The Berkeley Orthokeratology Study, Part I: General conduct of the study

The Berkeley Orthokeratology Study was a single center, randomized, concurrently controlled masked clinical trial. Eighty subjects were studied--40 in an orthokeratology (OK) treatment group and 40 in a control group fitted with conventional hard contact lenses. Visual and ocular characteristics were monitored for 1.5 years in order to assess relative efficacy, duration, and safety of the OK treatment. This report describes the general conduct of the study including recruitment methods, eligibility requirements, randomization and masking procedures, contact lens materials, and the treatment and follow-up plan. Baseline comparison revealed that the 21 subjects lost to follow-up were similar to the 59 subjects who completed follow-up and also that the 31 treatment and 28 control subjects in this group were quite similar in their baseline characteristics. In the course of adaptation and subsequent follow-up, treatment subjects were fitted with six lenses per eye on the average compared with three per eye in the control group. Analysis of lens prescriptions shows that the treatment lenses were substantially larger, thicker, and fitted optically flatter than those worn by the control group.