-
[show abstract]
[hide abstract]
ABSTRACT: PURPOSE: To image the retinal pigment epithelium (RPE) after macular laser and to monitor healing responses over time in vivo in patients with diabetic maculopathy using polarization-sensitive optical coherence tomography (OCT). DESIGN: Prospective, nonrandomized clinical trial. METHODS: In this single-center trial (Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria), 13 patients (13 eyes) underwent grid photocoagulation for diabetic maculopathy. Retinal healing processes were continuously followed over the course of 3 months. A polarization-sensitive OCT prototype was used, allowing detection and measurement of the RPE changes based on their specific polarization-scrambling qualities. RESULTS: After 1 day, the intraretinal photocoagulation lesions were sharply demarcated, whereas RPE changes were rather subtle. At 1 week, all lesions exhibited traction of the inner retinal layers toward the RPE and loss of photoreceptor cells. In tissue-sensitive polarization-sensitive OCT imaging, polarization-scrambling columns were found at the level of the RPE. During follow-up, different healing responses were seen in the polarization-scrambling RPE layer, ranging from hyperproliferation to focal atrophy. CONCLUSION: Because of the properties of the polarization state of backscattered light, polarization-sensitive OCT revealed specific morphologic changes in the RPE and outer retinal layers secondary to retinal laser treatment undetectable with intensity-based spectral-domain OCT. The increase in polarization-scrambling tissue over the course of 3 months indicates a more intense healing reaction and proliferation of RPE cells than previously characterized in rodent studies.
American journal of ophthalmology 02/2013; · 3.83 Impact Factor
-
Teresa Torzicky,
Sebastian Marschall,
Michael Pircher, Bernhard Baumann,
Marco Bonesi,
Stefan Zotter,
Erich Götzinger,
Wolfgang Trasischker,
Thomas Klein,
Wolfgang Wieser,
Benjamin Biedermann,
Robert Huber,
Peter Andersen,
Christoph K Hitzenberger
[show abstract]
[hide abstract]
ABSTRACT: We present a novel, high-speed, polarization-sensitive, optical coherence tomography set-up for retinal imaging operating at a central wavelength of 1060 nm which was tested for in vivo imaging in healthy human volunteers. We use the system in combination with a Fourier domain mode locked laser with active spectral shaping which enables the use of forward and backward sweep in order to double the imaging speed without a buffering stage. With this approach and with a custom designed data acquisition system, we show polarization-sensitive imaging with an A-scan rate of 350 kHz. The acquired three-dimensional data sets of healthy human volunteers show different polarization characteristics in the eye, such as depolarization in the retinal pigment epithelium and birefringence in retinal nerve fiber layer and sclera. The increased speed allows imaging of large volumes with reduced motion artifacts. Moreover, averaging several two-dimensional frames allows the generation of high-definition B-scans without the use of an eye-tracking system. The increased penetration depth of the system, which is caused by the longer probing beam wavelength, is beneficial for imaging choroidal and scleral structures and allows automated segmentation of these layers based on their polarization characteristics.
Journal of Biomedical Optics 02/2013; 18(2):26008. · 3.16 Impact Factor
-
Marco Bonesi,
Harald Sattmann,
Teresa Torzicky,
Stefan Zotter, Bernhard Baumann,
Michael Pircher,
Erich Götzinger,
Christoph Eigenwillig,
Wolfgang Wieser,
Robert Huber,
Christoph K Hitzenberger
[show abstract]
[hide abstract]
ABSTRACT: We recently reported on a new swept source polarization sensitive optical coherence tomography system and its application to skin imaging [Biomed. Opt. Express 3, 2987 (2012)]. In some of the tomographic images, two skin layers were labeled wrongly (interchanged). We present figures with corrected labeling.[This corrects the article on p. 2987 in vol. 3, PMID: 23162734.].
