1. Articles from Omer P. Kocaoglu

    1-16 of 16
    1. 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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    2. 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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    3. Imaging human retinal pigment epithelium cells using adaptive optics optical coherence tomography

      Imaging human retinal pigment epithelium cells using adaptive optics optical coherence tomography

      Retinal pigment epithelium (RPE) cells are vital to health of the outer retina, but are often compromised in ageing and major ocular diseases that lead to blindness. Early manifestation of RPE disruption occurs at the cellular level, and while biomarkers at this scale hold considerable promise, RPE cells have proven extremely challenging to image in the living human eye. We present a novel method based on optical coherence tomography (OCT) equipped with adaptive optics (AO) that overcomes the associated technical obstacles. The method takes advantage of the 3D resolution of AO-OCT, but more critically sub-cellular segmentation and registration that permit ...

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    4. Imaging modal content of cone photoreceptors using adaptive optics optical coherence tomography

      Imaging modal content of cone photoreceptors using adaptive optics optical coherence tomography

      It has been long established that photoreceptors capture light based on the principles of optical waveguiding. Yet after decades of experimental and theoretical investigations considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc=785 nm) to noninvasively image in three dimensions the reflectance profiles generated in the inner and outer segments (IS, OS) of cones. Mode content was examined over a range of cone diameters by imaging cones from 0 ...

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    5. Feature Of The Week 01/11/15: Indiana University Demonstrates Adaptive Optics Optical Coherence Tomography at 1 MHz

      Feature Of The Week 01/11/15: Indiana University Demonstrates Adaptive Optics Optical Coherence Tomography at 1 MHz

      Since its first report in 1991, OCT has undergone tremendous advances in almost all aspects of its underlying technologies and methods. For ophthalmic imaging, one of the most impactful advances has been the substantial improvement in image acquisition speed. Increased speed has enabled larger fields of view (FOV) of the retina to be imaged faster and with finer spatial and temporal sampling than ever before. These have greatly expanded the scientific and clinical utility of OCT and have opened new directions into imaging both structure and function of the retina. In this paper, we demonstrate a novel quad-spectrometer adaptive optics ...

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    6. Adaptive-optics optical coherence tomography processing using a graphics processing unit

      Adaptive-optics optical coherence tomography processing using a graphics processing unit

      Graphics processing units are increasingly being used for scientific computing for their powerful parallel processing abilities, and moderate price compared to super computers and computing grids. In this paper we have used a general purpose graphics processing unit to process adaptive-optics optical coherence tomography (AOOCT) images in real time. Increasing the processing speed of AOOCT is an essential step in moving the super high resolution technology closer to clinical viability.

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    7. Adaptive optics optical coherence tomography at 1 MHz

      Adaptive optics optical coherence tomography at 1 MHz

      Image acquisition speed of optical coherence tomography (OCT) remains a fundamental barrier that limits its scientific and clinical utility. Here we demonstrate a novel multi-camera adaptive optics (AO-)OCT system for ophthalmologic use that operates at 1 million A-lines/s at a wavelength of 790 nm with 5.3 μm axial resolution in retinal tissue. Central to the spectral-domain design is a novel detection channel based on four high-speed spectrometers that receive light sequentially from a 1 × 4 optical switch assembly. Absence of moving parts enables ultra-fast (50ns) and precise switching with low insertion loss (−0.18 dB per channel ...

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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. 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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    15. 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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    16. 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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    1-16 of 16
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    1. (16 articles) Indiana University
    2. (16 articles) Donald T. Miller
    3. (16 articles) Omer P. Kocaoglu
    4. (11 articles) Ravi S. Jonnal
    5. (9 articles) Zhuolin Liu
    6. (7 articles) Qiang Wang
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    Volumetric retinal imaging with ultrahigh-resolution spectral-domain optical coherence tomography and adaptive optics using two broadband light sources 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 3D imaging of cone photoreceptors over extended time periods using optical coherence tomography with adaptive optics Imaging retinal nerve fiber bundles using optical coherence tomography with adaptive optics Phase-sensitive imaging of the outer retina using optical coherence tomography and adaptive optics Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors Adaptive optics optical coherence tomography with dynamic retinal tracking Adaptive optics optical coherence tomography at 1 MHz Feature Of The Week 01/11/15: Indiana University Demonstrates Adaptive Optics Optical Coherence Tomography at 1 MHz Remote scanning for ultra-large field of view in wide-field microscopy and full-field OCT Inadequate Intimal Angiogenesis as a Source of Coronary Plaque Instability