Novel quantitative analysis of relative peripheral refraction changes in orthokeratology and their relationship with one-year axial elongation

Purpose

To investigate changes in relative peripheral refraction (RPR) and their associations with axial length (AL) growth after one year of orthokeratology (ortho-k) therapy.

Methods

This prospective cohort study included 60 myopic children aged 8–15 years. RPR and AL were measured at baseline and 12 months after ortho-k therapy. Total RPR was measured via multispectral refraction topography (MRT) in the 53° fundus field of view, and then was divided into specific annuli (0–10°, 10–20°, 20–30°, 30–40°, 40–50° and 50–53°) and quadrants (superior, inferior, temporal and nasal). Linear regression analyses quantified associations between RPR changes and AL elongation.

Results

Ultimately, 80.0 % of the participants were analysed. The total RPR was 0.64 ± 0.26 D at baseline and -0.35 ± 0.64 D at 12 months. Ortho-k therapy induced myopic shifts in all subregions (all p < 0.05). Additionally, hyperopic RPRs within the 50° region and in the superior, inferior and nasal parts of the retina became myopic. These myopes had an asymmetric RPR in the vertical retina both before and after ortho-k treatment but a symmetric RPR in the horizontal retina, which changed after treatment. Multivariate linear regression analyses revealed that the baseline AL and RPR changes in the 30–40° region and in the inferior retina were independently associated with AL elongation during one-year of ortho-k lens wear (all p < 0.05).

Conclusions

The more myopic shifts of RPR induced by ortho-k treatment in the 30° to 40° region and in the inferior retina, the more effective control of axial elongation.