Purpose: To determine ocular optical parameters that affect axial length elongation in myopic children undergoing overnight orthokeratology.
Design: Prospective, noncomparative study.
Participants: Fifty-nine subjects who met the inclusion criteria were enrolled in this study.
Methods: Axial length and ocular wavefront aberration were assessed before and 1 year after the start of orthokeratology. Corneal topography was performed, and then corneal multifocality was calculated for a 4-mm pupil. After evaluating simple correlations between axial elongation and optical parameters, multiple linear regression analysis was performed to identify explanatory variables with a statistically significant contribution to axial elongation.
Main outcome measures: Axial length and ocular wavefront aberration before and 1 year after the start of orthokeratology.
Results: Fifty-five subjects completed the 1-year follow-up examinations. At baseline, their age ranged from 7.2 to 12.0 years. The manifest spherical equivalent refractive error ranged from -3.50 to -0.75 diopters. The mean axial length significantly increased from 24.20 mm at baseline to 24.43 mm 1 year after treatment. The axial elongation showed significant simple correlations with the change in C2(0), change in second-order aberration, change in coma-like aberration, change in spherical-like aberration, change in total higher-order aberrations, change in corneal multifocality, baseline age, and baseline spherical equivalent refractive error, but not C4(0). Multiple linear regression analysis showed that the change in coma-like aberration was the most relevant variable.
Conclusions: Asymmetric corneal shapes, rather than concentric and radially symmetric shapes, have a considerable effect on retardation of axial elongation, suggesting that the inhibitory effect of orthokeratology on myopia progression is caused by mechanisms other than the reduction in peripheral hyperopic defocus.
Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.