All Articles from René M. Werkmeister -Optical Coherence Tomography News

Articles from René M. Werkmeister

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1. Quantification of intrinsic optical signals in the outer human retina using optical coherence tomography
  
  Explore The New York Academy of Sciences Dec 12 2021 Ophthalmology
  
  Intrinsic optical signals constitute a noninvasive biomarker promising the objective assessment of retinal photoreceptor function. We employed a commercial optical coherence tomography (OCT) system and an OCT signal model for evaluation of optical path length (OPL) changes in the temporal outer retina of five healthy subjects during light adaptation. Data were acquired at 30 time points, in ambient light and during long duration stimulation with white light, and analyzed, employing a signal model based on the sum of seven Gaussian curves corresponding to all relevant anatomical structures of the outer retina. During light stimulation, mean OPL between rod outer segment ...
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  Mentions: Medical University of Vienna
2. Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography
  
  Explore Wiley Online Library Dec 10 2021 Ophthalmology
  
  Purpose: To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer. Methods: Twenty-four healthy volunteers participated in this randomized, double-masked, cross-over study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusion density was calculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of ...
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  Mentions: Medical University of Vienna
3. Optical Coherence Tomography Angiography Monitors Cutaneous Wound Healing under Angiogenesis-Promoting Treatment in Diabetic and Non-Diabetic Mice
  
  Explore MDPI Open Access Journals Platform Mar 16 2021 Ophthalmology
  
  During wound healing, the rapid re-establishment of a functional microcirculation in the wounded tissue is of utmost importance. We applied optical coherence tomography (OCT) angiography to evaluate vascular remodeling in an excisional wound model in the pinnae of C57BL/6 and db/db mice receiving different proangiogenic topical treatments. Analysis of the high-resolution OCT angiograms, including the four quantitative parameters vessel density, vessel length, number of bifurcations, and vessel tortuosity, revealed changes of the microvasculature and allowed identification of the overlapping wound healing phases hemostasis, inflammation, proliferation, and remodeling. Angiograms acquired in the inflammatory phase in the first days showed ...
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4. Deep learning differentiates between healthy and diabetic mouse ears from optical coherence tomography angiography images
  
  Explore The New York Academy of Sciences Feb 28 2021
  
  We trained a deep learning algorithm to use skin optical coherence tomography (OCT) angiograms to differentiate between healthy and type 2 diabetic mice. OCT angiograms were acquired with a custom-built OCT system based on an akinetic swept laser at 1322 nm with a lateral resolution of ∼13 μm and using split-spectrum amplitude decorrelation. Our data set consisted of 24 stitched angiograms of the full ear, with a size of approximately 8.2 × 8.2 mm, evenly distributed between healthy and diabetic mice. The deep learning classification algorithm uses the ResNet v2 convolutional neural network architecture and was trained on small ...
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  Mentions: Medical University of Vienna
5. Plexus-Specific Effect of Flicker-Light Stimulation on the Retinal Microvasculature Assessed with Optical Coherence Tomography Angiography
  
  Explore American Physiological Society Journal Dec 6 2020 Ophthalmology
  
  In neural tissues, the coupling between neural activity and blood flow is a physiological key principle in blood flow regulation. We used optical coherence tomography angiography to investigate stimulus-evoked hemodynamic responses in different microvascular layers of the human retina. Twenty-two healthy subjects were included. Vessel density before and during light stimulation was measured using optical coherence tomography angiography and assessed for the superficial, intermediate and deep capillary plexus of the retinal circulation. Volumetric blood flow was measured using a custom-built Doppler optical coherence tomography system. Our results show that flicker stimulation induced a significant increase in the vessel density of ...
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6. The Association between Tear Film Thickness as Measured with OCT and Symptoms and Signs of Dry Eye Disease: A Pooled Analysis of 6 Clinical Trials
  
  Explore MDPI Open Access Journals Platform Dec 1 2020 Ophthalmology
  
  Purpose: To determine the association between tear film thickness (TFT) as measured with ultra-high resolution optical coherence tomography (UHR-OCT) and signs and symptoms of dry eye disease (DED). Methods: A total of 450 eyes from 225 patients with DED from six different randomized clinical trials were included in this pooled analysis. In all subjects, TFT was measured with a custom-built UHR-OCT system. Symptoms of DED were quantified using a standardized Ocular Surface Disease Index (OSD)I questionnaire and clinical signs including tear film break up time (TFBUT) and Schirmer I test were assessed. Associations of the average TFT with OSDI ...
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7. Approaches to quantify optical coherence tomography angiography metrics
  
