This is a double-blind, randomised, placebo-controlled trial evaluating the effects of low-concentration atropine (0.05%, 0.025%, 0.01%) on ocular biometrics of myopic children. The aim is to determine what aspect of ocular biometrics low-concentration atropine influenced in reducing the progression of myopia. The participants were recruited from the Low-Concentration Atropine for Myopia Progression (LAMP) study, which included 438 children aged 4-12 years with myopic refraction of at least -1.0D in both eyes and astigmatism of less than 2.5D. Ocular biometric measurements of axial length, cycloplegic spherical equivalent, corneal curvature, astigmatism, lens power and anterior chamber depth were measured following at least two cycles of atropine eye drop administrations. Measurements were obtained for both eyes at the initial visit, and after two-weeks and four-months for one year. Results included 383 participants (87%) that completed the first-year follow-up. Low-concentrations of atropine were found to have no clinical effect on corneal or lens power, remaining stable across all atropine concentrations. Axial length changes had a concentration-dependent response of 0.20 ±0.25mm, 0.29 ±0.20mm, 0.36 ±0.29mm, and 0.41 ±0.22mm in the 0.05% atropine, 0.025% atropine, 0.01% atropine, and placebo groups, respectively (P<0.001). This study demonstrates that the anti-myopic effects of low-concentration atropine is caused by a reduction in axial length elongation, most notable in the 0.05% atropine group. This study is limited by a relatively short follow-up period of one year. Further long-term evaluations particularly after cessation of treatment will be of interest.