COLUMBUS, Ohio -- 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. The study appears in a recent issue of the journal Optometry and Vision Science.
"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 were 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 during at least seven hours of sleep. 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. Refractive surgery uses either a laser or a knife to permanently reshape the corneas of a nearsighted person.
The researchers examined the eight subjects five times during the 60-day study: on days one, seven, 14, 30 and 60. Each underwent a vision test immediately after taking out the contacts and again one, four and eight hours after taking out the contacts.
"Most of the improvement occurred during the first seven nights of lens wear," Barr said. "Daytime vision continued to improve beyond the seventh night, and tended to level off around day 30."
The reverse geometry lenses range in price from $1,250 to $2,500 for a year's worth of treatment -- about half the cost of refractive surgery in the United States, according to Barr. 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.
The point of using reverse geometry lenses is that a mildly nearsighted person would not have to undergo laser surgery to correct her vision. Also, Barr said, some people could get by with wearing the lenses every two to three nights.
"While the FDA has approved reverse geometry lenses for daytime wear, there has been no approval for nighttime wear," Barr said. "The FDA has given us permission to conduct more studies to test the safety and effectiveness of wearing these lenses while sleeping."
Wearing contact lenses during sleep causes the cornea to swell a little more than it normally does. It also cuts in half the amount of oxygen that reaches the cornea, Barr said. Two subjects dropped out of the study because of discomfort. Even so, the majority of patients had no significant complaints.
"There are gas permeable materials that are safe enough to be slept in, as well as materials that are approved for extended wear," Barr said. "Besides, rigid gas permeable contacts allow more oxygen in than do extended wear soft contact lenses."
Barr collaborated in the study with Jason Nichols, Matthew Marsich, Myhanh Nguyen, all students in the College of Optometry at Ohio State; and Mark Bullimore, an associate professor of optometry at Ohio State. The research was supported by a grant from Beta Sigma Kappa and the National Eye Institute.
Written by Holly Wagner, 614-292-8310
Wagner.235@osu.edu
Journal
Optometry and Vision Science