1. Articles from Christian Ahlers

    1-19 of 19
    1. Morphologic Characteristics of Idiopathic Juxtafoveal Telangiectasia Using Spectral-Domain and Polarization-Sensitive Optical Coherence Tomography

      Morphologic Characteristics of Idiopathic Juxtafoveal Telangiectasia Using Spectral-Domain and Polarization-Sensitive Optical Coherence Tomography
      Purpose: Idiopathic juxtafoveal telangiectasia (IJT) is characteristically associated with pigmentary changes. Polarization-sensitive spectral-domain optical coherence tomography (PS-SD-OCT) enables imaging of the retinal pigment epithelium (RPE) and similar melanin-containing structures based on specific polarization properties. This study examined IJT with the latest-generation SD-OCT and PS-SD-OCT, identifying pathophysiologically relevant characteristics of the retinal layers and RPE. Methods: Twenty-two eyes of 12 patients with IJT were examined by PS-SD-OCT, with special focus on RPE detection and segmentation. Furthermore, SD-OCT technology (Cirrus, Spectralis, and 3D-OCT-1000) was applied. Characteristics of the retinal layers and RPE were evaluated. A classification system based on OCT characteristics of ...
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    2. Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension

      Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension

      Using a spectral domain OCT system, equipped with a broadband Ti:sapphire laser, we imaged the human retina with 5 µm x 1.3 µm transverse and axial resolution at acquisition rate of 100 kHz. Such imaging speed significantly reduces motion artifacts. Combined with the ultra-high resolution, this allows observing microscopic retinal details with high axial definition without the help of adaptive optics. In this work we apply our system to image the parafoveal capillary network. We demonstrate how already on the intensity level the parafoveal capillaries can be segmented by a simple structural high pass filtering algorithm. This data ...

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    3. Evaluation of Segmentation Procedures Using Spectral Domain Optical Coherence Tomography in Exudative Age-Related Macular Degeneration

      Evaluation of Segmentation Procedures Using Spectral Domain Optical Coherence Tomography in Exudative Age-Related Macular Degeneration
      Purpose: The purpose of this study was to evaluate standardized automated segmentation procedures of spectral domain optical coherence tomography (SD-OCT) in imaging of age-related macular degeneration. Methods: Twenty-nine eyes of 29 patients with neovascular age-related macular degeneration were included. Three groups were assigned, according to the predominant localization of extravasated fluid in the intra-, subretinal, and subretinal pigment epithelium (RPE) compartment. Automated segmentation procedures were evaluated in B scans of 512 × 128 × 1024 and 200 × 200 × 1024 scan patterns using SD-OCT (Cirrus). Alignment errors at the internal limiting membrane, actual RPE, and extrapolation of the physiologic RPE (RPE fit) were ...
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    4. Performance of Drusen Detection by Spectral-Domain Optical Coherence Tomography

      Performance of Drusen Detection by Spectral-Domain Optical Coherence Tomography
      Purpose. To evaluate the performance of automated analyses integrated in three spectral-domain optical coherence tomography (SD-OCT) devices to identify drusen in eyes with early (i.e., nonatrophic and nonneovascular) age-related macular degeneration (AMD). Methods. Twelve eyes of 12 AMD patients, classified as AREDS 2 and 3 and having a mean count of 113 drusen were examined with three clinical SD-OCT devices (Cirrus [Carl Zeiss Meditec, Dublin CA], 3DOCT-1000 [Topcon, Tokyo, Japan], and Spectralis [Heidelberg Engineering, GmbH, Heidelberg, Germany]) and five different scan patterns. After standard automated segmentation of the RPE was performed, every druse in each B-scan was identified and ...
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    5. Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography

      Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography
      We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the ...
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    6. Performance of OCT segmentation procedures to assess morphology and extension in geographic atrophy

      Performance of OCT segmentation procedures to assess morphology and extension in geographic atrophy
      Purpose: Investigating segmentation procedures and morphological findings in time domain (TD) and current spectral domain (SD) optical coherence tomography (OCT) devices in patients with geographic atrophy (GA).Methods: Fifty eyes of 46 patients with GA secondary to AMD and 15 control eyes were examined in this prospective noninterventional comparative case series. All patients underwent Stratus (model 3000), Cirrus (Carl Zeiss Meditec), Spectralis (Spectralis HRA+OCT; Heidelberg Engineering) and 3D-OCT-1000 (Topcon). Automated segmentation analyses were compared. An overlay of scanning laser ophthalmoscope (SLO) and three-dimensional retinal thickness (RT) maps were used to investigate whether areas of retinal thinning correspond to areas ...
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    7. Quantification of retinal lesions by polarization sensitive optical coherence tomography

