1. Articles from Masahiro Yamanari

    1-24 of 58 1 2 3 »
    1. Retinal pigment epithelium melanin imaging using polarization-sensitive optical coherence tomography for patients with retinitis pigmentosa

      Retinal pigment epithelium melanin imaging using polarization-sensitive optical coherence tomography for patients with retinitis pigmentosa

      This study aimed to evaluate the distribution of retinal pigment epithelium (RPE) melanin in patients with retinitis pigmentosa (RP) using entropy measurements by custom-made polarization-sensitive optical coherence tomography (PS-OCT) images, and compare entropy with the intensity of short-wavelength (SW) and near-infrared (NIR) autofluorescence (AF). We retrospectively reviewed the retinal images, including PS-OCT, SW-AF, and NIR-AF of patients with RP who had a hyperautofluorescent ring on AF. A total of 12 eyes of 12 patients (8 women and 4 men; mean age: 37.9 years) were included. There was a strong positive correlation between entropy value and NIR-AF intensity (r = 0 ...

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    2. Optical coherence tomographic device comprising dual correction beams of different path lengths

      Optical coherence tomographic device comprising dual correction beams of different path lengths

      An optical coherence tomographic device may include a light source, a measurement light generator, a reference light generator, an interference light generator, an interference light detector, and a processor. The interference light detector may include a first and second detector that convert interference light to interference signals, a first signal processing unit that samples the interference signal from the first detector, and a second signal processing unit that samples the interference signal from the second detector. Each of the first and second signal processing units may sample the interference signal at a timing from outside. Light generated by the measurement ...

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    3. Visualization of Anterior Chamber Angle Structures With Scattering- and Polarization-Sensitive Anterior Segment Optical Coherence Tomography

      Visualization of Anterior Chamber Angle Structures With Scattering- and Polarization-Sensitive Anterior Segment Optical Coherence Tomography

      Purpose: The purpose of this study was to compare three optical coherence tomography (OCT) modalities in the observation of anterior chamber angle structures; trabecular meshwork (TM), Schlemm's canal (SC), and band of extracanalicular limbal lamina (BELL). Methods: Three OCT modalities were used: (1) 2 × 2 Jones-matrix scattering OCT (S-OCT) representing conventional intensity OCT, (2) polarization-diverse S-OCT that was calculated as summation of all elements of the Jones-matrix to eliminate the influence of artifacts caused by sample birefringence, and (3) polarization-sensitive OCT (PS-OCT) to assess depth-resolved phase retardation. Results: In a total of 97 eyes of 55 subjects, nasal and ...

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    4. Changes in entropy on polarized-sensitive optical coherence tomography images after therapeutic subthreshold micropulse laser for diabetic macular edema: A pilot study

      Changes in entropy on polarized-sensitive optical coherence tomography images after therapeutic subthreshold micropulse laser for diabetic macular edema: A pilot study

      Purpose To investigate the dynamics of the healing process after therapeutic subthreshold micropulse laser (SMPL) for diabetic macular edema (DME) using polarization-sensitive optical coherence tomography (PS-OCT). Methods Patients with treatment-native or previously-treated DME were prospectively imaged using PS-OCT at baseline, 1, 2, 3, and 6 months. The following outcomes were evaluated: changes in the entropy value per unit area (pixel 2 ) in the retinal pigment epithelium (RPE) on the B-scan image; changes in the entropy value in each stratified layer (retina, RPE, choroid) based on the ETDRS grid circle overlaid with en face entropy mapping, not only the whole ETDRS ...

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    5. Three-Dimensional Distribution Of Fundus Depolarization and Associating Factors Measured Using Polarization-Sensitive Optical Coherence Tomography

      Three-Dimensional Distribution Of Fundus Depolarization and Associating Factors Measured Using Polarization-Sensitive Optical Coherence Tomography

      Purpose : To investigate the three-dimensional distribution and associating demographic factors of depolarization, using polarization-sensitive optical coherence tomography (PS-OCT), to evaluate melanin pigmentation in the retinal pigment epithelium (RPE) and choroid in healthy eyes. Methods : In total, 39 unaffected healthy eyes of 39 subjects were examined using a PS-OCT clinical prototype. The degree of depolarization, expressed as the polarimetric entropy, was assessed in the RPE, the superficial and the total choroid layer, especially in the center, the inner, or the outer areas centered at the fovea. The values and their association with the demographic data were analyzed. Near-infrared fundus autofluorescence (NIRAF ...

