Five-Year Clinical Trial of Low-concentration Atropine for Myopia Progression (LAMP) Study: Phase 4 Report.

PURPOSE: To evaluate (1) the long-term efficacy of low-concentration atropine over 5 years, (2) the proportion of children requiring retreatment and associated factors (3) the efficacy of pro re nata (PRN) retreatment using 0.05% atropine from year 3 to 5.

DESIGN: A randomized, double-masked extended trial.

METHODS: Children aged 4-12 years originally from the Low-Concentration Atropine for Myopia Progression study were followed up for 5 years. During the third year, children in each group originally on 0.05%, 0.025%, and 0.01% atropine were randomized to continued treatment and treatment cessation. During years 4 and 5, all continued treatment subgroups were switched to 0.05% atropine for continued treatment, while all treatment cessation subgroups followed a PRN retreatment protocol to resume 0.05% atropine for children with myopic progressions of 0.5D or more over one year. Generalized estimating equations were used to compare the changes in spherical equivalent (SE) progression and axial length (AL) elongation among groups.

OUTCOMES MEASURES: (1) Changes in SE and AL over 5 years in different groups over 5 years; (2) Proportion of children who needed retreatment; (3) Changes in SE and AL in continued treatment and PRN retreatment groups from years 3 to 5.

RESULTS: 269 (82.5%) of 326 children from the third year completed 5 years of follow-up. Over 5 years, the cumulative mean SE progressions were -1.34±1.40D, -1.97±1.03D, and -2.34±1.71D for the continued treatment groups with initial 0.05%, 0.025%, and 0.01% atropine respectively (P=0.02). Similar trends were observed in AL elongation (P=0.01). Among the PRN retreatment group, 87.9%(94/107) of children needed retreatment. The proportion of retreatment across all studied concentrations is similar (P=0.76). The SE progressions for continued treatment and PRN retreatment groups from years 3 to 5 were - 0.97D±0.82D, and -1.00±0.74D (P=0.55), and the AL elongations were 0.51±0.34mm, and 0.49±0.32mm (P=0.84), respectively.

CONCLUSIONS: Over 5 years, the continued 0.05% atropine treatment demonstrated good efficacy for myopia control. The majority of children needed to restart treatment after atropine cessation at year 3. Restarted treatment with 0.05% atropine achieved similar efficacy as continued treatment. Children should be considered for retreatment if myopia progresses after treatment cessation.