1. Articles from Gerhard Garhofer

    1-12 of 12
    1. Automatic assessment of tear film and tear meniscus parameters in healthy subjects using ultrahigh-resolution optical coherence tomography

      Automatic assessment of tear film and tear meniscus parameters in healthy subjects using ultrahigh-resolution optical coherence tomography

      Many different parameters exist for the investigation of tear film dynamics. We present a new tear meniscus segmentation algorithm which automatically extracts tear meniscus area (TMA), height (TMH), depth (TMD) and radius (TMR) from UHR-OCT measurements and apply it to a data set including repeated measurements from ten healthy subjects. Mean values and standard deviations are 0.0174 ± 0.007 mm 2 , 0.272 ± 0.069 mm, 0.191 ± 0.049 mm and 0.309 ± 0.123 mm for TMA, TMH, TMD and TMR, respectively. A significant correlation was found between all respective tear meniscus parameter pairs (all p < 0 ...

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    2. Ultrahigh‐resolution anterior segment optical coherence tomography for analysis of corneal microarchitecture during wound healing

      Ultrahigh‐resolution anterior segment optical coherence tomography for analysis of corneal microarchitecture during wound healing

      Purpose To employ ultrahigh‐resolution (UHR) optical coherence tomography (OCT) for investigation of the early wound healing process in corneal epithelium. Methods A custom‐built UHR‐OCT system assessed epithelial healing in human keratoconic cornea after epi‐off crosslinking (CXL) procedure and a wound healing model in rabbits with iatrogenic corneal injury. 3D OCT data sets enhanced obtaining epithelial thickness maps and evaluation of reepithelization stage. Accompanying changes in deeper corneal microarchitecture were analysed. Results The mean central corneal thickness in 40 eyes with keratoconus at baseline was 482.7 ± 38.2 μ m, while mean central epithelial thickness (CET) was ...

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    3. Ultrahigh-resolution OCT imaging of the human cornea

      Ultrahigh-resolution OCT imaging of the human cornea

      We present imaging of corneal pathologies using optical coherence tomography (OCT) with high resolution. To this end, an ultrahigh-resolution spectral domain OCT (UHR-OCT) system based on a broad bandwidth Ti:sapphire laser is employed. With a central wavelength of 800 nm, the imaging device allows to acquire OCT data at the central, paracentral and peripheral cornea as well as the limbal region with 1.2 µm x 20 µm (axial x lateral) resolution at a rate of 140 000 A-scans/s. Structures of the anterior segment of the eye, not accessible with commercial OCT systems, are visualized. These include corneal ...

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    4. Effect of different lubricant eye gels on tear film thickness as measured with ultrahigh-resolution optical coherence tomography

      Effect of different lubricant eye gels on tear film thickness as measured with ultrahigh-resolution optical coherence tomography

      Purpose To compare the effect of a single drop of different lubricant eye gels on tear film thickness (TFT) as measured with ultrahigh-resolution optical coherence tomography (UHR-OCT) in patients with mild-to-moderate dry eye disease (DED). Methods The study followed a randomized, single-masked, observer-blinded parallel group design. Patients received a single dose of either unpreserved trehalose 3% + hyaluronic acid 0.15% (TH), hyaluronic acid 0.2% (HA) or polyethylene glycol 0.4% + propylene glycol 0.3% (PP) eye drops. In total, 60 patients were included and TFT was measured using a custom-built UHR-OCT system. Results The mean TFT at baseline was ...

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    5. Estimating Retinal Blood Flow Velocities by Optical Coherence Tomography

      Estimating Retinal Blood Flow Velocities by Optical Coherence Tomography

      Importance While optical coherence tomography (OCT) angiography has been considered to evaluate retinal capillary blood flow instead of fluorescein angiography, the reflectance pattern of blood vessels on structural OCT might also provide retinal capillary flow data in the absence of fluorescein angiography. This potential has been insufficiently explored, despite promising data concerning a possible relationship between the reflectance pattern of blood vessels and their perfusion velocity in a laboratory setting. Objective To evaluate the potential of retinal blood flow velocity estimation by structural OCT. Design, Setting, and Participants Cross-sectional observational study conducted from June to November 2015 at a tertiary ...

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    6. Measurement of Retinal Vascular Caliber From Optical Coherence Tomography Phase Images

      Measurement of Retinal Vascular Caliber From Optical Coherence Tomography Phase Images

      Purpose : To compare retinal vessel calibers extracted from phase-sensitive optical coherence tomography (OCT) images with vessel calibers as obtained from the Retinal Vessel Analyzer (RVA). Methods : Data from previously published studies in 13 healthy subjects breathing room air ( n = 214 vessels) and 7 subjects breathing 100% oxygen ( n = 101 vessels) were used. Vessel calibers from OCT phase images were measured vertically along the optical axis by three independent graders. The data from RVA fundus images were corrected for magnification to obtain absolute values. Results : The average vessel diameter as obtained from OCT images during normoxia was lower than from RVA ...

