The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform

Masahiro Yamanari - One of the best experts on this subject based on the ideXlab platform.

  • parallel detection of jones matrix elements in polarization sensitive optical coherence tomography
    Biomedical Optics Express, 2019
    Co-Authors: Masahiro Yamanari, Sato Uematsu, Kenji Ishihara, Yasushi Ikuno
    Abstract:

    The polarization properties of a sample can be characterized using a Jones matrix. To measure the Jones matrix without assumptions of the sample, two different incident states of polarization are usually used. This requirement often causes certain drawbacks in polarization-sensitive optical coherence tomography (PS-OCT), e.g., a decrease in the effective A-scan rate or axial depth range, if a multiplexing scheme is used. Because both the A-scan rate and axial depth range are important for clinical applications, including the imaging of an Anterior Eye Segment, a new PS-OCT method that does not have these drawbacks is desired. Here, we present a parallel-detection approach that maintains the same A-scan rate and axial measurement range as conventional OCT. The interferometer consists of fiber-optic components, most of which are polarization-maintaining components with fast-axis blocking free from polarization management. When a parallel detection is implemented using swept-source OCT (SS-OCT), synchronization between the A-scans and synchronization between the detection channels have critical effects on the Jones-matrix measurement. Because it is difficult to achieve perfect synchronization using only hardware, we developed a solution using a numerical correction with signals from a static mirror. Using the developed system, we demonstrate the imaging of an Anterior Eye Segment from the cornea to the back surface of the crystalline lens.

  • fiber based polarization sensitive oct for birefringence imaging of the Anterior Eye Segment
    Biomedical Optics Express, 2015
    Co-Authors: Masahiro Yamanari, Satoru Tsuda, Taiki Kokubun, Yukihiro Shiga, Kazuko Omodaka, Yu Yokoyama, Noriko Himori, Morin Ryu, Shiho Kunimatsusanuki, Hidetoshi Takahashi
    Abstract:

    We demonstrate a prototype system of polarization-sensitive optical coherence tomography (PS-OCT) designed for clinical studies of the Anterior Eye Segment imaging. The system can measure Jones matrices of the sample with depth-multiplexing of two orthogonal incident polarizations and polarization-sensitive detection. An optical clock is generated using a quadrature modulator and a logical circuit to double the clock frequency. Systematic artifacts in measured Jones matrices are theoretically analyzed and numerically compensated using signals at the surface of the sample. Local retardation images of filtering blebs after trabeculectomy show improved visualization of subconjunctival tissue, sclera, and scar tissue of the bleb wall in the Anterior Eye Segment.

  • birefringence measurement of cornea and Anterior Segment by office based polarization sensitive optical coherence tomography
    Biomedical Optics Express, 2011
    Co-Authors: Masahiro Yamanari, Shinichi Fukuda, Masahiro Miura, Takahiro Kiuchi, Yuichi Kaji, Tetsuro Oshika, Yoshiaki Yasuno
    Abstract:

    We present a case series of cornea and Anterior Segment disorders investigated by an office-based polarization-sensitive optical coherence tomography (PS-OCT). Blebs of glaucoma patients treated by trabeculectomy, and corneas of keratoconus and keratoplasty patients were measured by PS-OCT. Birefringence formations in trabeculectomy bleb were measured in 1 control Eye and 3 Eyes of trabeculectomy model rabbits. Polarization insensitive scattering OCT and the depth-resolved birefringence were measured simultaneously by PS-OCT. Abnormal birefringence was observed in keratoconus cases with advanced thinning and with a rupture of Descemet’s membrane. The graft-host interface of the keratoplasty case showed abnormal birefringence. The appearance of abnormal birefringence in the cornea was likely to be an indication of cross-linking of collagen fibrils. The measurement of rabbit showed abnormal birefringence in the scarring Eyes. Wide regions of strong birefringence were observed in the Eyes of trabeculectomy patients who had high intraocular pressure. Visualization of scarring in bleb by PS-OCT may be useful for the planning of secondary surgery. PS-OCT showed promising for the study and diagnosis diseases related to abnormal fibrous tissues of the cornea and Anterior Eye Segment.

