Optic Disc and Macular Vessel Density Measured by Optical Coherence Tomography Angiography in Open-Angle and Angle-Closure Glaucoma

Abstract

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...

Comparison of optical coherence tomography angiography metrics in primary angle-closure glaucoma and normal-tension glaucoma

“…The findings might reflect a more specific and early reduction of microvascular perfusion at the peripapilliary region of NTG eyes at early stage glaucoma. Such a difference was not observed in other studies that compared patients with PACG and POAG (involved both NTG and HTG) 35 , 36 .…”

Analysis of structural and vascular changes of the optic nerve head and macula in different stages of primary open angle glaucoma

“…[21][22][23] Some literature data presents that all the optic disc VD parameters except the inside disc VD were significantly lower in glaucomatous eyes than in control eyes. 24 Other results indicate the VCD in the radial papillary capillaries layer and in the nerve head layer of glaucomatous eyes was significantly lower than in age-matched control eyes. 1 The same authors presented results that VCD in all peripapillary segments was higher than in nerve head layer, similar to our findings.…”

Comparison of Optical Coherence Tomography Angiography Metrics in Primary Angle-Closure Glaucoma and Normal-Tension Glaucoma

“…Such a difference was not observed in other studies that compared patients with PACG and POAG (involved both NTG and HTG). 34,35 Given the similar disease severity and the number of medications used, the difference in cpVD between NTG and PACG eyes could be related to the different pathogenic mechanisms of the two glaucoma subtypes. For NTG at the early stage, the impairment of vascular autoregulation -postulated to be an important risk factor for disease progression in NTG 5,6,[36][37][38] -could lead to reduced blood ow but has yet to cause dysfunction, death, or atrophy of the RGC, as well as the consequential RNFL thinning.…”