To investigate the effect of age at treatment and other factors on the treatment response to atropine in the Low-concentration Atropine for Myopia Progression (LAMP) study.
Secondary analysis from a randomized trial.
350 children, aged 4 to 12 years, randomization stratified by age and gender, originally assigned to receive 0.05%, 0.025%, 0.01% atropine, or placebo once daily in both eyes who completed 2 years of the LAMP study were included in this study. In the second year, the placebo group was switched to 0.05% atropine group.
Potential predictive factors for treatment response, that is, change in spherical equivalent (SE) and axial length (AL) over two years, were evaluated by generalized estimating equations in each of treatment group separately. The factors evaluated included age at treatment, gender, baseline refraction, parental myopia, time outdoors, diopter hours of near work, and treatment compliance. Estimated mean values and 95% CIs of change in SE and AL over two years were also generated.
MAIN OUTCOME MEASURES
Factors associated with SE change and AL change over two years were the primary outcome measures. The associated factors during the first year were secondary outcome measures.
In 0.05%, 0.025%, and 0.01% atropine group, younger age was the only factor associated with SE progression (coefficient=0.14, 0.15, and 0.20, respectively) and AL elongation (coefficient=-0.10, -0.11, and -0.12, respectively) over two years; the younger age, the poorer response. At each year of age from 4 to 12 across the treatment groups, higher-concentration atropine showed a better treatment response, following a concentration-dependent effect (P-trend for each age group <0.05). In addition, the mean SE progression in 6-years-old children in 0.05% atropine (-0.90D, 95%CI: -0.99, -0.82) was similar to that of 8-years-old in 0.025% atropine (-0.89D, 95%CI: -0.94, -0.83), and 10-years-old in 0.01% atropine (-0.92D, 95%CI: -0.99, -0.85). All concentrations were well tolerated at all age groups.
Younger age is associated with poor treatment outcomes to low-concentration atropine at 0.05%, 0.025%, and 0.01%. Among atropine concentrations studied, younger children required the highest 0.05% concentration to achieve similar reduction in myopic progression as older children on lower concentrations.