  • tissue discrimination in Anterior Eye using three optical parameters obtained by polarization sensitive optical coherence tomography
    Optics Express, 2009
    Co-Authors: Arata Miyazawa, Masahiro Yamanari, Masahiro Miura, Keisuke Kawana, Shuichi Makita, Keiichi Iwaya, Hiroshi Goto, Yoshiaki Yasuno
    Abstract:

    We developed a tissue discrimination algorithm of polarization sensitive optical coherence tomography (PS-OCT) based on the optical properties of tissues. We calculated the three-dimensional (3D) feature vector from the parameters intensity, extinction coefficient, birefringence, which were obtained by PS-OCT. The tissue type of each pixel was determined according to the position of the feature vector in the 3D feature space. The algorithm was applied for discriminating tissues of the human Anterior Eye Segment. The conjunctiva, sclera, trabecular meshwork (TM), cornea, and uvea were well separated in the 3D feature space, and we observed them with good contrast. The TM line can be observed in the 3D discriminated volume, as observed by gonioscopy. We validated our method by applying our algorithm and histological data to porcine Eyes. A marker was injected into sub-Tenon’s space and the tissues that were Anterior to the marker and posterior to the marker were successfully Segmented by our algorithm.

  • investigation of post glaucoma surgery structures by three dimensional and polarization sensitive Anterior Eye Segment optical coherence tomography
    Optics Express, 2009
    Co-Authors: Yoshiaki Yasuno, Masahiro Yamanari, Tetsuro Oshika, Keisuke Kawana, Masahiro Miura
    Abstract:

    A sequential case series of post-glaucoma-surgery structures examined by three-dimensional corneal and Anterior Eye Segment optical coherence tomography (3D-CASOCT) and 3D polarization sensitive CASOCT (PS-CASOCT) is presented. A total of 5 patients who underwent glaucoma surgery were included in this study. Of these, 1, 1, and 3 patient underwent trabeculotomy, laser iridotomy, and trabeculectomy respectively. One patient each who had undergone trabeculotomy or laser iridotomy was examined using a prototype 3D-CASOCT. This prototype is based on swept-source OCT technology, uses a probe beam with a center wavelength of 1.31 microm, and has an axial resolution of 11.6 microm and a scanning speed of 20,000 A lines/s. All 3 patients who underwent trabeculectomy were examined by PS-CASOCT, which has similar specifications to those of 3DCASOCT, measures the depth-resolved birefringence of a specimen, and yields conventional OCT images. Detailed 3D visualization of the incision site of trabeculotomy and the ablation site of laser iridotomy was achieved using 3D-CASOCT. PS-CASOCT revealed, in addition to the structural details, the birefringent properties of the tissues of the trabeculectomy bleb. Some blebs showed abnormal birefringence in the conjunctiva and in a remnant fluid pool. This may indicate the existence of fibrosis in these regions. Both 3D-CASOCT and PS-CASOCT provide clinically significant information for the postoperative assessment of structures created during glaucoma surgery. Interactive 3D datasets of all cases are provided for interactive clinical review. Complex raw 3D OCT volumes are also provided as a reference dataset for the development of PS-OCT algorithms.

Yoshiaki Yasuno - One of the best experts on this subject based on the ideXlab platform.

  • birefringence measurement of cornea and Anterior Segment by office based polarization sensitive optical coherence tomography
    Biomedical Optics Express, 2011
    Co-Authors: Masahiro Yamanari, Shinichi Fukuda, Masahiro Miura, Takahiro Kiuchi, Yuichi Kaji, Tetsuro Oshika, Yoshiaki Yasuno
    Abstract:

    We present a case series of cornea and Anterior Segment disorders investigated by an office-based polarization-sensitive optical coherence tomography (PS-OCT). Blebs of glaucoma patients treated by trabeculectomy, and corneas of keratoconus and keratoplasty patients were measured by PS-OCT. Birefringence formations in trabeculectomy bleb were measured in 1 control Eye and 3 Eyes of trabeculectomy model rabbits. Polarization insensitive scattering OCT and the depth-resolved birefringence were measured simultaneously by PS-OCT. Abnormal birefringence was observed in keratoconus cases with advanced thinning and with a rupture of Descemet’s membrane. The graft-host interface of the keratoplasty case showed abnormal birefringence. The appearance of abnormal birefringence in the cornea was likely to be an indication of cross-linking of collagen fibrils. The measurement of rabbit showed abnormal birefringence in the scarring Eyes. Wide regions of strong birefringence were observed in the Eyes of trabeculectomy patients who had high intraocular pressure. Visualization of scarring in bleb by PS-OCT may be useful for the planning of secondary surgery. PS-OCT showed promising for the study and diagnosis diseases related to abnormal fibrous tissues of the cornea and Anterior Eye Segment.

