The change of regional relative peripheral refraction after orthokeratology and its correlation with corneal...

To assess relative peripheral refraction (RPR) regionally before and after orthokeratology (OK) using the Refraction Topographer (RT) and analyze the relationship between changes in RPR and corneal reshaping parameters.

This is a prospective, non-randomized, controlled study. Subjects chose either OK or single-vision spectacles (SVS) based on preference and were assigned to the OK or SVS group. Regional RPR was measured at baseline (pre-wearing) and 2 months later (post-wearing) in both groups. The increased curvature of high convex zone compared to the treatment zone (ICH) was calculated to quantify the prominence of high convex zone.

Forty-one subjects (mean age: 9.93 ± 1.66) were enrolled in the OK group and 20 (mean age: 10.10 ± 1.62) in the SVS group. Only right eyes were included when myopia was bilateral. At baseline, there were no significant differences in age, gender, refractive error or axial length between groups. After 2 months, no significant changes in RPR in any region were found in the SVS group. The OK group showed significant myopic shift in RPR in regions between 15° and 30° visual field (-0.35 ± 0.35D), 30° and 45° (-0.96 ± 0.84D), 45° and 53° (-1.68 ± 1.41D), temporal quadrant (-1.47 ± 1.14D), inferior quadrant (-1.39 ± 1.22D), and superior quadrant (-0.57 ± 0.89D) (all p < 0.05). The shift was more pronounced towards the periphery (p < 0.001) and in the temporal and inferior quadrants (p < 0.01). Additionally, the change in RPR across the whole detection field was significantly correlated with baseline Spherical Equivalent Refractive (r = 0.47, p = 0.002) and ICH (r = -0.51, p = 0.001).

After OK, relative peripheral myopic defocus significantly increased in all regions between 15° and 53° visual field, except the nasal quadrant. The increase was more pronounced in the periphery and in the temporal and inferior quadrants. Additionally, as the degree of myopia increased, the high convex zone became more prominent, leading to a greater increase in relative peripheral myopic defocus.