1. Ravi S. Jonnal

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    1. Mentioned In 24 Articles

    2. ADAPTIVE OPTICS OPHTHALMOSCOPY CONFERENCE SEPTEMBER 4TH, PARIS

      ADAPTIVE OPTICS OPHTHALMOSCOPY CONFERENCE SEPTEMBER 4TH, PARIS
      Late Summer Course - September 4 5, 2019 - Paris High resolution imaging technologies, exemplified by adaptive optics ophthalmoscopy (AOO) and optical coherence tomography (OCT) are progressively transferring from the lab to the clinic. This is an opportunity to better understand retinal diseases, to optimize their management but also to provide novel biomarkers for other medical specialities. However, there is still an unmet need in the field of clinical interpretation of AOO ...
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    3. Feature Of The Week 03/01/2019: Functional Retina lmaging using Adaptive Optics Swept-Source OCT at 1.6 MHz

      Feature Of The Week 03/01/2019: Functional Retina lmaging using Adaptive Optics Swept-Source OCT at 1.6 MHz
      Functional assessment of the retina is a critical part of both clinical ophthalmology and vision research. Several techniques exist for measuring retinal function, such as Visual acuity/contrast sensitivity tests, Psychophysics and ERG (Electroretinogram and multifocal Electroretinogram). However, these approaches have important limitations, poor spatial resolution, slightly invasive; long duration of tests. There is great excitement about emerging noninvasive approaches to measuring retinal function, both from clinical and basic scientific ...
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    4. Functional retinal imaging using adaptive optics swept-source OCT at 1.6  MHz

      Functional retinal imaging using adaptive optics swept-source OCT at 1.6  MHz
      Objective optical assessment of photoreceptor function may permit earlier diagnosis of retinal disease than current methods such as perimetry, electrophysiology, and clinical imaging. In this work, we describe an adaptive optics (AO) optical coherence tomography (OCT) system designed to measure functional responses of single cones to visible stimuli. The OCT subsystem consisted of a raster-scanning Fourier-domain mode-locked laser that acquires A scans at 1.64 MHz with a center wavelength ...
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    5. UC Davis Receives NIH Grant for Studying Properties of Photoreceptors and Muller Cells Investigated with AO-OCT

      UC Davis Receives NIH Grant for Studying Properties of Photoreceptors and Muller Cells Investigated with AO-OCT
      University of California Davis Receives a 2019 NIH Grant for $245,479 for Properties of Photoreceptors and Muller Cells Investigated with AO-OCT. The principal investigator is Ravi Jonnal. The program began in 2016 and ends in 2020. Below is a summary of the proposed work. The research proposed for this award will examine functional and structural properties of single cells in the human retina. The three Aims will link the ...
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    6. Intraframe motion correction for raster-scanned adaptive optics images using strip-based cross-correlation lag biases

      Intraframe motion correction for raster-scanned adaptive optics images using strip-based cross-correlation lag biases
      In retinal raster imaging modalities, fixational eye movements manifest as image warp, where the relative positions of the beam and retina change during the acquisition of single frames. To remove warp artifacts, strip-based registration methodsin which fast-axis strips from target images are registered to a reference framehave been applied in adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT). This approach has enabled object tracking and frame ...
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    7. Functional retinal imaging using adaptive optics swept-source OCT at 1.6MHz

      Functional retinal imaging using adaptive optics swept-source OCT at 1.6MHz
      bjective optical assessment of photoreceptor function may permit earlier diagnosis of retinal disease than current methods such as perimetry, electrophysiology, and clinical imaging. In this work, we describe an adaptive optics (AO) optical coherence tomography (OCT) system designed to measure functional responses of single cones to visible stimuli. The OCT subsystem consisted of a raster-scanning Fourier-domain mode-locked laser that acquires A-scans at 1.64MHz with a center wavelength of 1063nm ...
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    8. The Properties of Outer Retinal Band Three Investigated With Adaptive-Optics Optical Coherence Tomography

