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.