We carefully read the study by Loh and associates and found it very interesting. It describes myopic progression despite atropine treatment.

In this study, 200 children with low to moderate myopia were treated in one randomly assigned eye with atropine 1% during 2 years. The results show that 12.1% of children progressed despite atropine 1% treatment. These myopic progressor patients were younger, had higher myopia at baseline, and had greater progression in the untreated eye.

In the methods section, the authors stated that axial length (AL) was measured by A-scan ultrasonography. However, we did not find, in the manuscript, any data on AL evolution, either in the results section or in the discussion. This surprised us and we think that such results, even briefly described, could be interesting.

As a matter of fact, refraction value may be used to define myopia and high myopia, such as in genetic studies. But, to date, it is now widely admitted that AL is the main determinant of refractive error and that it can be considered as an endophenotype of myopia. The evolution in such definition is the consequence of the wide variety of myopia definition. It is also the consequence of the evolution of knowledge concerning the importance of sclera remodeling and, thus, of the vitreous chamber length in AL determinism.

Moreover, atropine, when used to prevent myopia progression, would have an action on sclera remodeling via muscarinic receptors and, thus, on AL.

To conclude, we think that the quality of this study would be improved by adding AL results.