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    7. In vivo tear film thickness measurement and tear film dynamics visualization using spectral domain optical coherence tomography

      In vivo tear film thickness measurement and tear film dynamics visualization using spectral domain optical coherence tomography

      Dry eye syndrome is a highly prevalent disease of the ocular surface characterized by an instability of the tear film. Traditional methods used for the evaluation of tear film stability are invasive or show limited repeatability. Here we propose a new non-invasive fully automated approach to measure tear film thickness based on spectral domain optical coherence tomography and on an efficient delay estimator. Silicon wafer phantom were used to validate the thickness measurement. The technique was applied in vivo in healthy subjects. Series of tear film thickness maps were generated, allowing for the visualization of tear film dynamics. Our results ...

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    8. Blood flow velocity vector field reconstruction from dual-beam bidirectional Doppler OCT measurements in retinal veins

      Blood flow velocity vector field reconstruction from dual-beam bidirectional Doppler OCT measurements in retinal veins

      In this paper, we demonstrate the possibility to reconstruct the actual blood flow velocity vector field in retinal microvessels from dual-beam bidirectional Doppler optical coherence tomography measurements. First, for a better understanding of measured phase patterns, several flow situations were simulated on the basis of the known dual beam measurement geometry. We were able to extract the vector field parameters that determine the measured phase pattern, allowing for the development of an algorithm to reconstruct the velocity vector field from measured phase data. In a next step, measurements were performed at a straight vessel section and at a venous convergence ...

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    9. Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography

      Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography

      Purpose The aim of this study was to assess the effect of a single drop of hyaluronic acid on tear film thickness (TFT) in healthy subjects. Methods Sixteen healthy subjects (eight male/eight female) aged between 20 and 36 years were included in this randomized, double-masked placebo-controlled study. One eye received a single dose of hyaluronic acid (Olixia pure ® ; Croma Pharma, Korneuburg, Austria) eye drops, and the fellow eye received physiologic saline solution as placebo control. The study eye was chosen randomly. TFT as measured with a custom-built Fourier-domain optical coherence tomography (FD-OCT) system was the main outcome variable and ...

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    10. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

      Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

      A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique ...

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    11. Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

      Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

      We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray’s law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood’s velocity scaled linearly with the vessel diameter at higher diameters (> 60 µm), but showed a clear divergence from the linear dependence at ...

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    12. Measurement of Absolute Blood Flow Velocity and Blood Flow in the Human Retina by Dual-beam Bidirectional Doppler Fourier-Domain Optical Coherence Tomography

      Measurement of Absolute Blood Flow Velocity and Blood Flow in the Human Retina by Dual-beam Bidirectional Doppler Fourier-Domain Optical Coherence Tomography

      Purpose The present experiments were undertaken to evaluate the validity of absolute flow velocity measurements using a dual-beam bidirectional Doppler Fourier-domain optical coherence tomography (FD-OCT) system. Methods The flow velocities of diluted milk through a glass capillary were measured at 30 different preset velocities in the range of 0.9 to 39.3 mm/s by bidirectional Doppler FD-OCT. The flow through the capillary was controlled by two infusion pumps working in different flow ranges and based on different technical principles. In vivo the validity of the method for measuring blood flow in retinal vessels was tested at bifurcations. The ...

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    1-12 of 12
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    1. (10 articles) Medical University of Vienna
    2. (4 articles) Rainer A. Leitgeb
    3. (4 articles) Angelika Unterhuber
    4. (2 articles) Singapore Eye Research Institute
    5. (2 articles) Boston University
    6. (2 articles) David A. Boas
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    Measurement of Absolute Blood Flow Velocity and Blood Flow in the Human Retina by Dual-beam Bidirectional Doppler Fourier-Domain Optical Coherence Tomography Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography Blood flow velocity vector field reconstruction from dual-beam bidirectional Doppler OCT measurements in retinal veins In vivo tear film thickness measurement and tear film dynamics visualization using spectral domain optical coherence tomography Measurement of Retinal Vascular Caliber From Optical Coherence Tomography Phase Images Estimating Retinal Blood Flow Velocities by Optical Coherence Tomography Effect of different lubricant eye gels on tear film thickness as measured with ultrahigh-resolution optical coherence tomography Ultrahigh-resolution OCT imaging of the human cornea Comparative study between intravitreal ranibizumab and triamcinolone treatment of diabetic macular edema as regard to optical coherence tomography changes and visual acuity What’s New in Optical Coherence Tomography Angiography for Glaucoma (Book Chapter)