A Pilot Study Assessing Retinal Blood Flow Dysregulation in Glaucoma Using Erythrocyte Mediated Velocimetry

Abstract

Purpose The purpose of this study was to compare autoregulation of retinal arteriolar and venular blood flow in patients with glaucoma, glaucoma suspect participants, and control participants using erythrocyte mediated velocimetry. Methods This prospective cohort pilot study included 7 eyes of 5 participants with glaucoma, 15 eyes of 8 glaucoma suspect participants, and 11 eyes of 6 control participants. Mean erythrocyte velocity in retinal arterioles and venules was measured using erythrocyte mediated velocimetry at room air and after oxygen supplementation. Change in erythrocyte velocity was compared among all groups using generalized estimating equations. Results In total, 64 vessels (18 with glaucoma, 31 that were glaucoma suspect, and 15 controls) of 33 eyes of 19 participants were analyzed. There was no significant difference in baseline velocities in arterioles or venules among the three groups. With induction of hyperoxia, mean arterial erythrocyte velocity decreased in glaucoma (−7.2 ± 13.7%), which differed from controls and glaucoma suspects where erythrocyte velocity increased with hyperoxia by 4.6 ± 13.3% ( P = 0.002) and 7.2 ± 21.7% ( P = 0.03), respectively. A higher baseline arteriolar velocity (β = −3.9% per mm/s, P = 0.002), glaucoma diagnosis (β = −21.1%, P = 0.03), and White race (β = −20.0%, P = 0.01) were associated with decreased velocity in response to arterial hyperoxia. Conclusions Hyperoxia increased erythrocyte velocity in control and glaucoma suspect participants, but decreased erythrocyte velocity in glaucoma participants, possibly due to impaired autoregulation. Baseline velocity, glaucoma diagnosis, and White race were associated with a decrease in velocity with induction of hyperoxia. Translational Relevance The European Medicines Agency (EMA) permits precision measurements of blood flow which may aid in the development of biomarkers of glaucoma-related dysregulation of blood flow.

Current State of Knowledge in Ocular Blood Flow in Glaucoma: A Narrative Review

“…By analyzing the SLO images, healthcare professionals can evaluate the blood flow patterns, identify any abnormalities or blockages, and assess the health of the retinal vasculature. 60 SLO is particularly useful as multicolor imaging 61 and auto fluorescence imaging to identify reduced blood flow in the retina, choroid, and optic nerve head demonstrating its potential in diagnosing glaucoma. 62 …”

“… Correlations with visual field sensitivity and the favorable floor effect compared indicates LST as a promising clinical tool to monitor progression in late-stage glaucoma. Chen 2022 60 Blue Field Entoptic Technique Can measure leukocyte speed in retinal perifoveal vessels This technique can provide precision measurements of blood flow which can be set as a biomarker of glaucoma related dysregulation of blood flow in glaucoma. Rolle 2019 61 Heidelberg Retinal Flowmetry (HRF) Measures the mean values of velocity, volume, and flow measurements using uses low laser light intensities HRF has been reported to identify vessel densities and diminished microvascular network in POAG eyes.…”