Vascular biomarkers from optical coherence tomography angiography and glaucoma: where do we stand in 2021?

Abstract

Biomarkers of ocular blood flow originating from a wide variety of imaging modalities have been associated with glaucoma onset and progression for many decades. Advancements in imaging platforms including optical coherence tomography angiography (OCTA) have provided the ability to quantify vascular changes in glaucoma patients, alongside traditional measures such as retinal nerve fibre layer thickness and optic nerve head structure. Current literature on vascular biomarkers, as measured by OCTA, indicates significant relationships between glaucoma and blood flow and capillary density in the retina and ONH. The data currently available, however, are highly diverse and lack robust longitudinal data on OCTA vascular outcomes and glaucoma progression. Herein we discuss and summarize the relevant current literature on OCTA vascular biomarkers and glaucoma reviewed through March 1, 2021. Associations between OCTA vascular biomarkers and clinical structural and functional glaucoma outcomes as well as differences between glaucoma patients and healthy controls are reviewed and summarized. The available data identify significantly decreased flow density, flow index and vessel density in the ONH, peripapillary vascular layer and macula of glaucoma patients compared with controls. Whole image vessel density is also significantly decreased in glaucoma patients compared with controls, and this outcome has been found to correspond to severity of visual field loss. OCTA vascular biomarkers alongside clinical structural outcomes may aid in assessing overall risk for glaucoma in patients.

The Development and Clinical Application of Innovative Optical Ophthalmic Imaging Techniques

“…OCT-A scans from macular and ONH scans in glaucoma have been shown to display good reproducibility, which supports the use of OCT-A longitudinally as well ( 73 ). Vessel density parameters have also been associated with visual field progression ( 74 , 75 ).…”

Heterogeneity of Ocular Hemodynamic Biomarkers among Open Angle Glaucoma Patients of African and European Descent

“…Optical coherence tomography angiography (OCTA) allows simultaneous assessments of retinal and optic nerve head (ONH) structure and vascular densities (VD), providing clinicians an improved user interface for the potential inclusion of vascular biomarkers [ 2 ]. Since its introduction, OCTA data from a wide range of studies have suggested a significant reduction in the mean peripapillary VD in glaucoma patients, as well as marked reduction in VD in the ONH and parafoveal regions [ 3 ].…”

“…Since its introduction, OCTA data from a wide range of studies have suggested a significant reduction in the mean peripapillary VD in glaucoma patients, as well as marked reduction in VD in the ONH and parafoveal regions [ 3 ]. The associations of OCTA VD outcomes and OAG are generally strong, suggesting lower VD of the peripapillary retina, ONH and macular regions in glaucoma patients when compared to healthy controls [ 2 , 3 ]. A recent study in a Chinese population found that significant microvascular damage assessed by OCTA was present in both macular and peripapillary regions in early OAG patients, with VD loss highest in peripheral regions [ 4 ].…”

“…The principles of operation for OCTA involve utilization of ocular structures, light dynamics and tissue pigment levels, all of which may differ between persons with OAG and therefore bias device outcomes [ 1 , 2 , 3 , 5 , 7 , 8 , 9 ]. Mitigating potential bias in ophthalmic diagnostic utilities is essential to reduce disparities in treatment outcomes currently experienced by OAG patients of African descent (AD) [ 10 ].…”

Effects of Tafluprost on Ocular Blood Flow

“…Studies have shown that parameters including blood flow density, blood flow index, and vessel density (VD) in the optic nerve head (ONH), peripapillary vascular layer, and macula decrease significantly in patients with glaucoma [ 7 – 14 ]. Furthermore, the decreased ocular blood flow (OBF) is closely related to the occurrence and development of glaucomatous optic neuropathy.…”