The contact lens and myopia progression (CLAMP) study: Design and baselinedata

Background. Although previous contact lens myopia control studies indicate that rigid contact lenses slow the progression of myopia in children, they have all suffered from limitations that challenge the significance of their results. The Contact Lens and Myopia Progression (CLAMP) Study addresses t he limitations of previous studies and attempts to correct them by implemen ting alternative Study designs. The CLAMP study also measures all the ocula r components to examine the potential mechanism of treatment effect. Method s. Eligible children were fitted with rigid gas-permeable contact lenses an d enrolled in a run-in period to determine whether they were able to adapt to rigid contact lens wear. Subjects who successfully completed the run-in period were randomly assigned to wear rigid contact lenses or soft contact lenses for the remainder of the 3-year study. The primary outcome measure w ill be the 3-year change in cycloplegic autorefraction; the secondary outco me measures will include the S-year change in axial length, peripheral auto refraction, crystalline lens curvatures, corneal curvature and thickness, a ccommodation, and intraocular pressure, which are being measured annually. Results. We examined 148 eligible subjects who participated in the run-in p eriod. Of the 148 eligible subjects, 116 (78.4%) were able to adapt to rigi d contact lens wear and were enrolled in the CLAMP Study. The mean age of t he participants at the baseline visit was 10.5 years, and 59.5% were girls. At the randomization visit, the mean (+/-SD) spherical equivalent refracti ve error in the right eye was -2.09 +/- 0.89 D, the mean central curvature of the right cornea by videokeratography was 44.5 +/- 1.3 D, and the mean a xial length of the right eye was 24.13 +/- 0.71 mm. Conclusions. Four of fi ve children aged 8- to 11-years-old were able to adapt to rigid gas-permeab le contact lens wear. The CLAMP Study aims to further clarify the effect of rigid gas-permeable contact lenses on myopia progression in children.