Oral administration of caffeine metabolite 7-methylxanthine is associated with slowed myopia progression in Danish children

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 (0-1200 mg 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 1000 mg 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 0.84 mm over 6 years when taking a daily dose of 1000 mg of 7-MX, compared with 1.01 mm 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.