Axial Length Control Using Repeated Low-Level Red Light Combined with Orthokeratology Compared with Orthokeratology Alone in Rapidly Progressing Myopic Children.

Purpose: To evaluate the efficacy and safety of combining repeated low-level red light (RLRL) therapy with orthokeratology (OK) in slowing axial elongation in children with rapid myopia progression. Patients and Methods: This retrospective cohort included 72 children aged 8-14 years (RLRL+OK, n=36; OK-only, n=36) meeting the rapid-progressor definition (>0.40 mm/year axial elongation. One eye per child was randomly selected. Axial length (AL) was measured at baseline and at 3, 6, and 12 months. Inverse probability of treatment weighting (IPTW) based on age, sex, and baseline AL achieved good balance between groups. The primary outcome was the 12-month AL change, assessed using IPTW-weighted linear mixed-effects models adjusted for covariates. Prespecified subgroup analyses were stratified by age (<10 vs ≥10 years). Sensitivity analyses included propensity score matching (PSM), per-protocol analysis (PP; adherence ≥80%), and dose-response evaluation. Safety was assessed using slit-lamp biomicroscopy and macular OCT imaging. Results: At 12 months, the RLRL+OK group had significantly less elongation than OK-only (mean difference -0.298 mm; 95% CI -0.388 to -0.209; p<0.001), with significant group×time interactions from 3 months. Benefits were consistent across age subgroups without effect modification. Sensitivity analyses confirmed robustness: PSM (-0.255 mm; p<0.001) and PP (-0.298 mm; p<0.001). Dose-response showed each 10% higher adherence reduced elongation by -0.148 mm (p<0.001). No clinically significant adverse events were detected. Conclusion: RLRL combined with OK significantly reduced axial elongation in rapid-progressing children compared with OK alone, with a clear adherence-dependent effect and reassuring short-term safety profile.