Axial Growth and Meridian Modulation of Cornea Power in Children Wearing Orthokeratology Lenses of Different Back Optic Zone Diameters

Purpose: To evaluate the effect of orthokeratology lenses with different back optical zone diameters (BOZD) on relative corneal refraction power shift (RCRPS) and explore its association with axial length growth (ALG). Design: A randomized, double-blinded, controlled clinical trial. Methods: Subjects aged between 8 and 15 years, with the refraction of −1.00 to −4.00 D. Participants were randomly assigned to two groups, wearing a BOZD_5.0 mm or a BOZD_6.2 mm lens. Axial length (AL) was measured at baseline and 12 months after lens wear, and ALG and age-adjusted ALG (aALG) were calculated. A differential map comparing the 12-month and baseline corneal topography was used to analyze the RCRPS, summed within the central 4 mm diameter. The RCRPS subset was divided into eight meridians at 45° intervals. Linear and stepwise multiple linear regression were performed to assess the associations between ALG and RCRPS. Results: There was no significant difference in baseline parameters, including age, spherical equivalent, and AL (all P > .05). Over 12 months, children wearing BOZD_5.0 mm lens demonstrated significantly slower ALG (0.15 ± 0.13 mm) than those wearing BOZD_6.2 mm lenses (0.24 ± 0.17 mm, P = .04). aALG was also significantly slower in BOZD_5.0 mm group (−0.10 ± 0.12 mm vs −0.001 ± 0.16 mm, P = .01). The summed RCRPS within the central 4 mm area was significantly greater in children wearing BOZD_5.0 mm lenses (92.31 ± 43.21 D) when compared to children wearing BOZD_6.2 mm lenses (70.04 ± 41.64 D, P = .04). The summed RCRPS only demonstrated significant differences between the groups on 0°, 45°, and 90° meridians (all P < .01). The association between aALG and summed RCRPS was analyzed on eight different meridians. Only the 0°, 45°, and 90° meridians demonstrated significant associations. Conclusions: Children wearing orthokeratology lenses with smaller BOZD had slower ALG. This difference in ALG was associated with greater RCRPS in the nasal-superior quadrant of the cornea.