1,462 research outputs found
Convergence of an Explicit Iterative Leap-frog Discontinuous Galerkin Method for Time-domain Maxwell's Equations in Anisotropic Materials
We propose an explicit iterative leap-frog discontinuous Galerkin method for
time-domain Maxwell's equations in anisotropic materials and derive its
convergence properties. The a priori error estimates are illustrated by
numerical means in some experiments. Motivated by a real application which
encompasses modeling electromagnetic wave's propagation through the eye's
structures, we simulate our model in a 2D domain aiming to represent a simple
example of light scattering in the outer nuclear layer of the retina.Comment: 14 pages, 6 figure
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Astigmatism and Pseudoaccommodation in Pseudophakic Eyes
noAdvanced IOLs with circumferential zones of different power provide pseudoaccommodation. We investigated the potential for power variation with meridian, namely astigmatism, to provide pseudo-accommodation. With appropriate power and axis orientations, acceptable pseudo-accommodation can be achieved
Retinal and choroidal capillary imaging by optical coherence tomography
Thesis (Ph. D. in Engineering)--University of Tsukuba, (A), no. 6395, 2013.3.25Includes bibliographical references (p. 55-64
Parafoveal Retinal Vascular Response to Pattern Visual Stimulation Assessed with OCT Angiography
We used optical coherence tomography (OCT) angiography with a high-speed swept-source OCT system to investigate retinal blood flow changes induced by visual stimulation with a reversing checkerboard pattern. The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to quantify blood flow as measured with parafoveal flow index (PFI), which is proportional to the density of blood vessels and the velocity of blood flow in the parafoveal region of the macula. PFI measurements were taken in 15 second intervals during a 4 minute period consisting of 1 minute of baseline, 2 minutes with an 8 Hz reversing checkerboard pattern stimulation, and 1 minute without stimulation. PFI measurements increased 6.1±4.7% (p = .001) during the first minute of stimulation, with the most significant increase in PFI occurring 30 seconds into stimulation (p<0.001). These results suggest that pattern stimulation induces a change to retinal blood flow that can be reliably measured with OCT angiography.National Institutes of Health (U.S.) (Grant R01 EY013516)National Institutes of Health (U.S.) (Grant Rosenbaum's P30EY010572)Research to Prevent Blindness, Inc. (United States) (Grant R01-Ey11289-26)United States. Air Force Office of Scientific Research (FA9550-10-1-0551
Beyond backscattering: Optical neuroimaging by BRAD
Optical coherence tomography (OCT) is a powerful technology for rapid
volumetric imaging in biomedicine. The bright field imaging approach of
conventional OCT systems is based on the detection of directly backscattered
light, thereby waiving the wealth of information contained in the angular
scattering distribution. Here we demonstrate that the unique features of
few-mode fibers (FMF) enable simultaneous bright and dark field (BRAD) imaging
for OCT. As backscattered light is picked up by the different modes of a FMF
depending upon the angular scattering pattern, we obtain access to the
directional scattering signatures of different tissues by decoupling
illumination and detection paths. We exploit the distinct modal propagation
properties of the FMF in concert with the long coherence lengths provided by
modern wavelength-swept lasers to achieve multiplexing of the different modal
responses into a combined OCT tomogram. We demonstrate BRAD sensing for
distinguishing differently sized microparticles and showcase the performance of
BRAD-OCT imaging with enhanced contrast for ex vivo tumorous tissue in
glioblastoma and neuritic plaques in Alzheimer's disease
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