  Explore Home Nov 29 2020
  
  Optical coherence tomography (OCT) has revolutionized the field of ophthalmology in the last three decades. As an OCT extension, OCT angiography (OCTA) utilizes a fast OCT system to detect motion contrast in ocular tissue and provides a three-dimensional representation of the ocular vasculature in a non-invasive, dye-free manner. The first OCT machine equipped with OCTA function was approved by U.S. Food and Drug Administration in 2016 and now it is widely applied in clinics. To date, numerous methods have been developed to aid OCTA interpretation and quantification. In this review, we focused on the workflow of OCTA-based interpretation, beginning ...
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  Mentions: FDA
8. Cutaneous optical coherence tomography for longitudinal volumetric assessment of intradermal volumes in a mouse model
  
  Explore Nature Publishing Group Mar 10 2020 Dermatology
  
  Clinical evaluation of skin lesions requires precise and reproducible technologies for their qualitative and quantitative assessment. In this study, we investigate the applicability of a custom-built dermatologic OCT system for longitudinal assessment of intradermal volumes in a mouse model. The OCT, based on an akinetic swept laser working at 1310 nm was employed for visualization and quantification of intradermal deposits of three different hyaluronic acid-based hydrogel formulations – one commercial and two test substances. Hydrogels were applied in 22 BALB/c mice, and measurements were performed over a six-month time period. All hydrogels increased in volume within the first weeks and ...
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  Mentions: Medical University of Vienna Singapore Eye Research Institute Nanyang Technological University
9. Deep learning segmentation for optical coherence tomography measurements of the lower tear meniscus
  
  Explore OSA | OSA Publishing Feb 26 2020 Ophthalmology
  
  The tear meniscus contains most of the tear fluid and therefore is a good indicator for the state of the tear film. Previously, we used a custom-built optical coherence tomography (OCT) system to study the lower tear meniscus by automatically segmenting the image data with a thresholding-based segmentation algorithm (TBSA). In this report, we investigate whether the results of this image segmentation algorithm are suitable to train a neural network in order to obtain similar or better segmentation results with shorter processing times. Considering the class imbalance problem, we compare two approaches, one directly segmenting the tear meniscus (DSA), the ...
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  Mentions: Duke University Medical University of Vienna Singapore Eye Research Institute
10. Comparison of optical coherence tomography and high frequency ultrasound imaging in mice for the assessment of skin morphology and intradermal volumes
  
  Explore Nature Publishing Group Sep 24 2019 Dermatology
  
  Optical coherence tomography (OCT) and high-frequency ultrasound (HFUS), two established imaging modalities in the field of dermatology, were evaluated and compared regarding their applicability for visualization of skin tissue morphology and quantification of murine intradermal structures. The accuracy and reproducibility of both methods were assessed ex vivo and in vivo using a standardized model for intradermal volumes based on injected soft tissue fillers. OCT revealed greater detail in skin morphology, allowing for detection of single layers due to the superior resolution. Volumetric data measured by OCT (7.9 ± 0.3 μl) and HFUS (7.7 ± 0.5 μl) were in ...
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  Mentions: Medical University of Vienna
11. Light-induced changes of the subretinal space of the temporal retina observed via optical coherence tomography
  
  Explore Nature Publishing Group Sep 24 2019 Ophthalmology
  
  Photoreceptor function is impaired in many retinal diseases like age-related macular degeneration. Currently, assessment of the photoreceptor function for the early diagnosis and monitoring of these diseases is either subjective, as in visual field testing, requires contact with the eye, like in electroretinography, or relies on research prototypes with acquisition speeds unattained by conventional imaging systems. We developed an objective, noncontact method to monitor photoreceptor function using a standard optical coherence tomography system. This method can be used with various white light sources for stimulation. The technique was applied in five volunteers and detected a decrease of volume of the ...
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  Mentions: Medical University of Vienna
12. Characterization of dry eye disease in a mouse model by optical coherence tomography and fluorescein staining
  
  Explore OSA | OSA Publishing Aug 31 2019 Ophthalmology
  
  A custom-built ultrahigh-resolution optical coherence tomography (UHR-OCT) system and fluorescein staining were employed for investigation of a scopolamine induced dry eye mouse model. Acquired data was used to evaluate common and complementary findings of the two modalities. Central corneal thickness as measured by UHR-OCT increased significantly over the study period of 24 hours, from 89.0 ± 3.57 µm to 92.2 ± 4.07 µm. Both techniques were able to show corneal lesions with a large range of severity. Localized fluorescein staining was detected in 5% and diffuse staining in 45% of cases where no epithelial damage was visible with ...
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  Mentions: Duke University Medical University of Vienna Singapore Eye Research Institute
13. Ultrahigh‐resolution anterior segment optical coherence tomography for analysis of corneal microarchitecture during wound healing
  
