Effectiveness of a split-dose, twice-daily low-dose atropine monocular treatment in children with anisometropia: a retrospective study

Purpose: To evaluate the efficacy of a split-dose, twice-daily atropine treatment with 0.05% atropine administered at bedtime and 0.025% atropine administered in the late afternoon in reducing interocular differences in spherical equivalent (SE) and axial length (AL) in children with myopic or mixed anisometropia. Methods: Medical records of 39 children with anisometropia who received 0.05% atropine at bedtime and 0.025% atropine in the late afternoon for the eye with longer AL were retrospectively reviewed. Participants were divided into younger (5–7 years) and older (8–9 years) groups according to age at treatment initiation, or into myopic and mixed anisometropia groups according to anisometropia type. Ophthalmologic examinations were performed every six months over an average follow-up period of 4.2 years, with analyses focusing on changes in SE, AL, and interocular differences. Outcomes were compared based on anisometropia type and age at treatment initiation. Results: Interocular SE difference significantly decreased from 3.15 to 1.53 D (mean change = 1.62 D, Cohen’s d = 1.98, 95% CI = 1.36–1.88, p < 0.001), and interocular AL difference decreased from 1.07 mm to 0.54 mm over a 4.2 year period (mean change = 0.53 mm, Cohen’s d = 1.66, 95% CI = 0.43–0.63, p < 0.001). Notably, 74.4% of participants reduced their SE difference to < 2.0 D, with 28.2% achieving a reduction to 1.0 D or less. Both myopic and mixed anisometropia groups demonstrated significant reductions in interocular differences of SE and AL, with no significant differences in annual changes of SE or AL. The younger group showed a more significant reduction in AL in the treated eye than the older group (p = 0.035). Near-vision impairment during near-work tasks was not observed. Conclusion: A split-dose, twice-daily atropine regimen—comprising 0.05% at bedtime and 0.025% in the late afternoon—may be effective in reducing interocular differences in SE and AL in children with anisometropia, with good tolerability. Early initiation of treatment may be associated with more favorable outcomes in AL control. Further prospective studies are warranted to confirm these findings and evaluate long-term efficacy.