Dynamic Alterations in Blood Flow in Glaucoma Measured with Laser Speckle Contrast Imaging.

Abstract Objective To assess the repeatability of blood flow velocity index (BFVi) metrics obtained with a recently FDA-cleared laser speckle contrast imaging device, the XyCAM RI, and characterize differences in these metrics between control, glaucoma suspect, and glaucoma subjects. Design Prospective observational study Participants 46 subjects (20 control, 16 glaucoma suspect, and 10 glaucoma; one eye per subject) Methods Key dynamic BFVi metrics–mean, peak, dip, volumetric rise index (VRI), volumetric fall index (VFI), time to rise (TtR), time to fall (TtF), blow out time (BOT), skew, acceleration time index (ATI)–were measured in the optic disc, optic disc vessels, optic disc perfusion region, and macula in four imaging sessions on the same day. Intrasession and intersession variability were calculated using the coefficient of variation (CV) for each metric in each region of interest (ROI). Values for each dynamic BFVi variable were compared between glaucoma subjects, glaucoma suspects, and controls using bivariate and multivariable analysis. Pearson correlation coefficients were used to correlate each variable in each ROI with age, intraocular pressure, cup to disc ratio, mean deviation, pattern standard deviation, retinal nerve fiber layer thickness, and minimum rim width. Main outcome measures CV for the intrasession and intersession variability for each dynamic BFVi metric in each ROI, and differences in each metric in each ROI between each diagnostic group. Results The intersession CV for mean, peak, dip, as well as VRI, VFI, TtR, and TtF ranged from 3.2 ± 2.5% to 11.0 ± 3.8%. Age, cup-to-disc ratio, optical coherence tomography metrics, and visual field metrics showed significant correlations with dynamic BFVi variables. Peak, mean, dip, VRI, and VFI, were significantly lower in glaucoma subjects than in control subjects in all ROI except the fovea. These metrics were also significantly lower in glaucoma subjects than suspects in the disc vessels. Conclusions Dynamic blood flow metrics measured with the XyCAM RI are reliable, associated with structural and functional glaucoma metrics, and significantly different between glaucoma subjects, glaucoma suspects, and controls. The XyCAM RI may serve as an important tool in glaucoma management in the future.