there is distinct pathogenesis between primary open-angle glaucoma (poAG) and primary angleclosure glaucoma (pAcG). Although elevated intraocular pressure (iop) is the major risk factor for glaucoma, non-IOP risk factors such as vascular abnormalities and lower systolic/diastolic perfusion pressure may play a role in the pathogenic process. this study aimed to compare the vessel density (VD) in the optic disc and macula using optical coherence tomography angiography (octA) between poAG and PACG eyes. Thirty-two POAG eyes, 30 PACG eyes, and 39 control eyes were included. All the optic disc VD parameters except the inside disc VD were significantly lower in glaucomatous eyes than in control eyes. Compared with PACG eyes, only the inferior temporal peripapillary VD was significantly lower in POAG eyes. The parafoveal VD was significantly lower in each quadrant in glaucomatous eyes than in control eyes. The central macular and parafoveal VD did not differ between POAG and PACG eyes. In conclusion, the inferior temporal peripapillary VD was significantly reduced in POAG eyes compared with PACG eyes, while PACG eyes showed a more evenly distributed reduction in the peripapillary VD. The distinct patterns of VD change may be associated with the different pathogenesis between poAG and pAcG. Glaucoma is an optic neuropathy characterised by progressive loss of retinal ganglion cells and their axons accompanied by corresponding visual field (VF) defects. Primary glaucoma is classified according to the anatomy of the anterior chamber angle into primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). Elevated intraocular pressure (IOP) is the major risk factor for glaucoma. In PACG, elevated IOP secondary to angle closure is considered the primary mechanism. On the other hand, other non-IOP risk factors such as vascular abnormalities and lower systolic/diastolic perfusion pressure have been proposed in POAG 1-4. The characteristics of the optic disc are also different between POAG and PACG eyes. There may be enlarged cupping and/or optic disc rim notching in POAG eyes, whereas pallor of the optic disc either from an acute attack of angle closure or in the chronic clinical course may be observed in PACG eyes 5,6. All these findings indicate the distinct pathogenesis between POAG and PACG and reflect the feature of microvascular damage. Optical coherence tomography angiography (OCTA) is a reliable technique to perform in vivo imaging of the optic nerve head (ONH) and retinal microcirculation 7-11. Previous studies have reported reduced vessel density (VD) in the ONH, peripapillary area, and macula in glaucomatous eyes 12-17. Most of the studies investigated POAG eyes and had limited analyses for the microcirculation in PACG eyes 18-21. The diagnostic ability of VD as well as the relationship of peripapillary VD with VF and/or retinal nerve fibre layer (RNFL) thickness in POAG and PACG have been reported 18-28. To date, no reports have compared the pattern of regional VD change in the optic disc or macula b...