Over a two-year period, researchers found that the efficacy of 0.05% atropine was double that of a 0.01% formulation, making it the optimal concentration in slowing myopia progression.

This randomized, double-masked trial extended the Low-concentration Atropine for Myopia Progression (LAMP) study, evaluating 383 children aged four to 12 years old with at least -1.0D of myopia who were randomized to receive atropine 0.05%, 0.025% or 0.01% once daily in both eyes.

The team measured cycloplegic refraction, axial length (AL), accommodation amplitude, photopic and mesopic pupil diameter and best-corrected visual acuity in four-month intervals to pinpoint changes in spherical equivalent (SE) and AL within and between groups.

The investigators discovered that the mean SE progressions were 0.55±0.86D, 0.85±0.73D and 1.12±0.85D with mean AL changes of 0.39±0.35mm, 0.50±0.33mm and 0.59±0.38mm in the 0.05%, 0.025% and 0.01% atropine groups, respectively. Compared with the first year, they noted that the second-year efficacy of 0.05% and 0.025% remained similar but mildly improved in the 0.01% atropine group. For those who were in the placebo group in the first phase of the LAMP study and then switched to 0.05% atropine, myopia progression was significantly reduced (SE changes of 0.82D in the first year and 0.18D in the second; AL elongations of 0.43mm in the first year and 0.15mm in the second).

They added that loss in accommodation and change in pupil size were similar to the first-year results in all concentrations and were well tolerated, with visual acuity and vision-related quality of life remaining unaffected.