Abstract
Purpose :
Orthokeratology (OK) has been shown to be effective in controlling myopia progression. It is hypothesized that OK controls myopia progression by inducing relative positive power in the periphery of the cornea compared to the center. A prototype soft contact lens (SCL) was designed to simulate the optical impact of OK on the eye (simOK). The purpose of the study was to evaluate the efficacy of this lens for controlling myopia progression.
Methods :
The study was a multi-center, prospective, randomized, controlled trial with a two-arm, parallel-group design. Eligible subjects of any ethnicity who were between the age of 7 and 11 years and with myopia between -0.75D and -5.00D were randomly assigned to wear either investigational simOK SCL (test, T) or single-vision spectacle (control, C) lenses. Axial length (AL) and cycloplegic spherical equivalent autorefraction (SECAR) were measured at baseline, 6 months and 1 year. Both AL and SECAR were measured again in group T subjects after ceasing lens wear for a week to account for the impact of contact lens wear itself as opposed to its optics.
Results :
A total of 381 subjects from 10 multinational clinical sites were enrolled between 2014 and 2015, with 148 subjects in the T group and 147 in the C group completing 1-year follow-up. There were no significant differences in subject demographics or baseline characteristics (AL and SECAR) between the study groups. The average lens wear time (±SD) of subjects in group T was 11.49 (±2.19) hours/day and 6.09 (±0.88) days/week, which met compliance criteria. After 1 year of lens wear, the mean (± SE) change in AL from baseline was less in T (0.248±0.033mm) than C (0.273±0.033mm) group (T-C: -0.025mm, p=0.020). However, this difference was no longer statistically significant after the 1-week washout period (T-C: -0.019mm, p=0.071). Further, there was no significant difference in refraction change between the two groups (T-C: -0.051D, p=0.090).
Conclusions :
SCLs that simulate the optical impact of OK were largely ineffective in controlling myopia progression. These results are inconsistent with multiple reports of myopia control with OK, suggesting that the mechanism by which OK imparts myopia control may not be optical in nature. It also raises questions as to the choice of the control lens (SCLs vs. spectacles) in evaluating SCLs for myopia control.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.