Three-Year Clinical Trial of Low-concentration Atropine for Myopia Progression (LAMP) Study: Continued Versus Washout. Phase 3 Report

PURPOSE (1) To compare the efficacy of continued and stopping treatment for 0.05%, 0.025%, and 0.01% atropine during the third year. (2) To evaluate the efficacy of continued treatment over 3 years. (3) To investigate the rebound phenomenon and its determinants after cessation of treatment. DESIGN A randomized, double-masked extended trial. PARTICIPANTS A total of 350 of 438 children aged 4 to 12 years originally recruited into the Low-Concentration Atropine for Myopia Progression (LAMP) study. METHODS At the beginning of the third year, children in each group were randomized at a 1:1 ratio to continued treatment and washout subgroups. Cycloplegic spherical equivalent (SE) refraction and axial length (AL) were measured at 4-month intervals. MAIN OUTCOME MEASURES Changes in SE and AL between groups. RESULTS A total of 326 children completed 3 years of follow-up. During the third year, SE progression and AL elongation were faster in the washout subgroups than in the continued treatment groups across all concentrations: -0.68 ± 0.49 diopters (D) versus -0.28 ± 0.42 D (P < 0.001) and 0.33 ± 0.17 mm versus 0.17 ± 0.14 mm (P < 0.001) for the 0.05%; -0.57 ± 0.38 D versus -0.35 ± 0.37 D (P = 0.004) and 0.29 ± 0.14 mm versus 0.20 ± 0.15 mm (P = 0.001) for the 0.025%; -0.56 ± 0.40 D versus -0.38 ± 0.49 D (P = 0.04) and 0.29 ± 0.15 mm versus 0.24 ± 0.18 mm (P = 0.13) for the 0.01%. Over the 3-year period, SE progressions were -0.73 ± 1.04 D, -1.31 ± 0.92 D, and -1.60 ± 1.32 D (P = 0.001) for the 0.05%, 0.025%, and 0.01% groups in the continued treatment subgroups, respectively, and -1.15 ± 1.13 D, -1.47 ± 0.77 D, and -1.81 ± 1.10 D (P = 0.03), respectively, in the washout subgroup. The respective AL elongations were 0.50 ± 0.40 mm, 0.74 ± 0.41 mm, and 0.89 ± 0.53 mm (P < 0.001) for the continued treatment subgroups and 0.70 ± 0.47 mm, 0.82 ± 0.37 mm, and 0.98 ± 0.48 mm (P = 0.04) for the washout subgroup. The rebound SE progressions during washout were concentration dependent, but their differences were clinically small (P = 0.15). Older age and lower concentration were associated with smaller rebound effects in both SE progression (P < 0.001) and AL elongation (P < 0.001). CONCLUSIONS During the third year, continued atropine treatment achieved a better effect across all concentrations compared with the washout regimen. 0.05% atropine remained the optimal concentration over 3 years in Chinese children. The differences in rebound effects were clinically small across all 3 studied atropine concentrations. Stopping treatment at an older age and lower concentration are associated with a smaller rebound.