Changes in horizontal and vertical peripheral refraction and their predictive value for myopia control after orthokeratology: a 2-year prospective study.

PURPOSE: To investigate changes in peripheral refraction in both horizontal and vertical meridians after long-term orthokeratology and their correlation with axial elongation (AE). METHODS: Children aged 8 to 14 years were fitted with orthokeratology lenses. Axial length and peripheral refraction, from 12 locations in the horizontal and vertical meridians, were measured at baseline and every 6 months over the study period. RESULTS: 39 subjects were recruited, with a mean AE of 0.38 ± 0.17 mm at 24 months. Except superior 5° (S5°), relative peripheral refraction (RPR) showed significant myopic defocus at all locations (all p ≤ 0.003) after orthokeratology. Except temporal 20° (T20°) and 30° (T30°), peripheral vertical (90°)/horizontal (180°) astigmatism component (J0) changed significantly (all p ≤ 0.045) and except nasal 30° (N30°), peripheral oblique (45° and 135°) astigmatism component (J45) changed significantly (all p ≤ 0.022). Except 18 months, the AE of each follow-up was negatively correlated with J0 at inferior 5° (I5°) (r = -0.371, -0.364, -0.496, p = 0.033, 0.041, 0.007, respectively), J45 at N10° (r = -0.401, -0.348, -0.417, p = 0.019, 0.048, 0.024, respectively) and I10° (r = -0.415, -0.512, -0.471, p = 0.018, 0.003, 0.011, respectively), as measured at 6 months. The 18-month AE was only negatively correlated with the 6-month J45 at I10° (r = -0.415, p = 0.031). Multiple linear regression models were established to assess the relationship between AE and the 6-month J0 at I5°, J45 at N10°, J45 at I10° (r 2 = 0.340, 0.336, 0.263, 0.430, p = 0.010, 0.013, 0.077, 0.004, respectively). CONCLUSION: Significant changes in RPR, J0 and J45 were observed at most locations in the horizontal and vertical meridians after orthokeratology. Partial peripheral astigmatism components measured at 6 months demonstrated significant predictive value for the long-term efficacy of orthokeratology in myopia control.