Efficacy of different optical zone design with different myopia control for corneal refractive therapy (CRT): a one-year prospective cohort study

This study aims to compare the one-year myopia control effects of orthokeratology (OK) lenses with different optical zone designs in children with varying degrees of myopia. A total of 200 children with myopia aged 7–12 years with spherical equivalent refraction (SER) ranging from − 0.50 D to − 6.00 D were enrolled. They were non-randomly divided into four groups based on the baseline refractive power and the final choice on OK lenses type: Low myopia 6.0 group, Mod myopia 6.0 group, Low myopia 5.0 group, and Mod myopia 5.0 group, with 50 children in each group. Data from the right eye were used for analysis. We comparatively analysed the one-year follow-up axial length (AL) and AL elongation between each group. We also analyzed the interaction effect between different optical center designs and different initial myopic refractive powers on AL elongation over 1 year by two-way ANOVA, and compared the proportions of non-progressive myopia among the four groups. At the 1-year follow-up, AL differed significantly across different myopia subgroups, with Mod myopia groups showing longer AL than low myopia groups, but no significant difference was noted between lens design subgroups. For one-year AL elongation, subgroups with small optical zone designs and those with initial moderate myopia had lower values. A slight interaction effect was observed between lens optical center design and initial myopia severity ( F = 6.700, P = 0.010, partial η² =0.033). The one-year AL elongation was 0.280 ± 0.170, 0.148 ± 0.167, 0.154 ± 0.121, and 0.141 ± 0.185 in Low Myopia 6.0 group, Mod Myopia 6.0 group, Low Myopia 5.0 group, and Mod Myopia 5.0 group, respectively; the corresponding non-progressive myopia rates were 62%, 36%, 58%, and 64%. The Mod Myopia 5.0 group presented the slowest AL elongation and the highest non-progressive myopia rate, whereas Mod myopia 6.0 group and Low myopia 5.0 group also showed slower AL elongation and higher non-progressive myopia rates than those of the Low myopia 6.0 group. CRT lenses with a small optical zone design exhibited better myopia control compared to those with a larger optical zone design, especially in children with low myopia.