Use of a run-in period to decrease loss to follow-up in the contact lens and myopia progression (CLAMP) study

Rigid gas permeable (RGP) contact lenses are initially less comfortable to wear than spectacles. In previous studies evaluating the use of RGP contact lenses to control myopia, more subjects randomly assigned to wear RGP contact lenses have been lost to follow-up than spectacle wearers. Previous rigid contact lens myopia control studies have lost 44% and 47% of the rigid contact lens wearers. This unequal loss to follow-up may compromise the results of the study, so we conducted a run-in period prior to randomized treatment-group assignment to ensure that all participants could adapt to RGP contact lens wear. We enrolled 147 children ages 8–11 years with myopia in the run-in period. Of the 147 subjects, 116 (78.9%) were able to wear RGP contact lenses for at least 40 hours per week and reported that they were “usually comfortable” or “always comfortable.” After 3 years, no subjects were lost to follow-up. The run-in period greatly reduced the loss to follow-up suffered by previous RGP contact lens myopia progression studies and may help provide more definitive answers regarding myopia control with RGP contact lenses.