Biomedical Optics Express 02/2013; 4(2):241-244. · 2.33 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: PURPOSE: TO INVESTIGATE THE REPRODUCIBILITY OF AUTOMATED LESION SIZE DETECTION IN PATIENTS WITH GEOGRAPHIC ATROPHY (GA) USING POLARIZATION-SENSITIVE SPECTRAL DOMAIN-OCT (PS-OCT) AND TO COMPARE FINDINGS WITH SCANNING LASER OPHTHALMOSCOPY (SLO), FUNDUS AUTOFLUORESCENCE (FAF), AND INTENSITY BASED SD-OCT. METHODS: 29 eyes of 22 patients with GA were examined by PS-OCT, selectively identifying the retinal pigment epithelium (RPE). A novel segmentation algorithm was applied, automatically detecting and quantifying areas of RPE atrophy. The reproducibility of the algorithm was assessed and lesion sizes were correlated with manually delineated SLO, FAF and intensity based SD-OCT images to validate the clinical applicability of PS-OCT in GA evaluation. RESULTS: Mean GA lesion size of all patients was 5.28mm2 (SD:4.92) in PS-OCT. Mean variability of individual repeatability measurements was 0.83mm² (min:0.05, max:3.65). Mean coefficient of variation was 0.07 (min:0.01, max:0.19). Mean GA area in SLO (Spectralis OCT) was 5.15mm2 (SD:4.72) and 2.5% smaller than in PS-OCT (p=0.9, Pearson correlation coefficient=0.98, p<0.01). Mean GA area in intensity based SD-OCT pseudo SLO images (Cirrus OCT) was 5.14mm2 (SD:4.67) and 2.7% smaller than in PS-OCT (p=0.9, Pearson correlation coefficient=0.98, p<0.01). Mean GA area of all eyes measured 5.41mm2 (SD:4.75) in FAF, deviating by 2.4% from PS-OCT results (p=0.89, Pearson correlation coefficient=0.99, p<0.01). CONCLUSIONS: PS-OCT demonstrated high reproducibility of GA lesion size determination. Results correlated well with SLO, FAF and intensity based SD-OCT fundus imaging. PS-OCT may therefore be a valuable and specific imaging modality for automated GA lesion size determination in scientific studies and clinical practice.
Investigative ophthalmology & visual science 12/2012; · 3.43 Impact Factor
-
Stefan Zotter,
Michael Pircher,
Teresa Torzicky, Bernhard Baumann,
Hirofumi Yoshida,
Futoshi Hirose,
Philipp Roberts,
Markus Ritter,
Christopher Schütze,
Erich Götzinger,
Wolfgang Trasischker,
Clemens Vass,
Ursula Schmidt-Erfurth,
Christoph K Hitzenberger
[show abstract]
[hide abstract]
ABSTRACT: We present a novel spectral domain polarization sensitive OCT system (PS-OCT) that operates at an A-scan rate of 70 kHz and supports scan angles of up to 40° × 40°. The high-speed imaging allows the acquisition of up to 1024 × 250 A-scans per 3D scan, which, together with the large field of view, considerably increases the informative value of the images. To demonstrate the excellent performance of the new PS-OCT system, we imaged several healthy volunteers and patients with various diseases such as glaucoma, AMD, Stargardt's disease, and albinism. The results are compared with clinically established methods such as scanning laser polarimetry and autofluorescence.
Biomedical Optics Express 11/2012; 3(11):2720-32. · 2.33 Impact Factor
-
Marco Bonesi,
Harald Sattmann,
Teresa Torzicky,
Stefan Zotter, Bernhard Baumann,
Michael Pircher,
Erich Götzinger,
Christoph Eigenwillig,
Wolfgang Wieser,
Robert Huber,
Christoph K Hitzenberger
[show abstract]
[hide abstract]
ABSTRACT: We report on a new swept source polarization sensitive optical coherence tomography scan engine that is based on polarization maintaining (PM) fiber technology. The light source is a Fourier domain mode locked laser with a PM cavity that operates in the 1300 nm wavelength regime. It is equipped with a PM buffer stage that doubles the fundamental sweep frequency of 54.5 kHz. The fiberization allows coupling of the scan engine to different delivery probes. In a first demonstration, we use the system for imaging human skin at an A-scan rate of 109 kHz. The system illuminates the sample with circularly polarized light and measures reflectivity, retardation, optic axis orientation, and Stokes vectors simultaneously. Furthermore, depolarization can be quantified by calculating the degree of polarization uniformity (DOPU). The high scanning speed of the system enables dense sampling in both, the x- and y-direction, which provides the opportunity to use 3D evaluation windows for DOPU calculation. This improves the spatial resolution of DOPU images considerably.