      Quantification of retinal lesions by polarization sensitive optical coherence tomography
      Segmentation of retinal structures is an important step for quantitative diagnostic applications of optical coherence tomography (OCT) in ophthalmology. Contrary to previous segmentation algorithms that are based on intensity images, we use the tissue specific contrast provided by polarization sensitive (PS) OCT for segmentation of retinal layers and lesions. Our algorithms exploit the polarization scrambling property of the retinal pigment epithelium (RPE) in a first step to segment the RPE. The RPE is then used as a "backbone" to identify further structures like the normal RPE position (indicating Bruch's membrane) or the posterior tips of the photoreceptors. In a ...
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    8. Evaluation of anterior-segment inflammation and retinal thickness change following cataract surgery

      Purpose: To investigate the physiological retinal response to uneventful cataract surgery using conventional time-domain (TD-OCT) and current spectral-domain optical coherence tomography (SD-OCT) in combination with an assessment of the anterior chamber inflammatory reaction by laser flare/cell meter (LCFM).Methods: Thirty-four patients scheduled for cataract surgery were included in this prospective pilot study. Retinal parameters were examined according to a standardized examination procedure using TD-OCT (Stratus; Carl Zeiss Meditec, Dublin, California, USA) and SD-OCT (Cirrus; Carl Zeiss Meditec) devices. The inflammatory reaction of the anterior chamber was measured by LFCM (Kowa FC-1000, Kowa Co. Ltd, Tokyo, Japan). Examinations were carried ...
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    9. Imaging of the retinal pigment epithelium in age-related macular degeneration using polarization sensitive optical coherence tomography

      Purpose: Spectral-domain optical coherence tomography (SD-OCT) provided new insights into the understanding of age-related macular degeneration (AMD) but provides limited information on the nature of hyperreflective tissue at the level of the retinal pigment epithelium (RPE). Therefore, a polarization-sensitive SD-OCT (PS-SD-OCT) was used to identify and characterize typical RPE-findings in AMD. Methods: 44 eyes of 44 AMD-patients were included into this prospective case series representing the entire AMD-spectrum from drusen (n=11), geographic atrophy (GA, n=11), neovascular AMD (nAMD, n=11) to fibrotic scars (n=11). Cirrus (Carl-Zeiss-Meditec), Spectralis (Heidelberg) and 3D-OCT-1000 (Topcon) were used for comparative imaging. A ...
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    10. Automatic and manual segmentation of healthy retinas using high-definition optical coherence tomography

      Purpose: This study compared automatic- and manual segmentation modalities in the retina of healthy eyes using high-definition optical coherence tomography (HD-OCT).Methods: Twenty retinas in 20 healthy individuals were examined using an HD-OCT system (Carl Zeiss Meditec, Inc.). Three-dimensional imaging was performed with an axial resolution of 6 [mu]m at a maximum scanning speed of 25 000 A-scans/second. Volumes of 6 × 6 × 2 mm were scanned. Scans were analysed using a matlab-based algorithm and a manual segmentation software system (3D-Doctor). The volume values calculated by the two methods were compared.Results: Statistical analysis revealed a high correlation between ...
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    11. Alterations of intraretinal layers in acute central serous chorioretinopathy

      Purpose: Optical coherence tomography (OCT) is restricted by its low scanning speed and limited resolution. High-definition raster-scanning OCT (HD-OCT) was used to evaluate changes in retinal microstructure in patients with acute central serous chorioretinopathy (CSCR) and to find new morphological features.Methods: Eighteen patients with subretinal fluid accumulation caused by acute CSCR were imaged in a cross-sectional study design. High-speed frequency-domain HD-OCT was used to image an area of 6 × 6 mm in the macular retina. Three-dimensional analyses were performed using en-face imaging and section analysis of single HD-OCT scans.Results: Detailed information about fluid accumulation can be obtained in ...
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    12. Three-dimensional imaging of an optic disk pit using high resolution optical coherence tomography

      PURPOSE. To clarify the origin of the coexisting fluid in an optic disc pit case by using optical coherence tomography (OCT). METHODS. High resolution OCT (Cirrus™ prototype, Carl Zeiss Meditec) was used for image acquisition; three dimensional segmentation was performed using Food and Drug Administration–approved imaging software (3D-Doctor V4.0, Able software Corp., Lexington, MA) to demonstratethe structural changes of the optic nerve head and the retina. RESULTS. Using high resolution OCT, the authors demonstrated that this case of optic pit had a possible connection between the subretinal and the intraretinal space. CONCLUSIONS. The authors assume that the intraretinal ...
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    13. Three-dimensional polarization sensitive OCT imaging and interactive display of the human retina

