We have read and reviewed the article entitled “Vascular density in retina and choriocapillaris as measured by optical coherence tomography angiography,” by Wang and associates, with great interest. The authors investigated the density of the superficial retinal small vessel, superficial retinal capillary, and deep retinal capillary networks and choriocapillaris, as well as the size of the foveal avascular zone in the superficial retinal layer of normal eyes, by split-spectrum amplitude-decorrelation angiography with optical coherence tomography. Subfoveal choroidal thickness (CT) was measured with optical coherence tomography (OCT). The authors found that the density of the macular vascular networks decreased along with increasing age, and this decrease was independent of axial length and subfoveal CT in the healthy individuals. We express our gratitude to Wang and associates for their comprehensive research. However, we would like to ask some questions to the authors, since those factors might have significantly affected the results of the study.

First, the authors indicated that the number of participants included in this study was 105, 66 of them were female, and their ages ranged between 17 and 64 years. It has been demonstrated in the literature that pregnancy and menstrual cycle may significantly affect CT size. Ulaş and associates analyzed 23 female subjects and showed that there was a significant decrease in CT during the mid-luteal phase, and a decrease of 6.4% was observed between early follicular and mid-luteal phases. On the other hand, a significant increase in CT was observed during the second trimester of pregnancy. Therefore, we would like to ask the authors whether they considered the menstrual cycle and pregnancy status of the female participants.

Second, when the age distribution of the participants is considered, systemic diseases that may significantly affect CT, such as diabetes, hypertension, hyperlipidemia, metabolic and rheumatologic disorders, and inflammatory diseases, should be indicated in the study. Moreover, we anticipate that the medications used for those diseases may also affect the outcomes of the study.

Third, as Wang and associates have already indicated in the paper, CT demonstrates a significant diurnal variation. Usui and associates investigated subfoveal CT and demonstrated that subfoveal CT was the thinnest at 6 PM (271.9 ± 103.5 μm) and thickest at 3 AM (290.8 ± 110.8 μm). In that study, Usui and associates showed that diurnal variation of CT might be up to 65 μm (ranging between 8 and 65 μm). Another study, by Lee and associates, reported that the mean diurnal variation of CT was 20.32 ± 10.40 μm (ranging between 4 and 60 μm).

Fourth, the factors that have been shown to affect the CT in the literature, such as smoking, consumption of caffeinated food or beverages, and body mass index, should be indicated in the paper.

In conclusion, we suggest that factors that affect CT may also affect the macular vascular network with similar mechanisms, and significantly change the results of the study.