  • tissue discrimination in Anterior Eye using three optical parameters obtained by polarization sensitive optical coherence tomography
    Optics Express, 2009
    Co-Authors: Arata Miyazawa, Masahiro Yamanari, Masahiro Miura, Keisuke Kawana, Shuichi Makita, Keiichi Iwaya, Hiroshi Goto, Yoshiaki Yasuno
    Abstract:

    We developed a tissue discrimination algorithm of polarization sensitive optical coherence tomography (PS-OCT) based on the optical properties of tissues. We calculated the three-dimensional (3D) feature vector from the parameters intensity, extinction coefficient, birefringence, which were obtained by PS-OCT. The tissue type of each pixel was determined according to the position of the feature vector in the 3D feature space. The algorithm was applied for discriminating tissues of the human Anterior Eye Segment. The conjunctiva, sclera, trabecular meshwork (TM), cornea, and uvea were well separated in the 3D feature space, and we observed them with good contrast. The TM line can be observed in the 3D discriminated volume, as observed by gonioscopy. We validated our method by applying our algorithm and histological data to porcine Eyes. A marker was injected into sub-Tenon’s space and the tissues that were Anterior to the marker and posterior to the marker were successfully Segmented by our algorithm.

  • investigation of post glaucoma surgery structures by three dimensional and polarization sensitive Anterior Eye Segment optical coherence tomography
    Optics Express, 2009
    Co-Authors: Yoshiaki Yasuno, Masahiro Yamanari, Tetsuro Oshika, Keisuke Kawana, Masahiro Miura
    Abstract:

    A sequential case series of post-glaucoma-surgery structures examined by three-dimensional corneal and Anterior Eye Segment optical coherence tomography (3D-CASOCT) and 3D polarization sensitive CASOCT (PS-CASOCT) is presented. A total of 5 patients who underwent glaucoma surgery were included in this study. Of these, 1, 1, and 3 patient underwent trabeculotomy, laser iridotomy, and trabeculectomy respectively. One patient each who had undergone trabeculotomy or laser iridotomy was examined using a prototype 3D-CASOCT. This prototype is based on swept-source OCT technology, uses a probe beam with a center wavelength of 1.31 microm, and has an axial resolution of 11.6 microm and a scanning speed of 20,000 A lines/s. All 3 patients who underwent trabeculectomy were examined by PS-CASOCT, which has similar specifications to those of 3DCASOCT, measures the depth-resolved birefringence of a specimen, and yields conventional OCT images. Detailed 3D visualization of the incision site of trabeculotomy and the ablation site of laser iridotomy was achieved using 3D-CASOCT. PS-CASOCT revealed, in addition to the structural details, the birefringent properties of the tissues of the trabeculectomy bleb. Some blebs showed abnormal birefringence in the conjunctiva and in a remnant fluid pool. This may indicate the existence of fibrosis in these regions. Both 3D-CASOCT and PS-CASOCT provide clinically significant information for the postoperative assessment of structures created during glaucoma surgery. Interactive 3D datasets of all cases are provided for interactive clinical review. Complex raw 3D OCT volumes are also provided as a reference dataset for the development of PS-OCT algorithms.

  • polarization sensitive swept source optical coherence tomography with continuous source polarization modulation
    Optics Express, 2008
    Co-Authors: Masahiro Yamanari, Shuichi Makita, Yoshiaki Yasuno
    Abstract:

    We present fiber-based polarization-sensitive swept-source optical coherence tomography (SS-OCT) based on continuous source polarization modulation. The light source is a frequency swept laser centered at 1.31 µm with a scanning rate of 20 kHz. The incident polarization is modulated by a resonant electro-optic modulator at 33.3 MHz, which is one-third of the data acquisition frequency. The zeroth- and first-order harmonic components of the OCT signals with respect to the polarization modulation frequency have the polarimetric information of the sample. By algebraic and matrix calculations of the signals, this system can measure the depth-resolved Jones matrices of the sample with a single wavelength scan. The phase fluctuations of the starting trigger of wavelength scan and the polarization modulation are cancelled by monitoring the OCT phase of a calibration mirror inserted into the sample arm. We demonstrate the potential of the system by the measurement of chicken breast muscle and the volumetric measurement of an in vivo human Anterior Eye Segment. The phase retardation image shows an additional contrast in the fibrous tissue such as the collagen fiber in the trabecular meshwork and sclera.