      The Properties of Outer Retinal Band Three Investigated With Adaptive-Optics Optical Coherence Tomography
      Purpose : Optical coherence tomography's (OCT) third outer retinal band has been attributed to the zone of interdigitation between RPE cells and cone outer segments. The purpose of this paper is to investigate the structure of this band with adaptive optics (AO)-OCT. Methods : Using AO-OCT, images were obtained from two subjects. Axial structure was characterized by measuring band 3 thickness and separation between bands 2 and 3 in segmented ...
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    9. Imaging of the human choroid with a 1.7 MHz A-scan rate FDML swept source OCT system

      Imaging of the human choroid with a 1.7 MHz A-scan rate FDML swept source OCT system
      We demonstrate OCT angiography (OCTA) and Doppler OCT imaging of the choroid in the eyes of two healthy volunteers and in a geographic atrophy case. We show that visualization of specific choroidal layers requires selection of appropriate OCTA methods. We investigate how imaging speed, B-scan averaging and scanning density influence visualization of various choroidal vessels. We introduce spatial power spectrum analysis of OCT en face angiographic projections as a method ...
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    10. UCDavis Receives NIH Grant for Properties of Photoreceptoers and Muller Cells Investigated with AO-OCT

      UCDavis Receives NIH Grant for Properties of Photoreceptoers and Muller Cells Investigated with AO-OCT
      The University of California at Davis Receives a 2017 NIH Grant for $97,834 for Properties of Photoreceptoers and Muller Cells Investigated with AO-OCT. The principal investigator is Ravi Jonnal. The program began in 2016 and ends in 2017. Below is a summary of the proposed work. The research proposed for this award will examine functional and structural properties of single cells in the human retina. The three Aims will ...
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    11. Photoreceptor disc shedding in the living human eye

      Photoreceptor disc shedding in the living human eye
      Cone photoreceptors undergo a daily cycle of renewal and shedding of membranous discs in their outer segments (OS), the portion responsible for light capture. These physiological processes are fundamental to maintaining photoreceptor health, and their dysfunction is associated with numerous retinal diseases. While both processes have been extensively studied in animal models and postmortem eyes, little is known about them in the living eye, in particular human. In this study ...
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    12. A Review of Adaptive Optics Optical Coherence Tomography: Technical Advances, Scientific Applications, and the Future

      A Review of Adaptive Optics Optical Coherence Tomography: Technical Advances, Scientific Applications, and the Future
      Purpose : Optical coherence tomography (OCT) has enabled virtual biopsy of the living human retina, revolutionizing both basic retina research and clinical practice over the past 25 years. For most of those years, in parallel, adaptive optics (AO) has been used to improve the transverse resolution of ophthalmoscopes to foster in vivo study of the retina at the microscopic level. Here, we review work done over the last 15 years to ...
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    13. The cellular origins of the outer retinal bands in optical coherence tomography images

      The cellular origins of the outer retinal bands in optical coherence tomography images
      Purpose: To test the recently proposed hypothesis that the second OCT outer retinal band originates from the inner segment ellipsoid, by measuring: 1) thickness of this band within single cones, and 2) its respective distance from the external limiting membrane and outer segment tips. Methods: Adaptive optics OCT images were obtained from four normal subjects. Images were obtained at foveal (2∘) and perifoveal (5∘) locations. Cones (n = 9593) were identified ...
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    14. Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors

      Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors
      Optical coherence tomography with adaptive optics (AO-OCT) is a noninvasive method for imaging the living retina at the microscopic level. We used AO-OCT technology to follow changes in cone photoreceptor outer segment (OS) length and reflectance. To substantially increase sensitivity of the length measurements, a novel phase retrieval technique was demonstrated, capable of detecting changes on a nanometer scale. We acquired volume videos of 0.65°x0.65° retinal patches ...
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  2. About Ravi S. Jonnal

    Ravi S. Jonnal

    Ravi S. Jonnal is a project scientist at UC Davis.