Baseline factors associated with myopia progression and axial elongation over 30 months in children 5 to 12 years of age

PURPOSE This study aimed to identify baseline factors associated with greater myopia progression and axial elongation in children with myopia. METHODS This study performed a post hoc analysis of data from a 30-month randomized trial of atropine 0.01% versus placebo in children 5 to <13 years old with baseline spherical equivalent refractive error (SER) of −1.00 to −6.00 D, astigmatism of ≤1.50 D, and anisometropia of <1.00 D SER. Data from atropine 0.01% and placebo groups were pooled given outcomes were similar. Baseline factors of age, SER, axial length, race, sex, parental myopia, and iris color were evaluated for association with changes in SER and with changes in axial length at 30 months (24 months on treatment and then 6 months off) using backward model selection. RESULTS Among 187 randomized participants, 175 (94%) completed 30 months of follow-up. The mean change in SER was greater among younger children (−0.19 D per 1 year younger; 95% confidence interval [CI], −0.25 to −0.14 D; p<0.001) and children with higher myopia (−0.14 D per 1 D more myopia at baseline; 95% CI, −0.23 to −0.05 D; p=0.002). The mean change in axial length was also greater among younger children (0.13 mm per 1 year younger; 95% CI, 0.10 to 0.15 mm; p<0.001) and children with higher baseline myopia (0.04 mm per 1 D more myopia; 95% CI, 0.002 to 0.08; p=0.04). CONCLUSIONS Younger children with higher myopia had greater myopic progression and axial elongation over 30 months than older children with lower myopia. Developing effective treatments to slow the faster myopic progression in younger children should be a target of further research.