  Explore Wiley Online Library Feb 19 2019 Ophthalmology
  
  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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14. In Vivo Characterization of Spontaneous Retinal Neovascularization in the Mouse Eye by Multifunctional Optical Coherence Tomography
  
  Explore IOVS Journal Apr 26 2018
  
  Purpose : To investigate the early development of spontaneous retinal neovascularization in the murine retina by a multifunctional optical coherence tomography approach. To characterize involved tissue changes in vivo and describe structural and functional changes over time. Methods : A multifunctional optical coherence tomography (OCT) system providing 3-fold contrast comprising reflectivity, polarization sensitivity, and OCT angiography (OCTA) was utilized to image very-low-density lipoprotein receptor (VLDLR) knockout mice. Baseline measurements were acquired as early as postnatal day 14 and a follow-up of neovascularization development was performed until the age of 3 months. Control mice were imaged accordingly and a multiparametric image analysis was ...
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  Mentions: Medical University of Vienna
15. Ultrahigh-resolution OCT imaging of the human cornea
  
  Explore OSA | OSA Publishing Feb 22 2017 Ophthalmology
  
  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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  Mentions: Medical University of Vienna Singapore Eye Research Institute
16. Effect of different lubricant eye gels on tear film thickness as measured with ultrahigh-resolution optical coherence tomography
  
  Explore Wiley Online Library Dec 18 2016 Ophthalmology
  
  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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17. Measurement of Retinal Vascular Caliber From Optical Coherence Tomography Phase Images
  
  Explore IOVS Journal Jul 13 2016 Ophthalmology
  
  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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  Mentions: Medical University of Vienna
18. Total Retinal Blood Flow in a Nonhuman Primate Optic Nerve Transection Model Using Dual-Beam Bidirectional Doppler FD-OCT and Microsphere Method
  
  Explore IOVS Journal Apr 1 2016 Ophthalmology
  
  Purpose : We validated noninvasive Doppler-optical coherence tomography (OCT) blood flow measurements against the terminal microsphere method in a surgical induced optic nerve transection nonhuman primate model. Methods : In 6 nonhuman primates, total retinal blood flow (TRBF) was measured with a custom-built dual-beam bidirectional Doppler Fourier Domain (FD)-OCT. Peripapillary retinal nerve fiber layer thickness (RNFLT) was measured by Spectralis spectral-domain (SD)-OCT. Measurements were performed every 10 to 15 days before and after unilateral optic nerve transection (ONT) until RNFLT was reduced by more than 40% from baseline. Before the animals were killed, TRBF was measured using the microsphere technique ...
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  Mentions: Heidelberg Engineering Medical University of Vienna Devers Eye Institute
19. In vivo tear film thickness measurement and tear film dynamics visualization using spectral domain optical coherence tomography
  
  Explore OSA | OSA Publishing Aug 13 2015 Ophthalmology
  
  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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  Mentions: Medical University of Vienna
20. Blood flow velocity vector field reconstruction from dual-beam bidirectional Doppler OCT measurements in retinal veins
  
  Explore opticsinfobase.org Apr 6 2015
  
  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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  Mentions: Medical University of Vienna
21. Line-field parallel swept source MHz OCT for structural and functional retinal imaging
  
  Explore opticsinfobase.org Feb 19 2015
  
  We demonstrate three-dimensional structural and functional retinal imaging with line-field parallel swept source imaging (LPSI) at acquisition speeds of up to 1 MHz equivalent A-scan rate with sensitivity better than 93.5 dB at a central wavelength of 840 nm. The results demonstrate competitive sensitivity, speed, image contrast and penetration depth when compared to conventional point scanning OCT. LPSI allows high-speed retinal imaging of function and morphology with commercially available components. We further demonstrate a method that mitigates the effect of the lateral Gaussian intensity distribution across the line focus and demonstrate and discuss the feasibility of high-speed optical angiography ...
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  Mentions: Medical University of Vienna
22. Effect of hyaluronic acid on tear film thickness as assessed with ultra-high resolution optical coherence tomography
  
  Explore Wiley Online Library Jan 21 2015 Ophthalmology
  
  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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  Mentions: Medical University of Vienna
23. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging
  
  Explore SPIE | Journal Oct 18 2014
  
  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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  Mentions: Medical University of Vienna
24. Doppler Optical Coherence Tomography
  
  Explore ScienceDirect Apr 4 2014 Ophthalmology
  
  Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A ...
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  Mentions: Medical University of Vienna
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