One-year results for myopia control with aspheric base curve orthokeratology lenses: A prospective randomised clinical trial

Purpose: To compare the effect of orthokeratology (ortho-k) using aspheric or spherical base curve (BCA vs. BCS) contact lenses on axial elongation and the relative peripheral refraction change (RPRC) in Chinese children. Methods: Children aged 8-12 years with myopia between - 0.75 and - 4.00 D and astigmatism <= 1.00 D were randomly assigned to the BCA or BCS group. Peripheral refraction was assessed at 10 degrees, 20 degrees and 30 degrees along the temporal and nasal retina at baseline and at the 12-month visit. Axial length (AL) was measured under cycloplegia at baseline and at the 6- and 12-month visits. Only right eye data were analysed. Repeated-measures analysis of covariance was performed to examine the differences in axial elongation and the RPRC between the BCA and BCS groups. Results: The 1-year results from 31 BCA and 32 BCS subjects were analysed. No significant between-group differences were found at baseline (p = 0.28). At the 12-month visit, the BCA lens produced a greater absolute RPRC along the horizontal meridian than the BCS lens (p < 0.001). Axial elongation was slower in the BCA group (0.19 +/- 0.20 mm) than in the BCS group (0.29 +/- 0.14 mm; p = 0.03). Axial elongation was correlated with the RPRC at 10 degrees (r = 0.43, p = 0.02) and 20 degrees (r = 0.39, p = 0.03) along the temporal retina in the BCA group; however, these correlations were not observed in the BCS group. Conclusion: The BCA ortho-k lens could improve the efficacy of slowing axial elongation in children. The improved myopia control observed in the BCA group may be the result of a larger myopic shift in relative peripheral refraction within 20 degrees along the temporal retina.