Biomedical Optics Express 11/2012; 3(11):2987-3000. · 2.33 Impact Factor
-
Bernhard Baumann,
Stefan O Baumann,
Thomas Konegger,
Michael Pircher,
Erich Götzinger,
Ferdinand Schlanitz,
Christopher Schütze,
Harald Sattmann,
Marco Litschauer,
Ursula Schmidt-Erfurth,
Christoph K Hitzenberger
[show abstract]
[hide abstract]
ABSTRACT: Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT. In addition to imaging based on tissue reflectivity, PS-OCT also enables depth-resolved mapping of sample polarization properties such as phase-retardation, birefringent axis orientation, Stokes vectors, and degree of polarization uniformity (DOPU). In this study, PS-OCT was used to investigate the polarization properties of melanin. In-vitro measurements in samples with varying melanin concentrations revealed polarization scrambling, i.e. depolarization of backscattered light. Polarization scrambling in the PS-OCT images was more pronounced for higher melanin concentrations and correlated with the concentration of the melanin granules in the phantoms. Moreover, in-vivo PS-OCT was performed in the retinas of normal subjects and individuals with albinism. Unlike in the normal eye, polarization scrambling in the retinal pigment epithelium (RPE) was less pronounced or even not observable in PS-OCT images of albinos. These results indicate that the depolarizing appearance of pigmented structures like, for instance, the RPE is likely to be caused by the melanin granules contained in these cells.
Biomedical Optics Express 07/2012; 3(7):1670-83. · 2.33 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
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 IJT was suggested.
Polarization-sensitive spectral-domain optical coherence tomography together with SD-OCT identified characteristic patterns of IJT, used to classify eyes into three distinct groups. Group 1 (5 eyes) revealed discrete alterations in the inner retinal layers; group 2 (12 eyes) showed irregularities of the junction between the inner and outer photoreceptor segments with outer retinal atrophy but an intact RPE. Group 3 (5 eyes) revealed RPE irregularities and loss in addition to intraretinal alterations and photoreceptor abnormalities.
This study described characteristic morphologic changes in IJT based on PS-SD-OCT and SD-OCT. Morphologic changes were classified, possibly leading to an OCT-based grading scheme. The intensity images of SD-OCT verified intraretinal and photoreceptor irregularities in great detail, whereas PS-SD-OCT additionally showed RPE alterations.
Retina (Philadelphia, Pa.) 09/2011; 32(2):256-64. · 2.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present a high speed polarization sensitive spectral domain optical coherence tomography system based on polarization maintaining fibers and two high speed CMOS line scan cameras capable of retinal imaging with up to 128 k A-lines/s. This high imaging speed strongly reduces motion artifacts and therefore averaging of several B-scans is possible, which strongly reduces speckle noise and improves image quality. We present several methods for averaging retardation and optic axis orientation, the best one providing a 5 fold noise reduction. Furthermore, a novel scheme of calculating images of degree of polarization uniformity is presented. We quantitatively compare the noise reduction depending on the number of averaged frames and discuss the limits of frame numbers that can usefully be averaged.
Optics Express 07/2011; 19(15):14568-85. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: By combining dynamic mechanical testing with spectral-domain polarization-sensitive optical coherence tomography (SD-PS-OCT) performed at 1550 nm we are able to directly investigate for the first time changes within scattering technical materials during tensile and fracture tests. Spatially and temporally varying polarization patterns, due to defects and material inhomogeneities, were observed within bulk polymer samples and used to finally obtain--with the help of advanced image processing algorithms--quantitative maps of the evolving internal stress distribution. Furthermore, locally increased stress within fiber-reinforced composite materials was identified in situ with SD-PS-OCT to cause depolarizing sites of fiber-matrix debonding prior the onset of complete structural failure.
