To the Editor:I read the article by Li et al.1Li F.F. Zhang Y. Zhang X. et al.Age effect on treatment responses to 0.05%, 0.025%, and 0.01% atropine: Low-concentration Atropine for Myopia Progression (LAMP) Study. The study is a secondary analysis from the Low-concentration Atropine for Myopia Progression (LAMP) randomized trial and mainly aimed to investigate the effect of age on the treatment response to atropine. The research included children aged 4 to 12 years old who completed 2 years of the LAMP study. The estimated mean of spherical equivalent (SE) progression and axial length (AL) elongation over 2 years were calculated by generalized estimating equation and compared in atropine treatment groups. The research was well-performed and demonstrated that the treatment responses to low-concentration atropine were poorer in younger children. However, after carefully reviewing the article and recalculating the treatment responses with the provided data, I found that the author did not consider the physiologic myopia progression and AL elongation at different ages during the analysis that potentially achieved a problematic conclusion.The author calculated and showed the SE change and AL elongation in different ages of each group. The result seems perfect and manifested that the younger the age, the greater the SE progression and AL elongation. The effect of age was similar in different concentration atropine groups and identical over 1- and 2-year observation periods. However, the physiologic AL elongation and SE progression were greater in younger myopic children,2Jones L.A. Mitchell G.L. Mutti D.O. et al.Comparison of ocular component growth curves among refractive error groups in children.,3Saw S.M. Nieto F.J. Katz J. et al.Factors related to the progression of myopia in Singaporean children. and the placebo group results in the article also confirm it.1Li F.F. Zhang Y. Zhang X. et al.Age effect on treatment responses to 0.05%, 0.025%, and 0.01% atropine: Low-concentration Atropine for Myopia Progression (LAMP) Study. Thus, the poorer treatment outcome in younger children might be due to their faster physiologic myopia progression, and the actual effect of age on treatment benefit might be contrary to the treatment outcome. Adjusting the physiologic SE progression and AL elongation in the analysis could probably solve the problem and better demonstrate the effect of age on the treatment response.According to the data provided in the article, I recalculated the treatment response in different ages adjusting the physiologic SE progression and AL elongation. The SE changes and AL elongation in the placebo group were treated as the physiologic changes in different ages (Tables S4 and S5 in the Li et al article1Li F.F. Zhang Y. Zhang X. et al.Age effect on treatment responses to 0.05%, 0.025%, and 0.01% atropine: Low-concentration Atropine for Myopia Progression (LAMP) Study.). Owing to the switchover of the placebo group in the second year, there is a lack of 2-year physiologic changes. The 2-year change in SE and AL of a certain age (N) in the placebo group were assumed as the 1-year change from age N plus data from age N + 1 in the placebo group. The differences of the estimated mean between the treatment and placebo group changes at different ages were calculated and demonstrated in Table 1. The analysis demonstrated that the treatment response of SE and AL was similar at different ages in the 3 treatment groups over the first year. Analyzing 2-year results, the treatment response of SE and AL was greater in younger children, and the results were similar in the 3 treatment groups. Thus, the younger the age, the treatment response was better, although the treatment outcome seems poorer.

Table 1Adjusted Atropine Treatment Response on SE and AL over 1 and 2 Years in Different Ages of Each Treatment Group

AL = axial length; NA = not available; SE = spherical equivalent.

The 1-year and 2-year results were calculated as the difference between the atropine group and placebo group at the same age. The 2-year change results of a certain age (N) in the placebo group were calculated as the 1-year change from age N plus N + 1 in the placebo group.

Age is an important influential factor for myopia progression. The research on the investigation of treatment effect for myopic children should consider the physiologic AL elongation and myopia progression.

ReferencesLi F.F. Zhang Y. Zhang X. et al.

Age effect on treatment responses to 0.05%, 0.025%, and 0.01% atropine: Low-concentration Atropine for Myopia Progression (LAMP) Study.

Ophthalmology. ()Jones L.A. Mitchell G.L. Mutti D.O. et al.

Comparison of ocular component growth curves among refractive error groups in children.

Invest Ophthalmol Vis Sci. 46: 2317-2327Saw S.M. Nieto F.J. Katz J. et al.

Factors related to the progression of myopia in Singaporean children.

Optom Vis Sci. 77: 549-554Article InfoPublication History

Published online: June 17, 2021

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The authors have no proprietary or commercial interest in any materials discussed in this article.

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DOI: https://doi.org/10.1016/j.ophtha.2021.05.024

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© 2021 by the American Academy of Ophthalmology

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