Abstract
PURPOSE: Vascular dysfunction is considered a factor contributing to glaucomatous damage. Imaging the bulbar conjunctiva offers a noninvasive approach for directly assessing systemic microcirculation. The purpose of the current study was to test the hypothesis that there is an association between alterations in conjunctival venular hemodynamic biomarkers and presence of primary open-angle glaucoma (POAG). METHODS: This cross-sectional study included 26 normal control (NC) and 29 POAG subjects. Conjunctival microcirculation was assessed non-invasively by combining video microscopy and an automated software to measure the following conjunctival venular hemodynamic biomarkers: vessel diameter (D), blood velocity (V), blood flow (Q), wall shear rate (WSR), and wall shear stress (WSS). RESULTS: Age differed between NC and POAG groups (P < 0.001), while other ocular and systemic factors were not significantly different (P ≥ 0.05). Conjunctival venular V, WSR, and WSS were significantly reduced in POAG compared to NC, both with and without adjusting for covariates and accounting for multiple comparisons (adjusted P ≤ 0.03). In the adjusted models, the differences in conjunctival venular D and Q between NC and POAG groups were not significant (P ≥ 0.16). CONCLUSIONS: The finding of reduced conjunctival venular wall shear stress in POAG supports the vascular theory of glaucoma, implicating endothelial dysfunction. Conjunctival wall shear stress may serve as a novel biomarker for glaucomatous vascular damage. TRANSLATIONAL RELEVANCE: Assessment of microvasculature wall shear stress may serve as a novel biomarker of endothelium function with the potential to improve the understanding, diagnosis and monitoring of glaucoma and other optic neuropathies.