Optics Express 12/2010; 18(25):25712-25. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present a new ultra high resolution spectral domain polarization sensitive optical coherence tomography (PS-OCT) system based on polarization maintaining (PM) fibers. The method transfers the principles of our previous bulk optic PS-OCT systems to a fiberized setup. The phase shift between the orthogonal polarization states travelling in the two orthogonal modes of the PM fiber is compensated by software in post processing. Thereby, the main advantage of our bulk optics setups, i.e. the use of only a single input polarization state to simultaneously acquire reflectivity, retardation, optic axis orientation, and Stokes vector, is maintained. The use of a broadband light source of 110 nm bandwidth provides improved depth resolution and smaller speckle size. The latter is important for improved resolution of depolarization imaging. We demonstrate our instrument for high-resolution PS-OCT imaging of the healthy human retina.
Optics Express 12/2009; 17(25):22704-17. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Purpose. Spectral-domain optical coherence tomography (SD-OCT) provides new insights into the understanding of age-related macular degeneration (AMD) but limited information on the nature of hyperreflective tissue at the level of the retinal pigment epithelium. Therefore, polarization-sensitive (PS) SD-OCT was used to identify and characterize typical RPE findings in AMD. Methods. Forty-four eyes of 44 patients with AMD were included in 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). Imaging systems were used for comparative imaging. A PS-SD-OCT instrument was developed that was capable of recording intensity and polarization parameters simultaneously during a single scan. Results. In drusen, PS-SD-OCT identified a continuous RPE layer with focal elevations. Discrete RPE atrophy (RA) could be observed in two patients. In GA, the extension of the RA was significantly larger. Residual RPE islands could be detected within the atrophic zone. PS-SD-OCT identified multiple foci of RPE loss in patients with nAMD and allowed recognition of advanced RPE disease associated with choroidal neovascularization. Wide areas of RA containing residual spots of intact retinal pigment epithelium could be identified in fibrotic scars. Conclusions. PS-SD-OCT provided precise identification of retinal pigment epithelium in AMD. Recognition of these disease-specific RA patterns in dry and wet forms of AMD is of particular relevance to identify the status and progression of RPE disease and may help to better estimate the functional prognosis of AMD.
Investigative ophthalmology & visual science 09/2009; 51(4):2149-57. · 3.43 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Polarization sensitive optical coherence tomography (PS-OCT) allows for depth resolved imaging of polarization properties of retinal structures. Different layers in the retina can be distinguished not only based on their reflectivity but also due to their birefringent, depolarizing or polarization preserving character. In contrast to other structures in the posterior segment, the retinal pigment epithelium (RPE) is depolarizing, i.e., it scrambles the polarization state of light. A spectral domain (SD) PS-OCT system was used to record 3D data sets of the retina. The depolarizing effect of the RPE was analyzed by quantitative evaluation of the spatial depolarization distribution in the macula regions of healthy eyes. Depolarization in the RPE is most pronounced close to the center of the fovea and decreases with eccentricity.
Journal of Biophotonics 07/2009; 2(6-7):426-34. · 4.34 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present what we believe to be a novel approach to measuring optical path length differences with a precision of a few nanometers. The instrument is based on transverse scanning or en-face optical coherence tomography. Owing to the fast motion of the scanning beam over the sample, excellent phase stability in the transverse direction is achieved. Hence, phase changes caused by the varying optical path lengths within the sample arm occur with high frequency in the fast scanning direction. These changes are well separated from the rather slow phase changes introduced by jitter within the interferometer and can therefore be measured. The en-face imaging speed of the instrument is 40 fps (520 x 200 pixels). The measured precision of the method to detect small changes in optical path lengths was approximately 3 nm.
