To the Editor:

We are very glad to see that Professor Dr. Dahlmann-Noor commented on our published paper “Measuring changes in Schlemm’s canal (SC) and trabecular meshwork (TM) in different accommodation states in myopia children” [1]. Although they published two outstanding studies [2, 3] earlier than us, we thought it is not controversial as we stated that our study is the first in vivo study on the effect of accommodation on TM and SC structure in myopia patients. In their paper, Professor Dr. Dahlmann-Noor analyzed the effect of accommodation on the SC and TM in children with healthy eyes [2], but the detail refractive status was not mentioned and stratified analysis based on refractive status was not done. We thank Professor Dr. Dahlmann-Noor for providing detailed data on participants with myopia to readers in their comments. It is known that refractive status is closely related to accommodative ability. For example, a thicker ciliary body has been reported in myopic children, which may contribute to accommodative inaccuracies including accommodative lag [4, 5]. Further, the size of SC and TM could be different between myopia and hypermetropia [6]. We studied myopic eyes and they studied children with mixed refractive status. Certainly, we are very glad to see that those changes are not limited to children with myopia based on their findings. In addition, the interventions are different in the two studies: ciliary muscle paralysis, accommodation relaxation, and −6 D accommodative stimulation were used in our study, while −2.5 D (“relaxed accommodation”) and −15 D accommodation stimulation status were done in theirs.

They demonstrated a clear image of ciliary muscle thickness at 1 mm (CM1) from the scleral spur. In fact, we could achieve same qualified images of CM1 in many subjects (Fig. 1a, b) but not all of them. The reason could be differences in ciliary muscle thickness, vascular density, and pigments contexture, which result in different tissue penetrability of scanning signal. Even without CM1 data, we thought that our conclusion is reasonable, for changes of CM2, CM3, central lens thickness, and anterior chamber depth representing different accommodation states well, which is in line with other studies [7, 8].

Fig. 1: The OCT image of ocular anterior segment.
figure 1

a One OCT image from 10 years old. b One OCT image from 8 years old.

Full size image

They also did an excellent work to explore the effect of childhood lensectomy on cross-sectional area of SC with and without accommodative effort and they concluded that accommodative efforts do not increase SC dimensions [3]. We believe that their speculation is not in contradiction with our explanation. We thought that under stimulation stress, SC opening results from the sclera spur or the cribriform plexus connected to the endothelial cells of SC in TM structure, which are pulled by ciliary muscle when it contracts. TM anatomically locates between SC and ciliary muscle, and functionally mediates ciliary muscle’s pulling force on SC when ciliary muscle contracts. Thus, either ciliary muscles paralyzed with tropicamide or TM damaged after lensectomy, could have same effect on SC when giving accommodation stimuli.