Peripapillary vessel density measurement of quadrant and clock-hour sectors in primary angle closure glaucoma using optical coherence tomography angiography

Abstract

Background: The purpose of this study was to investigate diagnostic ability of peripapillary vessel density of primary angle closure glaucoma (PACG) eyes in quadrant and clock-hour sectors by optical coherence tomography angiography (OCTA).

Methods: This was a cross-sectional study on forty-one PACG patients (41eyes) and twenty-seven healthy subjects (27 eyes). All subjects underwent OCTA (DRI OCT Triton; Topcon Corporation, Tokyo, Japan) and peripapillary retinal nerve fiber layer (RNFL) thickness imaging with swept-source optical coherence tomography (OCT). The peripapillary vessel density of quadrant and clock-hour sectors was quantified by imageJ software. The diagnostic capability of OCTA and OCT parameters was evaluated by the areas under the receiver operating characteristics curves (AUCs). Pearson correlation analysis or Spearman correlation test was used to evaluate the correlation between vessel density parameters and related factors.

Results: Compared with the control group, the peripapillary vessel density of glaucomatous group was lower to different degrees in the four quadrants and each clock-hour sectors, and vessel density reduced most at 7 o'clock. The difference between the diagnostic ability of peripapillary vessel density and peripapillary RNFL thickness was not statistically significant, except 4 o'clock and inferior quadrant. The inferior quadrant peripapillary vessel density had the best diagnostic value (AUC0.969), followed by the 7 o'clock vessel density (AUC0.964), average vessel density (AUC0.939) and the 7 o'clock RNFL thickness (AUC0.919). The average peripapillary vessel density was correlated with average RNFL and visual field (VF) mean deviation (P < 0.001).

Conclusions: In PACG, the diagnostic ability of the peripapillary vessel density is equivalent to the peripapillary RNFL thickness. Understanding spatial characteristics of the peripapillary vessel density in PACG may be helpful for clinical diagnosis and monitoring the progress of diseases.

Keywords: Optical coherence tomography angiography; Peripapillary vessel density; Primary angle closure glaucoma.

Fig. 1

OCT-A image processing steps. A Image imported into the Image J software and noise reduction processing. B Binary image after local adaptive thresholding. C Annular region of interest centered at the optic nerve head. D Obtaining vessel density values of each quadrant and clock-hour sector

Fig. 2

Example of PACG eye with decreased infratemporal and supratemporal vessel density of optic disc. The infratemporal and supratemporal peripapillary vessel density of glaucoma decreased and the peripapillary retinal nerve fiber layer in corresponding areas atrophied. (first row) On the contrary, these areas were very high in healthy eyes. (second row) (A) Nerve Head scan of glaucoma eye and (B) Corresponding color-coded vessel density map of the Nerve Head layer (C) Vessel density value at clock-hour region of glaucoma eye (D) Peripapillary retinal nerve fiber layer thickness at clock-hour region of glaucoma eye (E) Nerve Head scan of healthy eye and (F) Corresponding color-coded vessel density map of the Nerve Head layer (G) Vessel density value at clock-hour region of healthy eye (H) Peripapillary retinal nerve fiber layer thickness at clock-hour region of healthy eye