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Purpose Myopia is associated with an increased risk of permanent vision loss. The caffeine metabolite 7-methylxanthine (7-MX), licensed in Denmark since 2009 as a treatment to reduce the rate of childhood myopia progression, is the only orally administered therapy available. The purpose of the current study was to assess the rate of myopia progression in children taking 7-MX. Methods Longitudinal cycloplegic refraction and axial length data for 711 myopic children from Denmark treated with varying doses of oral 7-MX (0–1200mg per day) were analysed using linear mixed models. Results The median age at baseline was 11.1 years (range 7.0 –15.0 years). Children were followed for an average of 3.6 years (range 0.9–9.1 years) and the average myopia progression was 1.34 dioptres (D) (range −6.50 to +0.75 D). Treatment with 7-MX was associated with a reduced rate of myopia progression (p<0.001) and axial elongation (p<0.002). Modelling suggested that, on average, an 11-year-old child taking 1000mg 7-MX daily would develop −1.43 D of myopia over the next 6 years, compared with −2.27 D if untreated. Axial length in this child would increase by 0.84mm over 6 years when taking a daily dose of 1000mg of 7-MX, compared with 1.01mm if untreated. No adverse effects of 7-MX therapy were reported. Conclusions Oral intake of 7-MX was associated with reduced myopia progression and reduced axial elongation in this sample of myopic children from Denmark. Randomised controlled trials are needed to determine whether the association is causal. [ABSTRACT FROM AUTHOR]