Comparison of microvascular parameters and diagnostic ability of optical coherence tomography angiography between eyes with primary angle closure glaucoma and primary open angle glaucoma

BackgroundTo investigate and compare the peripapillary and macular microvascular parameters between eyes with primary angle closure glaucoma (PACG) and primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCTA).MethodsSeventy-nine eyes of 43 patients with primary angle closure glaucoma (PACG), 78 eyes of 43 patients with primary open-angle glaucoma (POAG), 64 eyes of 35 patients with primary angle closure (PAC), and 73 eyes of 40 control subjects underwent imaging with OCTA. Perfusion density (PD) and vessel density (VD) for the macular area, and PD and flux index (FI) for the peripapillary area were calculated automatically. The area under receiver operator characteristic curves (AUC) were constructed to distinguish PACG and POAG eyes from healthy control eyes.ResultsThe peripapillary FI in all quadrants and PD and VD of the macular outer circle in superior and inferior quadrants were significantly lower in PACG and POAG eyes than in control eyes. The peripapillary FI in the inferior quadrant was significantly lower in the POAG group than in the PACG group (0.348 ± 0.06 vs. 0.369 ± 0.06, p = 0.04). The remaining OCTA parameters in the peripapillary and macular area did not show a significant difference between the POAG and PACG groups. Eyes with PAC presented significantly lower PD and VD than healthy control eyes at the superior and inferior quadrant of the macular outer circle, while retinal nerve fiber layer and ganglion cell inner complex thickness were not significantly different from than control eyes. The best diagnostic parameter was peripapillary FI in both PACG (AUC: 0.922) and POAG (AUC: 0.938) eyes.ConclusionsWe found significantly lower peripapillary FI in the inferior quadrant in POAG eyes compared to the PACG eyes, which may indicate the different underlying pathogenesis between POAG and PACG. The PAC eyes had lower macular PD and VD than normal eyes. This suggests that retinal vascular impairment may develop earlier than structural damage in PAC eyes.