Analysis of the optic nerve head microcirculation using OCT-A and the upstream macrocirculation using CDI in low- and high-tension glaucoma patients

Introduction: To analyze the optic nerve head (ONH) microcirculation using optical coherence tomography angiography (OCT-A) and the upstream macrocirculation using color Doppler imaging (CDI) in low-tension and high-tension glaucoma (LTG and HTG, respectively). Methods: This cross-sectional study included 67 eyes of 67 HTG patients, 55 eyes of 55 LTG patients, and 42 eyes of 42 healthy controls. We recorded the complete ophthalmological examination, visual fields, retinal nerve fiber layer (RNFL) thickness, ONH vessel density (VD) measured using OCT-A, peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) measured using CDI. SPSS software was used for data analysis. Data are presented as mean ± standard deviation or median (interquartile range) and compared using t-test or Mann-Whitney U test, as appropriate. Pearson chi-square test or Fisher’s exact test was used for comparisons, as appropriate. Pearson correlation analysis was used to evaluate for the correlations between variables. P < 0.05 was considered statistically significant. Results: The ONH VD and RNFL thickness were considerably lower in glaucomatous eyes than in healthy eyes (both p < 0.001). Compared with the HTG group, the LTG group had lower VD in the peripapillary region (p = 0.027). Compared with the healthy group, the HTG group had lower PSV (p = 0.029 and = 0.023, respectively), lower EDV (p = 0.023 and < 0.001, respectively), and higher RI (p = 0.019 and = 0.006, respectively) of internal carotid artery (ICA) and central retinal artery (CRA). The LTG group had lower PSV (p = 0.015 and < 0.001, respectively) and EDV (p = 0.047 and = 0.001, respectively) of ophthalmic artery (OA) and CRA. The LTG group had lower PSV of CRA than the HTG group (p = 0.034). In glaucomatous eyes, peripapillary VD had a significant association with the mean defect (MD) (p < 0.001) and RNFL thickness (p < 0.001), but not with the other CDI indices (all p > 0.05). Conclusion: The ONH microcirculation and upstream macrocirculation of the large arteries exhibited differences in the blood flow characteristics between the LTG and HTG groups. These differences may improve our understanding of glaucoma. There was no correlation between the characteristics of the ONH microcirculation and the upstream macrocirculation of large vessels in the LTG and HTG groups