Purpose To investigate the 2-year efficacy of atropine, orthokeratology (ortho-k) and combined treatment on myopia. To explore the factors influencing the efficacy.

Methods An age-stratified randomised controlled trial. Children (n=164) aged 8–12 years with spherical equivalent refraction of −1.00 to −6.00 D were stratified into two age subgroups and randomly assigned to receive placebo drops+spectacles (control), 0.01% atropine+spectacles (atropine), ortho-k+placebo (ortho-k) or combined treatment. Axial length was measured at baseline and visits at 6, 12, 18 and 24 months. The primary analysis was done following the criteria of intention to treat, which included all randomised subjects.

Results All interventions can significantly reduce axial elongation at all visits (all p<0.05). Overall, the 2-year axial elongation was significantly reduced in combined treatment than in monotherapies (all p<0.05). After stratification by age, in the subgroup aged 8–10, the difference between combined treatment and ortho-k became insignificant (p=0.106), while in the subgroup aged 10–12, the difference between combined treatment and atropine became insignificant (p=0.121). A significant age-dependent effect existed in the ortho-k group versus the control group (p for interaction=0.013), and a significant age-dependent effect existed in the ortho-k group versus the atropine group (p for interaction=0.035), which indicated that ortho-k can achieve better efficacy in younger children.

Conclusions Atropine combined with ortho-k treatment can improve the efficacy of myopia control compared with monotherapy in children aged 8–12. Younger children might benefit more from ortho-k.

Trial registration number ChiCTR1800015541.