Add-On Effect of 0.01% Atropine in Orthokeratology Wearers for Myopia Control in Children: A 2-Year Retrospective Study

Introduction Orthokeratology (OK) and low-concentration atropine are recommended approaches for controlling myopia. However, children with younger age and lower myopia are more likely to experience rapid axial progression during OK or atropine monotreatment. This study aimed to assess the efficacy of OK combined with low-concentration atropine for myopia control in children over 24 months and to determine whether the effect was sustainable. Methods In this retrospective study, we reviewed medical records of baseline and follow-up visits from children (7–14 years) applying OK for myopia control. Sixty-eight children receiving monoorthokeratology treatment (OK group) and 68 children who received 0.01% atropine in combination with orthokeratology simultaneously (AOK group) were included. A series of ophthalmic tests at baseline were conducted, and axial length (AL) was measured every 6 months. The comparison of AL change at different visits between the two groups was performed by repeated measures multivariate analyses of variance (RM–MANOVA). Results There were no significant differences in baseline characters between the two groups ( p > 0.05). The AL significantly increased over time in both groups (all p < 0.05), and the 2-year change in AOK was 0.16 mm (36%) lower than in OK (0.28 ± 0.22 mm versus 0.44 ± 0.34 mm, p = 0.001). Compared with OK group, the significant suppression of AL elongation in the AOK group was observed in 0–6, 6–12, and 12–18 month periods (suppression rate: 62.5%, 33.3%, 38.5%, respectively, p < 0.05), while there was no significant difference in the 18–24 month period ( p = 0.105). The multiple regression analysis showed an interaction between age and treatment effect (interaction coefficient = 0.06, p = 0.040), indicating one year age decrease approximately associated with 0.06 mm increased retardation in AL elongation in the AOK group. Conclusion The add-on effect of 0.01% atropine in OK wearers only occurred within 1.5 years, and younger children benefited more from the combination treatment.