BACKGROUND: Using laser speckle flowgraphy to calculate retinal blood flow, we sought to measure changes in optic nerve blood flow compared to the normal fellow eye (relative blood flow) and changes in vision in patients with central retinal artery occlusions of varying duration. METHODS: Laser speckle flowgraphy was used to measure optic nerve blood flow in eyes with central retinal artery occlusions and the normal fellow eye of patients seen at Beth Israel Deaconess Medical Center to calculate relative blood flow. Visual acuity was assessed monocularly using Snellen Charts in a standardized fashion. RESULTS: In healthy control patients (n=20), relative blood flow was calculated to be 1.02 (p= 0.6843), indicating no significant difference in blood flow between eyes. In patients with unilateral central retinal artery occlusions (n=7), relative blood flow was calculated to be 0.66 ± 0.13 (p < .001), indicating on average a 33 percent loss in blood flow through the optic nerve head. When comparing relative blood flow values of CRAO patients measured within one year of vision loss versus patients when measured after one year of reported vision loss, values of patients measured within one year were lower. CONCLUSIONS AND RELEVANCE: Laser Speckle Flowgraphy has been shown to be a useful diagnostic tool that can reliably provide quantitative information on retinal blood flow. Results suggest that blood flow through the optic nerve head does return over time, presumably as the occlusion resolves or recanalizes. Longitudinal analysis determined a higher relative blood flow in patients one-year post incident versus within one year. However no statistically significant difference in visual acuity between these groups was found, indicating that return of blood flow is not associated with a return in visual acuity. Relative blood flow may be a useful measure of retinal perfusion in other retinal vascular disorders.

This research investigates various applications of diffuse correlation spectroscopy (DCS) on in-vivo human muscle tissue, both at rest and during dynamic exercise. Previously suspected muscle tissue relative blood flow (rBF) baseline shift during extended measurement with DCS and DCS-Near infrared spectroscopy (NIRS) hybrid optical systems are verified, quantified, and resolved by redesign of optical probe and alteration in optical probe attachment methodology during 40 minute supine bed rest baseline measurements. We then translate previously developed occlusion techniques, whereby rBF and relative oxygen consumption rV̇O2 are calibrated to initial resting absolute values by use of a venous occlusion (VO) and arterial occlusion (AO) protocol, respectively, to the lower leg (gastrocnemius) and these blood flows are cross validated at rest by strain gauge venous plethysmography (SGVP). Methods used to continuously observe 0.5Hz, 30% maximum voluntary isometric contraction (MVIC) plantar flexion exercise via dynamometer are adapted for our hybrid DCS-Imagent diffuse optical flow-oximeter in the medial gastrocnemius. We obtain healthy control muscle tissue hemodynamic profiles for key parameters BF, V̇O2, oxygen saturation (StO2), deoxyhemoglobin, oxyhemoglobin, and total hemoglobin concentrations ([Hb], [HbO2], and THC respectively), as well as systemic mean arterial pressure (MAP) and pulse rate (PR), at rest, during VO/AO, during dynamic exercise and during 15 minute recovery periods. Next, we began investigation of muscle tissue hemodynamic disease states by performing a feasibility pilot study using limited numbers of controls and peripheral arterial disease (PAD) patients using the translated methods/techniques to determine the ability of our technology to assess differences in these populations.