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Helen A. Swarbrick, Ahmed Alharbi, Edward Lum, Kathleen Watt; Changes in Axial Length and Refractive Error During Overnight Orthokeratology for Myopia Control. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2837.
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To investigate changes in axial length and refractive error during overnight orthokeratology (OK) compared with conventional daily rigid gas-permeable (GP) contact lens wear in myopic children.
Twenty-six children (10.5 to 16.7 years) with progressive myopia wore an overnight OK lens in one eye and a GP lens for daily wear in the other eye for one year. After 6 months the lens-eye combinations were reversed. Axial length was monitored using the IOL Master. Spherical equivalent refractive error was measured using the Shin-Nippon NVision-K 5001 autorefractor at baseline and after a 2-week washout period of no lens wear at 6 and 12 months. Changes in axial length and refractive error were analysed separately over the two study phases, relative to baseline data collected at the beginning of each 6-month period. ANOVA and post hoc paired t-tests were used to compare changes in the two eyes. The relationship between axial length and refractive error changes was analyzed using Pearson correlation.
Differences in axial length growth between OK and GP eyes were statistically significant at 6 months (GP-OK: 0.05±0.12mm, p<0.05) and 12 months (0.09±0.17mm, p<0.005). Significant interocular differences in refractive error were also found after a 2-week washout at 6 months (GP-OK: -0.32±0.45D, p<0.005) and 12 months (-0.57±0.66D, p<0.005). Increases in axial length and myopic refractive error in the GP eye were significantly correlated (r=-0.698, p<0.001), whereas correlation between these variables in the OK eye did not reach statistical significance.
Overnight OK lens wear inhibits axial length growth and myopia progression over a 12-month period. After 6 and 12 months the OK eye showed no change in axial length and a slight decrease in myopia compared to baseline, whereas the GP eye showed axial length growth and myopia progression. Crossover of the effects on axial length and refractive error after reversal of lens-eye combinations at 6 months reinforces the promise of this modality for myopia control.
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