Quantification of Retinal Microvascular Density Using Optic Coherence Tomography Angiography in Primary Angle Closure Disease

Purpose: To evaluate the microvascular density of the peripapillary and parafoveal areas of the eyes with primary angle closure disease (PACD) using optical coherence tomography angiography (OCTA). Materials and methods: An observational study was conducted with 76 PACD patients (29 eyes with primary angle closure suspect, 22 eyes with primary angle closure [PAC], and 25 eyes with primary angle closure glaucoma [PACG]) and 27 control eyes. OCTA was performed for all subjects to acquire a 4.5 x 4.5 mm scanning area centered on the optic discs and a 3 x 3 mm parafoveal cubes. Peripapillary and parafoveal vessel density (VD) were compared between these four groups, and the relationship between VD values and structural and functional changes was evaluated. Results: Among all four groups, the peripapillary VD of the PACG eyes was the lowest in all six sections (all P < .01), while the parafoveal VD was lower than that of the normal group only in the average, superior, and inferior areas (all P < .05). The PAC group had lower peripapillary VD than the normal group (62.6[55.2-67.4] vs. 66.7[54.7-69.3], P = .01), while their retinal nerve fiber layer (RNFL) and ganglion cell complex thickness were not significantly different than those of the control group (all P > .05). In addition, the stages of PACD, visual field mean deviation, and RNFL thickness were shown to be predictors of the peripapillary VD in the multiple linear regression analysis. Conclusions: The PAC eyes had lower peripapillary VD than normal eyes when their RNFL and GCC thickness did not differ. This suggests that a reduction in retinal VD may occur before structural loss in PAC eyes. Retinal VD measurement may be a useful tool for the assessment of PACD.