Orthokeratology : Compendium of latest research


CLAMP Study - To examine the effects of rigid gas permeable contact lenses on the progression of myopia in children.

This US study evaluated how short-sightedness developed in 116 children aged 8-11 who were randomly assigned either conventional rigid gas permeable (RGP) or soft contact lenses based on a theory that conventional RGP lenses demonstrated a capability to slow down the subsequent development of short-sight. After three years, the results showed that whilst all children had continued to experience further deterioration in the short-sightedness, those wearing conventional RGP lenses had suffered over half a diopter less of deterioration than the children who wore conventional soft lenses. Whilst not specifically relating to Overnight Vision Correction (OVC), the importance of this study is in confirming that RGP lenses can slow down the progression of short-sightedness. (OVC lenses are made from RGP material.)

                                                                                                                                                                                                                                          OBJECTIVE: To compare the effects of rigid gas permeable
 contact lenses (RGPs) and soft contact lenses (SCLs) on myopia progression in children.
METHOD: We randomly assigned 116 subjects to wear RGPs or SCLs. Subjects underwent cycloplegic autorefraction, keratometry, and A-scan ultrasonographic axial length measurements at each annual visit. All analyses were con- ducted according to the original randomization assignment. The primary outcome measure was the 3-year change in spherical equivalent cycloplegic autorefraction. 

RESULTS:  The mean ± SD spherical equivalent cyclople- gic refractive error progressed -1.56 ± 0.95 diopters (D) for RGP wearers and -2.19 ± 0.89 D for the SCL wearers during the 3 years of the study (analysis of covariance [ANCOVA], P􏰀.001). The axial growth of the eyes was not significantly different between treatment groups (ANCOVA, P = .57). The steep corneal meridian of the RGP wearers steepened 0.62 ± 0.60 D, and that of the SCL wearerssteepened 0.88 ± 0.57 D during the 3 years (ANCOVA, P = .01).
CONCLUSION: The RGP wearers' myopia progressed less than that of the SCL wearers. The corneal curvature of the SCL wearers steepened more than that of the RGP wearers, but the axial growth was not significantly different between the groups. Most refractive error treatment effect was limited to the first year of the trial. The results of the study provide information for eye care practitioners to share with their patients, but they do not indicate that RGPs should be prescribed primarily for myopia control. Arch Ophthalmol . 2004;122:1760-1766 
October 15, 2009, National Eye Institute (NEI), The Contact Lens and Myopia Progression (CLAMP) Study. A Randomized Trial of the Effects
of Rigid Contact Lenses on Myopia Progression
Jeffrey J. Walline, OD, PhD; Lisa A. Jones, PhD; Donald O. Mutti, OD, PhD; Karla Zadnik, OD, PhD
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