Dec. 24, 2004 COLUMBUS, Ohio – New research suggests that rigid gas permeable contact lenses may help slow the progression of nearsightedness, or myopia, in young children.
At the end of a three-year study of more than a hundred 8- to 11-year olds, researchers determined that wearing rigid gas permeable (RGP) contact lenses slowed the progression of myopia by nearly 30 percent, compared to soft contact lens wear.
Only recently did researchers find that young children could handle the responsibility of wearing contact lenses.
The corneas of the rigid contact lens wearers did not change as much as those of the soft contact lens wearers. This difference, which is not thought to be a permanent change, explains part of the difference between the RGP and soft contact lens wearers, said Jeffrey Walline, the study's lead author and an adjunct assistant professor of optometry at Ohio State University.
He and his colleagues caution that the RGP lenses won't stop myopia in its tracks, and also that the effects of these lenses probably aren't permanent. But the researchers also say that RGP lenses could be a good option for nearsighted children who can adapt to wearing them.
"Severe myopia, which is fairly rare, can lead to a detached retina and permanent vision loss or glaucoma," Walline said. "Theoretically, wearing RGP contact lenses could lessen the severity of myopia, and likewise the chances of developing one of these problems.
"But it's also a matter of convenience – keeping myopia's progression in check may mean that a child can see his bedside clock, or walk to the bathroom in the middle of the night without having to depend on glasses."
The study appears in the December 2004 issue of the journal Archives of Opthalmology.
While myopia can develop at any age, it most often begins during childhood, around ages 6 to 8. Progression typically slows by the mid-teens.
The researchers evaluated 116 children who participated in the Contact Lens and Myopia Progression (CLAMP) Study at Ohio State. All children were given about two months to adapt to wearing the rigid contact lenses before the study officially began.
"It takes most children about two weeks to get used to this type of contact lens," Walline said. "We wanted to make sure the children could wear the rigid lenses for the long-term."
At the end of the two-month initiation period, children were randomly assigned to wear RGP contact lenses or two-week disposable soft contact lenses. Children returned to the optometry clinic each year for three years for annual vision checkups.
A nearsighted eye is typically longer than a normal eye, which results in blurred vision when looking at distant objects.
"To have a permanent effect, contact lenses would ideally slow the growth of the eyeball," Walline said. "The RGP contact lenses did not do that. However, they did maintain the shape of the cornea, whereas the cornea of the soft contact lens wearers became more curved. This increased corneal curve resulted in more myopia in the group that wore soft contact lenses."
The children in both groups wore their lenses an average of 70 hours a week. The researchers aren't sure how many hours a day a child would have to wear RGP lenses in order to slow the progression of nearsightedness.
"Rigid contact lenses may offer visual and eye health benefits that many soft contact lenses don't," Walline said. "These harder lenses allow more oxygen to reach the cornea than do most soft contact lenses, and they do a better job of correcting astigmatism.
"These factors, in addition to the modest myopia control, should be weighed against the initial discomfort that sometimes goes along with RGP lens wear when deciding what a child should use to correct his vision problems."
The current study also suggests that about four out of five children can adapt to wearing RGP lenses, which cost about $160 a year, Walline said. For comparison, disposable contact lenses – like the kind used in this study – cost about $260 a year.
Walline conducted the CLAMP study with Ohio State optometry colleagues Lisa Jones, Donald Mutti and Karla Zadnik, the Glenn A. Fry professor of optometry.
The CLAMP Study received funding from the National Eye Institute; Menicon Co, Ltd, CIBA Vision Corporation, and SOLA Optical – all contact lens manufacturers; and an American Optometric Foundation William C. Ezell Fellowship. The authors have no relevant financial interest in the sponsors of the study.
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