1. Articles from ravi s. jonnal

    1-23 of 23
    1. Coextensive synchronized SLO-OCT with adaptive optics for human retinal imaging

      Coextensive synchronized SLO-OCT with adaptive optics for human retinal imaging

      We describe the details of a multimodal retinal imaging system which combines adaptive optics (AO) with an integrated scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT) imaging system. The OCT subsystem consisted of a swept-source, Fourier-domain mode-locked (FDML) laser, with a very high A-scan rate (1.6 MHz), whose beam was raster scanned on the retina by two scanners—one resonant scanner and one galvanometer. The high sweep rate of the FDML permitted the SLO and OCT to utilize the same scanners for in vivo retinal imaging and, unlike existing multimodal systems, concurrently acquired SLO frames and OCT volumes ...

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    2. 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 perspectives .With emerging approaches such as gene therapy, stem cell therapy, and transplantation, there is new hope for rescuing existing dysfunctional photoreceptors. A critical aspect of these therapeutic approaches is ...

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    3. 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 of 1063 nm and an AO system operating in closed-loop. Analysis of serial volumetric images revealed phase changes of cone photoreceptors consistent with outer segment elongation and proportional to stimulus ...

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    4. 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 methods–in which fast-axis strips from target images are registered to a reference frame–have been applied in adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT). This approach has enabled object tracking and frame averaging, and methods have been described to automatically select reference frames with minimal motion. However, inconspicuous motion artifacts may persist in reference frames and propagate themselves throughout the ...

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    5. 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, and an AO subsystem providing diffraction-limited imaging. Analysis of serial volumetric images revealed phase changes of cone photoreceptors consistent with outer segment elongation and proportional to stimulus intensity, as well ...

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    6. 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 cones. Lateral structure was characterized by correlation of band 3 with band 2 and comparison of their power spectra. Band thickness and separation were also measured in a clinical OCT ...

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    7. 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, we report discovery of the optical signature associated with disc shedding using a method based on adaptive optics optical coherence tomography (AO-OCT) in conjunction with post-processing methods to track and ...

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    8. 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 combine the microscopic transverse resolution of AO with the microscopic axial resolution of OCT, building AO-OCT systems with the highest three-dimensional resolution of any existing retinal imaging modality. Methods : We ...

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    9. 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 and segmented in three dimensions using custom software. Features corresponding to bands 1, 2, and 3 were automatically identified. Thickness of band 2 was assessed in each cell by fitting ...

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    10. Adaptive optics optical coherence tomography with dynamic retinal tracking

      Adaptive optics optical coherence tomography with dynamic retinal tracking

      Adaptive optics optical coherence tomography (AO-OCT) is a highly sensitive and noninvasive method for three dimensional imaging of the microscopic retina. Like all in vivo retinal imaging techniques, however, it suffers the effects of involuntary eye movements that occur even under normal fixation. In this study we investigated dynamic retinal tracking to measure and correct eye motion at KHz rates for AO-OCT imaging. A customized retina tracking module was integrated into the sample arm of the 2nd-generation Indiana AO-OCT system and images were acquired on three subjects. Analyses were developed based on temporal amplitude and spatial power spectra in conjunction ...

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    11. 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 at 1.5° temporal to the fovea over 75 and 105 minutes in two subjects. Volumes were dewarped and registered, after which the cone intensity, OS length, and referenced phase ...

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    12. Phase-sensitive imaging of the outer retina using optical coherence tomography and adaptive optics

      Phase-sensitive imaging of the outer retina using optical coherence tomography and adaptive optics
      The cone photoreceptor’s outer segment (OS) experiences changes in optical path length, both in response to visible stimuli and as a matter of its daily course of renewal and shedding. These changes are of interest, to quantify function in healthy cells and assess dysfunction in diseased ones. While optical coherence tomography (OCT), combined with adaptive optics (AO), has permitted unprecedented three-dimensional resolution in the living retina, it has not generally been able to measure these OS dynamics, whose scale is smaller than OCT’s axial resolution of a few microns. A possible solution is to take advantage of the ...
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    13. Imaging retinal nerve fiber bundles using optical coherence tomography with adaptive optics

