Axial Elongation Suppression with Nightly 0.01% Atropine in Adolescents: A Mixed-Effects Longitudinal Analysis from a Randomised Trial

Objectives: This trial conducted a comparison between once-nightly instillation of 0.01% atropine eye drops and placebo to suppress axial elongation of progressive myopia in adolescents. Method: A parallel, randomised, double-masked, placebo-controlled superiority trial was conducted at a single university centre. Adolescents (12–18 years) with progressive myopia were assigned to 0.01% atropine or placebo and followed for 18 months. Axial length was measured using swept-source optical biometry (IOLMaster 700) at baseline, 6, 12, and 18 months. Eye-level longitudinal mixed-effects modelling with baseline adjustment assessed treatment effects. Supportive measures included refraction, safety monitoring, and adherence checks. The trial was prospectively registered on the Clinical Trials Registry–India (CTRI ID: REF/2023/04/102943). Findings: At 18 months, the mean change in axial-length was +0.21 0.10 mm in atropine group versus +0.40 0.12 mm in placebo, giving adjusted between-group difference of -0.19 mm (p < 0.05). The differences became apparent in Month 6 and lasted up to Month 18. The paralleled axial-length results change to those of the spherical-equivalent refraction. Adherence was 93-94% and adverse events were mild (transient photophobia and near blur) with no discontinuations. Novelty: To date, fewer than five randomised, placebo-controlled trials worldwide have specifically evaluated low-dose atropine in adolescents, and only a subset employed axial length as the primary outcome. This study adds quantitative evidence that nightly 0.01% atropine provides structural protection against axial elongation with high tolerability, supporting its use as a first-line pharmacologic option in adolescent myopia control. Keywords: Myopia Control, Axial Length, Atropine 0.01%, Mixed-Effects Model, Randomised Controlled Trial