nearsighted - or myopic - subjects. By the end of the 60-day trial, all of the subjects could see clearly during the day without the use of contacts or glasses.
"Wearing these lenses overnight is an effective way to temporarily reduce myopia," said Joseph Barr, a co-author of the study and a professor of optometry at Ohio State University.
"It took about three weeks to get the desired effect in visual improvement," Barr said. "Once that happened, the changes in vision were maintained over the course of an 8-hour workday."
None of the subjects in the current study was severely myopic. Also, they had either little or no astigmatism - an irregular curve in the cornea that distorts an image. The subjects were asked to wear rigid gas permeable lenses every night of the study. Unlike the traditional convex shape of contact lenses, reverse geometry lenses get steeper around the central part of the contact and then flatten out at the edges.
Gas permeable lenses are made of hard plastic and have microscopic pores that allow oxygen to reach the eye. The lenses are also hard enough to change the shape of the cornea. In this study, the reverse geometry lenses flattened the cornea.
"When the participants took the lenses out, their corneas were shaped like they had undergone refractive surgery," Barr said.
But the effects of these lenses aren't permanent. "If a patient discontinues wearing these lenses, their vision will regress back to what it was," Barr said. NA
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