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    6. Optical coherence tomographic device

      Optical coherence tomographic device

      An optical coherence tomographic device configured to acquire a tomographic image of a subject by using an optical interferometry is provided. The optical coherence tomographic device include: a detector configured to detect interference light acquired by the optical interferometry, and to output an interference signal of the interference light; and a processor configured to calculate von Neumann entropy of noise components by using the noise components and signal intensities of the interference signals corresponding to at least one interference light detected by the detector.

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    7. Melanin concentration and depolarization metrics measurement by polarization-sensitive optical coherence tomography

      Melanin concentration and depolarization metrics measurement by polarization-sensitive optical coherence tomography

      Imaging of melanin in the eye is important as the melanin is structurally associated with some ocular diseases, such as age-related macular degeneration. Although optical coherence tomography (OCT) cannot distinguish tissues containing the melanin from other tissues intrinsically, polarization-sensitive OCT (PS-OCT) can detect the melanin through spatial depolarization of the backscattered light from the melanin granules. Entropy is one of the depolarization metrics that can be used to detect malanin granules in PS-OCT and valuable quantitative information on ocular tissue abnormalities can be retrived by correlating entropy with the melanin concentration. In this study, we investigate a relationship between the ...

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    8. Imaging of a retinal pigment epithelium aperture using polarization-sensitive optical coherence tomography

      Imaging of a retinal pigment epithelium aperture using polarization-sensitive optical coherence tomography

      Purpose: To evaluate cases with a retinal pigment epithelium (RPE) aperture using polarization-sensitive optical coherence tomography (PS-OCT). Study design: Retrospective consecutive case series. Methods: A retrospective study that included three eyes (three patients) with RPE aperture and age-related macular degeneration (AMD) evaluated at the Macular Clinic in Tokyo University Hospital. A three-dimensional dataset of depolarization information was obtained with a clinical prototype of PS-OCT. Results: All patients were categorized as intermediate AMD. RPE apertures were identified with PS-OCT as discontinuities of depolarization in the RPE layer of the pigment epithelial detachment (PED). A nonuniform decrease of depolarization in the RPE ...

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    9. Usefulness of Polarization-sensitive Optical Coherence Tomography-derived Attenuation-coefficient Images to Visualize the Internal Structure of the Filtering Bleb

      Usefulness of Polarization-sensitive Optical Coherence Tomography-derived Attenuation-coefficient Images to Visualize the Internal Structure of the Filtering Bleb

      Purpose/Aim of the study Polarization-sensitive anterior-segmental optical coherence tomography (PS-OCT) is useful to evaluate the filtering blebs after trabeculectomy. However, the attenuation phenomenon of OCT signal disturbs the visibility of intra-bleb’s structure and distribution of birefringence; a specific parameter of PS-OCT. This study aimed to evaluate the effectiveness of the attenuation-coefficient image of the filtering blebs. Materials and methods This study included 25 eyes 6 months after TLE. The attenuation-coefficient image of blebs was calculated from OCT intensity signal information. The contrast level of the image (reflectivity of bleb’s surface wall/reflectivity of scleral flap) in both ...

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    10. Polarization-sensitive optical coherence tomography for estimating relative melanin content of autologous induced stem-cell derived retinal pigment epithelium

      Polarization-sensitive optical coherence tomography for estimating relative melanin content of autologous induced stem-cell derived retinal pigment epithelium

      Transplantation of autologous human induced pluripotent stem cell-derived retinal pigment epithelial (hiPSC-RPE) sheets is a promising therapy for age-related macular degeneration (AMD). As melanin content is a representative feature of healthy RPE, we used polarization-sensitive optical coherence tomography (PS-OCT) to estimate the relative melanin content of RPE in diseased and non-diseased area, and in human iPSC-RPE sheets in vitro and in vivo by evaluating the randomness of polarization (entropy). Two aged Japanese women, one with neovascular AMD that underwent transplantation of an autologous hiPSC-RPE cell sheet and another with binocular dry AMD, were selected for this study. Entropy value was ...

