We have read the interesting article entitled “Choroidal and retinal thickness in children with different refractive status measured by swept-source optical coherence tomography,” by Jin and associates. The authors investigated the choroidal thickness (CT) and retinal thickness in myopic, emmetropic, and hyperopic children with swept-source optical coherence tomography (OCT). They found that myopic children had significantly thinner choroids in all regions, and hyperopic children had thicker choroids in most of the regions when compared with emmetropic eyes. Additionally, Jin and associates demonstrated that CT, but not retinal thickness, was closely correlated with axial length (AL) and refractive diopters in children. We express our gratitude to the authors for this valuable study, and would like to ask about some points that may affect CT measurements.

The CT is affected by various local and systemic states. It has been indicated in the literature that age, sex, diurnal variation, systemic and local diseases, medications, AL, intraocular pressure, refractive errors, and numerous other factors may affect CT. Although Jin and associates addressed various factors affecting CT, we would like to address some important points to the authors.

First, it was indicated in the paper that the number of children included this study was 276, their age range was 7-13 years, and 131 of those children were female. The effect of menstrual cycle on CT is well known. Previously, Ulaş and associates demonstrated that there was a significant decrease in CT during the mid-luteal phase, and a decrease up to 6.4% was observed between early follicular and mid-luteal phases. Therefore, we are curious whether menstrual cycles of female participants were considered in the study.

Second, we would like to ask the authors whether physical exercise status and consumption of caffeinated/decaffeinated food or beverages were considered before OCT measurements. In a recent study, Dervişoğulları and associates investigated the effects of caffeine on CT and demonstrated that a significant decrease in CT was observed for at least 4 hours after consuming 200 mg of caffeine. In addition, Sayin and associates demonstrated that CT thickness increased for at least 5 minutes after dynamic physical exercise.