Changes of Optic Disc and Macular Vessel Perfusion Density in Primary Angle Closure Glaucoma: A Quantitative Study Using Optical Coherence Tomography Angiograph

INTRODUCTION: This study aims to investigate the changes of retinal vascular system in primary angle closure glaucoma (PACG) and acute primary angle closure (APAC) by optical coherence tomography (OCT) angiograph (OCTA) and to evaluate the diagnostic ability of changes of vessel density (VD) in different sectors and layers of optic disc and macular area in APAC and PACG. METHODS: In this cross-sectional, observational study, 21 APAC patients (22 eyes) and 21 PACG patients (27 eyes) along with 17 healthy people were enrolled from August 2018 to March 2019. Optic disc region and macular region were imaged using swept-source OCTA system. VD of the macular region was quantified by Image J (1.52a, USA) and Matlab 2018a. The circumpapillary retinal nerve fiber layer (cpRNFL) thickness and ganglion cell complex thickness were obtained by spectral-domain OCT. RESULTS: Compared with the healthy group, the cpRNFL thickness in superior sector was thicker in the APAC group, and this area had the most diffuse microvascular dropout as well. The difference in the macular superficial capillary plexus (SCP) VD between APAC and the control group was not statistically significant. The area under the ROC curves (AUC) of the total optic disc VD in the radial peripapillary capillary (RPC) layer was higher than the AUC of the papillary VD in the optic nerve head (ONH) layer. Compared to the control group, the total optic disc VD, peripapillary VD, and each quadrant of peripapillary VD were decreased in PACG (p < 0.01). In PACG macular region, SCP VD, and deep capillary plexus (DCP) VD, parafovea VD (except temporal sectors) decreased (p < 0.01). The PACG eyes had a greater decrease percentage of VD in total ONH than total macula. The diagnostic value of the VD in the ONH layer and the RPC layer was similar. The diagnostic value of the SCP VD in the macula was greater than the DCP VD in the macula. The AUC was no significant difference between cpRNFL thickness and the total optic disc VD AUC. CONCLUSION: Elevated intraocular pressure preferentially affects vascular perfusion in the optic disc region more than the macular region in APAC and PACG. In the APAC eyes, there was a perfusion defect in the optic disc region and an increase in RNFL thickness. In this study, the OCTA vascular parameters have similar performance to the OCT structural parameters for glaucoma diagnosis in PACG.