      Three-dimensional polarization sensitive OCT imaging and interactive display of the human retina
      Polarization sensitive OCT has recently been shown to provide tissue specific contrast, enabling direct identification of retinal layers based on the intrinsic properties of their interaction with light. However, the capabilities of displaying and analyzing 3D datasets in scientific publications were rather limited. Within the framework of the Interactive Science Publishing project, we present new ways of displaying and analyzing 3D sets of various polarization parameters recorded in healthy and diseased human retinas. These datasets can be interactively explored by the reader. Furthermore, we provide data of the 3D distribution of backscattered Stokes vectors to allow the reader to develop ...
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    14. Quantitative measurement of the degree of polarization uniformity of light backscattered by retinal layers by polarization sensitive OCT

      We report on an extension of our previously presented polarization sensitive optical coherence tomography (PS-OCT) technique towards quantitative measurements and imaging of depolarization of light backscattered by the various layers of the human ocular fundus in vivo. We use a state of the art spec ... [Proc. SPIE 7168, 716814 (2009)] published Tue Feb 24, 2009.
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    15. Imaging the human retina in vivo with combined spectral-domain polarization-sensitive optical coherence tomography and scanning laser ophthalmoscopy

      Polarization-sensitive (PS) optical coherence tomography (OCT) allows for depth-resolved measurement of light polarizing properties of different layers in the human retina. Since their inherent polarizing properties are different, the retinal structures can be identified using PS-OCT. We present an ... [Proc. SPIE 7163, 71630N (2009)] published Wed Feb 18, 2009.
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    16. Identification of optical density ratios in subretinal fluid as a clinically relevant biomarker in exudative macular disease

      Purpose: To investigate the potential role of optical density ratios (ODR) obtained from subretinal fluid analysis in exudative macular disease and to identify the predictive role of ODR under therapy in comparison to conventional morphometric measurements (CMM). Methods: Fifteen patients with neovascular age-related macular degeneration (nAMD) and 15 patients with acute central serous chorioretinopathy (CSC) were included into this prospective comparative and interventional case series. High-definition optical coherence tomography (SD-OCT) was performed according to a standardized protocol. NAMD patients received a standard treatment consisting of 3 monthly doses of intravitreal ranibizumab. Best-corrected visual acuity (BCVA) was assessed at baseline, week ...
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    17. Three-dimensional angiographic imaging of leakage in branch retinal vein occlusion

      Purpose: Optical coherence tomography (OCT) is used to image branch retinal vein occlusion (BRVO) but lacks information about leakage dynamics and perfusion status. Topographical angiography (TAG) is capable of providing this information and has been described previously in age-related macular degeneration. This study evaluates TAG in BRVO.Methods: We included 56 eyes of 40 consecutive patients with BRVO and a reduction in central vision. Two groups were established based on whether argon laser coagulation was performed or not. A standardized follow-up was performed. The chorioretinal fluorescence pattern was reconstructed following TAG. Quantitative measurements were also performed.Results: TAG performed from ...
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    18. Retinal pigment epithelium segmentation by polarization sensitive optical coherence tomography

      Retinal pigment epithelium segmentation by polarization sensitive optical coherence tomography
      Erich Götzinger, Michael Pircher, Wolfgang Geitzenauer, Christian Ahlers, Bernhard Baumann, Stephan Michels, Ursula Schmidt-Erfurth, Christoph K. HitzenbergerWe present a new method for identifying and segmenting the retinal pigment epithelium (RPE) in polarization sensitive optical coherence tomography (PS-OCT) images of the human retina. Contrary to previous, intensity based segmentation algorithms, our method uses an intrinsic tissue property of ... [Opt. Express 16, 16410-16422 (2008)]
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    1-19 of 19
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    1. (19 articles) Medical University of Vienna
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    Retinal pigment epithelium segmentation by polarization sensitive optical coherence tomography Quantitative assessment of retinal disorders using polarization-sensitive optical coherence tomography Performance of OCT segmentation procedures to assess morphology and extension in geographic atrophy Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography Performance of Drusen Detection by Spectral-Domain Optical Coherence Tomography Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension Morphologic Characteristics of Idiopathic Juxtafoveal Telangiectasia Using Spectral-Domain and Polarization-Sensitive Optical Coherence Tomography AI-Assisted In Situ Detection of Human Glioma Infiltration Using a Novel Computational Method for Optical Coherence Tomography Motorized capsule for shadow-free OCT imaging and synchronous beam control Notal Vision Diagnostic Clinic reports completion of 6 million ForeseeHome AMD home-monitoring tests Monitoring retinal responses to acute intraocular pressure elevation in rats with visible light optical coherence tomography Optical Coherence Tomography-Angiography of Different Choroidal Neovascularization Subtypes in Wet Age-related Macular Degeneration