      Imaging retinal nerve fiber bundles using optical coherence tomography with adaptive optics
      Early detection of axonal tissue loss in retinal nerve fiber layer (RNFL) is critical for effective treatment and management of diseases such as glaucoma. This study aims to evaluate the capability of ultrahigh-resolution optical coherence tomography with adaptive optics (UHR-AO-OCT) for imaging the RNFL axonal bundles (RNFBs) with 3 × 3 × 3 μm3 resolution in the eye. We used a research-grade UHR-AO-OCT system to acquire 3° × 3° volumes in four normal subjects and one subject with an arcuate retinal nerve fiber layer defect (n = 5; 29–62 years). Cross section (B-scans) and en face (C-scan) slices extracted from the volumes were ...
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    14. Imaging cone photoreceptors in three dimensions and in time using ultrahigh resolution optical coherence tomography with adaptive optics

      Imaging cone photoreceptors in three dimensions and in time using ultrahigh resolution optical coherence tomography with adaptive optics
      Cone photoreceptors in the living human eye have recently been imaged with micron-scale resolution in all three spatial dimensions using adaptive optics optical coherence tomography. While these advances have allowed non-invasive study of the three-dimensional structure of living human cones, studies of their function and physiology are still hampered by the difficulties to monitor the same cells over time. The purpose of this study is to demonstrate the feasibility of cone monitoring using ultrahigh-resolution adaptive optics optical coherence tomography. Critical to this is incorporation of a high speed CMOS camera (125 KHz) and a novel feature-based, image registration/dewarping algorithm ...
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    15. 3D imaging of cone photoreceptors over extended time periods using optical coherence tomography with adaptive optics

      3D imaging of cone photoreceptors over extended time periods using optical coherence tomography with adaptive optics

      Optical coherence tomography with adaptive optics (AO-OCT) is a highly sensitive, noninvasive method for 3D imaging of the microscopic retina. The purpose of this study is to advance AO-OCT technology by enabling repeated imaging of cone photoreceptors over extended periods of time (days). This sort of longitudinal imaging permits monitoring of 3D cone dynamics in both normal and diseased eyes, in particular the physiological processes of disc renewal and phagocytosis, which are disrupted by retinal diseases such as age related macular degeneration and retinitis pigmentosa. For this study, the existing AO-OCT system at Indiana underwent several major hardware and software ...

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    16. Imaging Retinal Capillaries Using Ultrahigh-Resolution Optical Coherence Tomography and Adaptive Optics

      Imaging Retinal Capillaries Using Ultrahigh-Resolution Optical Coherence Tomography and Adaptive Optics
      Purpose: Ultrahigh-resolution optical coherence tomography (UHR-OCT) with adaptive optics (AO) provides micron-scale 3D resolution that is attractive for imaging the retinal microvasculature. Such imaging may be useful for early detection of pathologic changes as in diabetic retinopathy. Here we investigate this potential for detecting individual capillaries in healthy subjects. Methods: UHR-AO-OCT volumes centered on the fovea were acquired from seven subjects (25-61 years) with three pre-selected with no foveal avascular zone (FAZ). Images were compared to entoptic diagrams using the capillaries at the rim of the FAZ. Methods of comparison were: testing for the presence of a FAZ; noting distinct ...
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    17. Retinal imaging with polarization-sensitive optical coherence tomography and adaptive optics

      Retinal imaging with polarization-sensitive optical coherence tomography and adaptive optics

      Various layers of the retina are well known to alter the polarization state of light. Such changes in polarization may be a sensitive indicator of tissue structure and function, and as such have gained increased clinical attention. Here we demonstrate a polarization-sensitive optical coherence tomography (PS-OCT) system that incorporates adaptive optics (AO) in the sample arm and a single line scan camera in the detection arm. We quantify the benefit of AO for PS-OCT in terms of signal-to-noise, lateral resolution, and speckle size. Double pass phase retardation per unit depth values ranging from 0.25°/μm to 0.65°/μm ...