Masahiro Miura - One of the best experts on this subject based on the ideXlab platform.

  • birefringence measurement of cornea and Anterior Segment by office based polarization sensitive optical coherence tomography
    Biomedical Optics Express, 2011
    Co-Authors: Masahiro Yamanari, Shinichi Fukuda, Masahiro Miura, Takahiro Kiuchi, Yuichi Kaji, Tetsuro Oshika, Yoshiaki Yasuno
    Abstract:

    We present a case series of cornea and Anterior Segment disorders investigated by an office-based polarization-sensitive optical coherence tomography (PS-OCT). Blebs of glaucoma patients treated by trabeculectomy, and corneas of keratoconus and keratoplasty patients were measured by PS-OCT. Birefringence formations in trabeculectomy bleb were measured in 1 control Eye and 3 Eyes of trabeculectomy model rabbits. Polarization insensitive scattering OCT and the depth-resolved birefringence were measured simultaneously by PS-OCT. Abnormal birefringence was observed in keratoconus cases with advanced thinning and with a rupture of Descemet’s membrane. The graft-host interface of the keratoplasty case showed abnormal birefringence. The appearance of abnormal birefringence in the cornea was likely to be an indication of cross-linking of collagen fibrils. The measurement of rabbit showed abnormal birefringence in the scarring Eyes. Wide regions of strong birefringence were observed in the Eyes of trabeculectomy patients who had high intraocular pressure. Visualization of scarring in bleb by PS-OCT may be useful for the planning of secondary surgery. PS-OCT showed promising for the study and diagnosis diseases related to abnormal fibrous tissues of the cornea and Anterior Eye Segment.

  • tissue discrimination in Anterior Eye using three optical parameters obtained by polarization sensitive optical coherence tomography
    Optics Express, 2009
    Co-Authors: Arata Miyazawa, Masahiro Yamanari, Masahiro Miura, Keisuke Kawana, Shuichi Makita, Keiichi Iwaya, Hiroshi Goto, Yoshiaki Yasuno
    Abstract:

    We developed a tissue discrimination algorithm of polarization sensitive optical coherence tomography (PS-OCT) based on the optical properties of tissues. We calculated the three-dimensional (3D) feature vector from the parameters intensity, extinction coefficient, birefringence, which were obtained by PS-OCT. The tissue type of each pixel was determined according to the position of the feature vector in the 3D feature space. The algorithm was applied for discriminating tissues of the human Anterior Eye Segment. The conjunctiva, sclera, trabecular meshwork (TM), cornea, and uvea were well separated in the 3D feature space, and we observed them with good contrast. The TM line can be observed in the 3D discriminated volume, as observed by gonioscopy. We validated our method by applying our algorithm and histological data to porcine Eyes. A marker was injected into sub-Tenon’s space and the tissues that were Anterior to the marker and posterior to the marker were successfully Segmented by our algorithm.

  • investigation of post glaucoma surgery structures by three dimensional and polarization sensitive Anterior Eye Segment optical coherence tomography
    Optics Express, 2009
    Co-Authors: Yoshiaki Yasuno, Masahiro Yamanari, Tetsuro Oshika, Keisuke Kawana, Masahiro Miura
    Abstract:

    A sequential case series of post-glaucoma-surgery structures examined by three-dimensional corneal and Anterior Eye Segment optical coherence tomography (3D-CASOCT) and 3D polarization sensitive CASOCT (PS-CASOCT) is presented. A total of 5 patients who underwent glaucoma surgery were included in this study. Of these, 1, 1, and 3 patient underwent trabeculotomy, laser iridotomy, and trabeculectomy respectively. One patient each who had undergone trabeculotomy or laser iridotomy was examined using a prototype 3D-CASOCT. This prototype is based on swept-source OCT technology, uses a probe beam with a center wavelength of 1.31 microm, and has an axial resolution of 11.6 microm and a scanning speed of 20,000 A lines/s. All 3 patients who underwent trabeculectomy were examined by PS-CASOCT, which has similar specifications to those of 3DCASOCT, measures the depth-resolved birefringence of a specimen, and yields conventional OCT images. Detailed 3D visualization of the incision site of trabeculotomy and the ablation site of laser iridotomy was achieved using 3D-CASOCT. PS-CASOCT revealed, in addition to the structural details, the birefringent properties of the tissues of the trabeculectomy bleb. Some blebs showed abnormal birefringence in the conjunctiva and in a remnant fluid pool. This may indicate the existence of fibrosis in these regions. Both 3D-CASOCT and PS-CASOCT provide clinically significant information for the postoperative assessment of structures created during glaucoma surgery. Interactive 3D datasets of all cases are provided for interactive clinical review. Complex raw 3D OCT volumes are also provided as a reference dataset for the development of PS-OCT algorithms.

