The Berkeley Orthokeratology Study, Part II: Efficacy and duration.

Relative efficacy of orthokeratology (OK) was evaluated by assessing changes in refractive error, visual acuity, and corneal curvature in 31 treated and 28 randomized control subjects who wore conventional rigid contact lenses. The duration of changes was studied by monitoring subjects after lens wear was discontinued. After an average of 444 days of contact lens wear the treatment group showed an overall mean reduction in spherical equivalent refractive error of 1.01 D compared with 0.54 D in the control group (p = 0.02). Both groups had considerable variation in refractive error change. Corresponding mean improvements in unaided visual acuity were -0.27 and -0.20 log of the minimum angle of resolution [log (MAR)]. Corneal curvature decreased in both comparison groups, but the actual diopter value was about one-half that of the refractive change. The changes in these characteristics tended to occur during the first 132 days of wear, and additional aggressive lens therapy during the remaining 241 days of treatment produced little additional change. The refractive error fluctuated considerably during the period of follow-up and these fluctuations tended to be larger in those subjects who had shown greater changes in refractive error. When the lenses were removed, ocular characteristics returned steadily toward baseline levels. Ninety-five days after discontinuing lens wear, the refractive error had returned 75 and 69% of the way to baseline levels for the treatment and control groups, respectively. Visual acuity and corneal curvature showed similar rebound after 95 days. We conclude that it is possible to reduce myopia about 1D; however, the change is not permanent. Results indicate that the level of vision during periods of nonlens wear would be unstable, making it difficult to predict what the quality of vision would be under a retainer lens wear program.