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    18. Volumetric retinal imaging with ultrahigh-resolution spectral-domain optical coherence tomography and adaptive optics using two broadband light sources

      Volumetric retinal imaging with ultrahigh-resolution spectral-domain optical coherence tomography and adaptive optics using two broadband light sources
      Ultrabroadband sources, such as multiplexed superluminescent diodes (SLDs) and femtosecond lasers, have been successfully employed in adaptive optics optical coherence tomography (AO-OCT) systems for ultrahigh resolution retinal imaging. The large cost differential of these sources, however, motivates the need for a performance comparison. Here, we compare the performance of a Femtolasers Integral Ti:Sapphire laser and a Superlum BroadLighter T840, using the same AO-OCT system and the same subject. In addition, we investigate the capability of our instrument equipped with the Integral to capture volume images of the fovea and adjacent regions on a second subject using the AO to ...
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    19. Does transverse chromatic aberration limit performance of AO-OCT retinal imaging?

      The combination of adaptive optics (AO) and optical coherence tomography (OCT) has been successfully applied to in vivo retinal imaging, motivated by the potential of unprecedented 3D resolution. The eye, however, not only suffers from monochromatic aberrations, which are corrected by AO, but also s ... [Proc. SPIE 7139, 71390Z (2008)] published Tue Dec 30, 2008.
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    20. Method and apparatus for improving both lateral and axial resolution in ophthalmoscopy

      The invention provides a method of optical imaging comprising providing a sample to be imaged, measuring and correcting aberrations associated with the sample using adaptive optics, and imaging the sample by optical coherence tomography. The method can be used to image the fundus of a human eye to provide diagnostic information about retinal pathologies such as macular degeneration, retinitis pigmentosa, glaucoma, or diabetic retinopathy. The invention further provides an apparatus comprising an adaptive optics subsystem and a two-dimensional optical coherence tomography subsystem.
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    21. Measuring retinal contributions to the optical Stiles-Crawford effect with optical coherence tomography

      The directional component of the retinal reflection, i.e., the optical Stiles-Crawford effect (SCE), is well established to result from the waveguiding property of photoreceptors. Considerable uncertainty, however, remains as to which retinal reflections are waveguided and thus contribute. To this ... [Opt. Express 16, 6486-6501 (2008)]
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    22. In vivo functional imaging of humancone photoreceptors

      We evaluate a novel non-invasive optical technique for observing fast physiological processes, in particular phototransduction, in single photoreceptor cells in the living human eye. The method takes advantage of the interference of multiple reflections within the outer segments (OS) of cones. ... [Opt. Express 15, 16141-16160 (2007)]

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    1-23 of 23
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  2. Topics in the News

    1. (22 articles) Ravi S. Jonnal
    2. (16 articles) Indiana University
    3. (16 articles) Donald T. Miller
    4. (11 articles) Omer P. Kocaoglu
    5. (9 articles) John S. Werner
    6. (9 articles) Weihua Gao
    7. (9 articles) Robert J. Zawadzki
    8. (7 articles) Barry Cense
    9. (7 articles) Qiang Wang
    10. (7 articles) Mehdi Azimipour
    11. (1 articles) University of Pittsburgh
    12. (1 articles) ESPCI ParisTech
    13. (1 articles) University of Toronto
    14. (1 articles) Felix I. Feldchtein
    15. (1 articles) Mathias Fink
    16. (1 articles) Claude Boccara
    17. (1 articles) I. Alex Vitkin
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    Volumetric retinal imaging with ultrahigh-resolution spectral-domain optical coherence tomography and adaptive optics using two broadband light sources Retinal imaging with polarization-sensitive optical coherence tomography and adaptive optics Imaging Retinal Capillaries Using Ultrahigh-Resolution Optical Coherence Tomography and Adaptive Optics Imaging cone photoreceptors in three dimensions and in time using ultrahigh resolution optical coherence tomography with adaptive optics Imaging retinal nerve fiber bundles using optical coherence tomography with adaptive optics Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors Changes in the OCT angiographic appearance of type 1 and type 2 CNV in exudative AMD during anti-VEGF treatment Optical coherence angiography for pre-treatment assessment and treatment monitoring following photodynamic therapy: a basal cell carcinoma patient study Computational aberration correction in spatiotemporal optical coherence (STOC) imaging A rare entity: Sympathetic ophthalmia presumably after blunt trauma to the phthisical eye and optical coherence tomography angiography metrics to monitor response to treatment Mechanism of fluid leak in non-traumatic corneal perforations: an anterior segment optical coherence tomography study Repeatability of ocular surface vessel density measurements with optical coherence tomography angiography