Roger Chiu - One of the best experts on this subject based on the ideXlab platform.

  • intra observer and inter observer repeatability of Anterior Eye Segment analysis system eas 1000 in Anterior chamber configuration
    Ophthalmic and Physiological Optics, 2002
    Co-Authors: Rufina Chan, Peter C K Pang, Roger Chiu
    Abstract:

    Background:  Anterior chamber configuration can be assessed via optical or ultrasonic techniques. Scheimpflug photography is a non-invasive method measuring the Anterior Segment. The Anterior Eye Segment analysis system, EAS-1000, utilises the Scheimpflug principle and was found to have good repeatability. Previous repeatability studies, however, have had limitations in their design. The current study investigated the intra-observer and interobserver repeatability of the EAS-1000. Methods:  Twenty-five healthy young subjects were recruited. The Anterior chamber angles in different quadrants were measured by two examiners for interobserver analysis. The first examiner repeated the measurement at another session for intra-observer analysis. The 95% limits of agreement and intra-class correlation coefficient (ICC) were calculated. The Anterior chamber depth was also measured and compared with ultrasound biometry. Results:  The Anterior chamber angle assessment demonstrated good intra-observer (ICC ranging from 0.77 to 0.90 for different quadrants) and interobserver (ICC ranging from 0.68 to 0.81 for different quadrants) repeatability. The 95% intra-observer limits of agreement were within ±5°. The 95% interobserver limits of agreement were within ±6°. There was no significant difference between male and female subjects or among angles at different quadrants. The Anterior chamber depth was found to be repeatable (ICC > 0.90) with 95% limits of agreement ±0.1 mm. The Anterior chamber depth was shallower than that obtained from ultrasound biometry. Conclusions:  The EAS-100 is a non-invasive instrument which is repeatable for measuring the Anterior chamber angle and depth. It provides quick results and is good for screening purposes. There is an under-estimation of Anterior chamber depth, as previously reported.

Christoph K Hitzenberger - One of the best experts on this subject based on the ideXlab platform.

  • extended in vivo Anterior Eye Segment imaging with full range complex spectral domain optical coherence tomography
    Journal of Biomedical Optics, 2009
    Co-Authors: Johannes Jungwirth, Bernhard Baumann, Michael Pircher, Erich Gotzinger, Christoph K Hitzenberger
    Abstract:

    We demonstrate the capability of full-range complex (FRC) spectral domain optical coherence tomography (SD-OCT) to image the Anterior Eye Segment from the cornea to the posterior surface of the lens. With an adapted spectrometer design, we developed a SD-OCT system with an extended normal (single half-space) depth range of 7 mm (in air). This OCT-intrinsic depth range was doubled with a FRC technique. We demonstrate the performance of our OCT system by imaging the whole Anterior Segment of a healthy human Eye in vivo.

  • biometric investigation of changes in the Anterior Eye Segment during accommodation
    SPIE milestone series, 2001
    Co-Authors: Wolfgang Drexler, Oliver Findl, Angela Baumgartner, Christoph K Hitzenberger, Adolf Friedrich Fercher
    Abstract:

    Non-invasive biometry of the Anterior structures of the human Eye can be performed with unprecedented precision of 8-10 μm and a resolution of ~9 μm by partial coherence interferometry, which has the potential to assess the effect of cycloplegia on the ocular components of the Anterior Eye Segment, to further improve the precision to 1-2 μm by the use of these agents and to quantify the amount of residual accommodations in different states of cycloplegia. In addition, the Anterior chamber depth, the thickness of the crystalline lens, their changes during accommodation, as well as the movement of the Anterior and posterior lens pole during accommodation can be quantified objectively and accurately to investigate the mechanism of accommodation.