We read with great interest about the recent article by Akagi and associates exploring the change and relationship of peripapillary retina microcirculation, hemifield visual field (VF) defects, and the thickness of the retinal nerve fiber layer (RNFL). They found that microvascular reduction was associated with VF defects in the peripapillary retina and partially at the optic disc. However, we have concern about several questions. First, this study includes 60 eyes with primary open-angle glaucoma (POAG) and 26 eyes with high myopia. Among the 60 eyes, 41 eyes had superior and 19 eyes had inferior hemifield VF defects. However, in Table 2, the number of POAG eyes without high myopia totals 44, including 23 superior hemifield VF defect and 11 inferior hemifield VF defects; will the authors explain this inconformity?

Second, this study demonstrated the change of microvascular density in the peripapillary superficial retina of POAG patients with hemifield VF defects and also the thickness of RNFL; however, how the change of retinal microvascular density and the thickness of RNFL exactly located the area of visual defect, not just the peripapillary area, remained unknown.

Finally, this study is a cross-sectional observation study, which could not tell the exact cause-and-effect relationship between visual defect and retinal microcirculation (structure vs function in glaucoma), whereas in the recent report from HannaMaria Öhnell and associates, in the eyes with manifest glaucoma, progression in the visual field was detected first more than 4 times as often as progression in the optic disc ; it will be more significant to have a prospective and longitudinal trial to explore which one will be more sensitive to detect glaucoma and the progression of glaucoma. This will help clarify the role of ocular circulation regarding its involvement in the pathogenesis of glaucoma.