KEYWORDS: Eye, Hemodynamics, Retina, Imaging systems, In vivo imaging, Cameras, Optical coherence tomography, Signal to noise ratio, Neurophotonics, Tunable filters
SignificanceMicrocirculation and neurovascular coupling are important parameters to study in neurological and neuro-ophthalmic conditions. As the retina shares many similarities with the cerebral cortex and is optically accessible, a special focus is directed to assessing the chorioretinal structure, microvasculature, and hemodynamics of mice, a vital animal model for vision and neuroscience research.AimWe aim to introduce an optical imaging tool enabling in vivo volumetric mouse retinal monitoring of vascular hemodynamics with high temporal resolution.ApproachWe translated the spatio-temporal optical coherence tomography (STOC-T) technique into the field of small animal imaging by designing a new optical system that could compensate for the mouse eye refractive error. We also developed post-processing algorithms, notably for the assessment of (i) localized hemodynamics from the analysis of pulse wave–induced Doppler artifact modulation and (ii) retinal tissue displacement from phase-sensitive measurements.ResultsWe acquired high-quality, in vivo volumetric mouse retina images at a rate of 113 Hz over a lateral field of view of ∼500 μm. We presented high-resolution en face images of the retinal and choroidal structure and microvasculature from various layers, after digital aberration correction. We were able to measure the pulse wave velocity in capillaries of the outer plexiform layer with a mean speed of 0.35 mm/s and identified venous and arterial pulsation frequency and phase delay. We quantified the modulation amplitudes of tissue displacement near major vessels (with peaks of 150 nm), potentially carrying information about the biomechanical properties of the retinal layers involved. Last, we identified the delays between retinal displacements due to the passing of venous and arterial pulse waves.ConclusionsThe developed STOC-T system provides insights into the hemodynamics of the mouse retina and choroid that could be beneficial in the study of neurovascular coupling and vasculature and flow speed anomalies in neurological and neuro-ophthalmic conditions.
We present a novel ultrafast imaging system using Spatio-Temporal Optical Coherence Tomography (STOC-T), capable of acquiring structural images of a mouse retina at a volumetric rate of 112 Hz, aided by a calibrated fundus camera for focal plane adjustment. We extract blood pulse traces from retinal and choroidal vessels using a structural-only OCT analysis, and pulse wave-induced retinal layer displacement from differential OCT phase analysis. With both analyses, we measure hemodynamic parameters, such as the delays between arterial and venous pulsation, to provide a comprehensive suite of potential biomarkers of retinal diseases.
We present a novel ultrafast imaging system using Spatio-Temporal Optical Coherence Tomography (STOC-T), capable of acquiring structural images of a mouse retina at a volumetric rate of 112 Hz. A calibrated fundus camera and white-light illumination aid the alignment of the mouse and the adjustment of the focal plane in the mouse retina for the STOC-T image. We extract pulsatile blood flow frequency and other hemodynamic parameters from multiple retinal and choroidal vessels from structural-only OCT images, highlighting the prospects of STOC-T for monitoring retinal hemodynamics in a simple way.
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