Gas permeable contact lenses can slow myopia progression among children by as much as half, compared with soft contact lenses, according to new results from the Contact Lens and Myopia Progression (CLAMP) Study.

We assume that if the rigid contact lenses slowed the progression of nearsightedness significantly (for example, cut the progression in half), then the standard of care may have changed, and most kids would be fitted with rigid contact lenses rather than soft contact lenses, says principal investigator Jeffrey J. Walline, O.D., Ph.D., of the Ohio State University College of Optometry.

However, these results do not mean that children should be fit with GPs solely to control myopia, Dr. Walline says.

Parents who want rigid contact lenses for their child solely because they believe they slow the progression of nearsightedness should be educated that while they slow the progression slightly, the effect is not likely to be permanent, he says. Other treatment options should be considered along with rigid gas permeable contact lenses.

In the study, OSU investigators evaluated 116 children (ages 8 to 11). After an adaptation period of at least two months in GP wear, half of the children were assigned to GP lenses and half to soft contact lenses (SCL). At the end of the three-year study, the mean refractive error progressed -1.56D (0.95D) in GP wearers and -2.19D (0.89D) in SCL wearers.

Interestingly, although myopia progression of GP wearers was about half of the progression of SCL wearers over the first year, the two groups progressed nearly equally over the last two years of the study, Dr. Walline says. This phenomenon has occurred in other myopia control studies, but the reason for this is unknown, he says.

Indeed, several such factors lead to questions about the permanency of the treatment effect. For instance:

A portion of the effect is likely to be due to corneal flattening that may be reversible.
Decreased refractive error progression is not accompanied by slowed axial growth.

Data from this study do not warrant the fitting of myopic children with RGPs solely for the purpose of significant myopia control, the authors conclude. But they do provide reliable information that eye care practitioners can use to counsel their patients on myopia control.

Walline JJ, Jones LA, Mutti DO, Zadnik K. A randomized trial of the effects of rigid contact lenses on myopia progression. Arch Ophthalmol 2004 Dec;122(12):1760-6.