Nearsighted children may benefit from rigid contact lenses
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. Rigid contact lenses alter the shape of the cornea, which plays a small role in the development of myopia, said Jeffrey Walline, the studys lead author and an adjunct assistant professor of optometry at Ohio State University.
He and his colleagues caution that the RGP lenses wont stop myopia in its tracks, and also that the effects of these lenses probably arent 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 lenses could lessen the severity of myopia, and likewise the chances of developing one of these problems.
"But its also a matter of convenience – keeping myopias 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 8 to 14. Progression typically slows by the mid-teens for females and by the mid-20s for males.
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 handle the rigid lenses for the long-term."
At the end of the two-month initiation period, children were randomly assigned to wearing RGP lenses or two-week disposable soft contact lenses. Children returned to the optometry clinic each year for three years for annual vision checkups.
A normal eyeball is round, while a nearsighted eye is shaped like an egg – somewhat oval. This irregular shape is the most common cause of nearsightedness. "To have a permanent effect, contact lenses would ideally control the shape of the eyeball as it grows," Walline said. "The RGP lenses did not do that. However, they did change the shape of the cornea on a short-term basis."
While the cornea plays a small role in myopias development, the RGP lenses were able to change the corneas shape enough to lessen myopias progression by 28.8 percent. The rigid contact lenses kept a condition called "corneal steepening" to a minimum – because the nearsighted eye takes on a more oval shape, the cornea becomes steeper than that of a normal, round eye.
Soft contact lenses had no effect on the shape of the cornea, or on the progression of myopia.
The children in both groups wore their lenses an average of 70 hours a week. The researchers arent 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 soft contact lenses dont," Walline said. "These harder lenses allow more oxygen to reach the cornea than do most soft contacts, and they do a better job controlling 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."
Previous studies suggest 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.
CLAMP 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.
Jeffrey Walline | EurekAlert!