Optics Letters 07/2009; 34(12):1750-2. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper we present our improved transversal scanning OCT system that is capable of retinal imaging with cellular resolution. A fast axial eye tracking device was implemented into the system which practically eliminates eye motion artifacts in depth. Together with software based algorithms to correct for transverse eye motion 3D volumes of the human retina with greatly reduced motion artifacts and with isotropic resolution are presented. With this instrument long term changes of single human cone photoreceptors are observed.
06/2009;
-
[show abstract]
[hide abstract]
ABSTRACT: 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 and test their own data processing algorithms.
Optics Express 04/2009; 17(5):4151-65. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To analyze the physical origin of atypical scanning laser polarimetry (SLP) patterns. To compare polarization-sensitive optical coherence tomography (PS-OCT) scans to SLP images. To present a method to obtain pseudo-SLP images by PS-OCT that are free of atypical artifacts.
Forty-one eyes of healthy subjects, subjects with suspected glaucoma, and patients with glaucoma were imaged by SLP (GDx VCC) and a prototype spectral domain PS-OCT system. The PS-OCT system acquires three-dimensional (3D) datasets of intensity, retardation, and optic axis orientation simultaneously within 3 seconds. B-scans of intensity and retardation and en face maps of retinal nerve fiber layer (RNFL) retardation were derived from the 3D PS-OCT datasets. Results were compared with those obtained by SLP.
Twenty-two eyes showed atypical retardation patterns, and 19 eyes showed normal patterns. From the 22 atypical eyes, 15 showed atypical patterns in both imaging modalities, five were atypical only in SLP images, and two were atypical only in PS-OCT images. In most (15 of 22) atypical cases, an increased penetration of the probing beam into the birefringent sclera was identified as the source of atypical patterns. In such cases, the artifacts could be eliminated in PS-OCT images by depth segmentation and exclusion of scleral signals.
PS-OCT provides deeper insight into the contribution of different fundus layers to SLP images. Increased light penetration into the sclera can distort SLP retardation patterns of the RNFL.
Investigative ophthalmology & visual science 01/2009; 49(12):5366-72. · 3.43 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We 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 the RPE: its depolarizing, or polarization scrambling effect on backscattered light. Two different segmentation algorithms are presented and discussed: a simpler algorithm based on retardation data, and a more sophisticated algorithm based on local variations of the polarization state calculated from averaged Stokes vector elements. By using a state of the art spectral domain PS-OCT instrument, we demonstrate the method in healthy and diseased eyes.
Optics Express 11/2008; 16(21):16410-22. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We report on a new method for segmenting the retinal pigment epithelium (RPE) in polarization sensitive optical coherence tomography (PS-OCT) images of the human retina. Contrary to previous segmentation algorithms that were based on variations of backscattered intensity between individual layers, our method uses an intrinsic tissue property of the RPE: its depolarizing, or polarization scrambling effect on backscattered light. By using a state of the art spectral domain PS-OCT instrument, we demonstrate the method in healthy eyes and in eyes of patients with age related macular degeneration.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
02/2008;
-
[show abstract]
[hide abstract]
ABSTRACT: It has been shown that transversal scanning (or en-face) optical coherence tomography (TS-OCT) represents an imaging modality capable to record high isotropic resolution images of the human retina in vivo. However, axial eye motion still remains a challenging problem of this technique. In this paper we introduce a novel method to compensate for this eye motion. An auxiliary spectral domain partial coherence interferometer (SD-PCI) was integrated into an existing TS-OCT system and used to measure accurately the position of the cornea. A light source emitting at 1310nm was used in the additional interferometer which enabled a nearly loss free coupling of the two measurement beams via a dichroic mirror. The recorded corneal position was used to drive an additional voice coil translation stage in the reference arm of the TS-OCT system to correct for axial eye motion. Currently, the correction can be performed with an update rate of ~200Hz. The TS-OCT instrument is operated with a line scan rate of 4000 transversal lines per second which enables simultaneous SLO/OCT imaging at a frame rate of 40fps. 3D data of the human retina with isotropic high resolution, that was sufficient to visualize the human cone mosaic in vivo, is presented.
Optics Express 01/2008; 15(25):16922-32. · 3.59 Impact Factor