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    11. Parallel detection of Jones-matrix elements in polarization-sensitive optical coherence tomography

      Parallel detection of Jones-matrix elements in polarization-sensitive optical coherence tomography

      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 ...

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    12. Optical coherence tomography using polarization information

      Optical coherence tomography using polarization information

      The optical coherence tomography includes a processor, wherein the processor is configured to: vectorize the Jones matrix and then convert the vectorized Jones matrix into an expanded matrix; calculate at least an eigenvalue and at least an eigenvector of the expanded matrix by performing an eigenvalue decomposition to the expanded matrix; and estimate the polarization characteristic of the subject by using at least an eigenvalue and at least an eigenvector of the Jones matrix acquired based on the at least eigenvalue and the at least eigenvector of the expanded matrix.

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    13. Optical tomographic device capable of acquiring a plurality of tomographic images

      Optical tomographic device capable of acquiring a plurality of tomographic images

      Provided is an optical tomographic device for simultaneously acquiring a plurality of tomographic images at a same position in a subject without narrowing a depthwise measurement range. A measurement light generator generates at least two measurement lights with different optical path lengths, superimposes the at least two measurement lights, radiates the resultant light to a subject, and splits reflected light reflected from the subject into at least two reflected lights. A reference light generator generates at least two reference lights with different optical path lengths. An interfering light generator combines the at least two reflected lights and the at least ...

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    14. Estimation of Jones matrix, birefringence and entropy using Cloude-Pottier decomposition in polarization-sensitive optical coherence tomography

      Estimation of Jones matrix, birefringence and entropy using Cloude-Pottier decomposition in polarization-sensitive optical coherence tomography

      Estimation of polarimetric parameters has been a fundamental issue to assess biological tissues that have form birefringence or polarization scrambling in polarization-sensitive optical coherence tomography (PS-OCT). We present a mathematical framework to provide a maximum likelihood estimation of the target covariance matrix and its incoherent target decomposition to estimate a Jones matrix of a dominant scattering mechanism, called Cloude-Pottier decomposition, thereby deriving the phase retardation and the optic axis of the sample. In addition, we introduce entropy that shows the randomness of the polarization property. Underestimation of the entropy at a low sampling number is mitigated by asymptotic quasi maximum ...

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    15. Fiber-based polarization-sensitive OCT for birefringence imaging of the anterior eye segment

      Fiber-based polarization-sensitive OCT for birefringence imaging of the anterior eye segment

      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 ...

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    16. Scleral birefringence as measured by polarization-sensitive optical coherence tomography and ocular biometric parameters of human eyes in vivo

      Scleral birefringence as measured by polarization-sensitive optical coherence tomography and ocular biometric parameters of human eyes in vivo

      The relationship between scleral birefringence and biometric parameters of human eyes in vivo is investigated. Scleral birefringence near the limbus of 21 healthy human eyes was measured using polarization-sensitive optical coherence tomography. Spherical equivalent refractive error, axial eye length, and intraocular pressure (IOP) were measured in all subjects. IOP and scleral birefringence of human eyes in vivo was found to have statistically significant correlations ( r = −0.63, P = 0.002). The slope of linear regression was −2.4 × 10 −2 deg/μm/mmHg. Neither spherical equivalent refractive error nor axial eye length had significant correlations with scleral birefringence. To evaluate ...

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    17. Comparison of three-dimensional optical coherence tomography and combining a rotating Scheimpflug camera with a Placido topography system for forme fruste keratoconus diagnosis

      Comparison of three-dimensional optical coherence tomography and combining a rotating Scheimpflug camera with a Placido topography system for forme fruste keratoconus diagnosis

      Objective To evaluate the ability of parameters measured by three-dimensional (3D) corneal and anterior segment optical coherence tomography (CAS-OCT) and a rotating Scheimpflug camera combined with a Placido topography system (Scheimpflug camera with topography) to discriminate between normal eyes and forme fruste keratoconus. Methods Forty-eight eyes of 48 patients with keratoconus, 25 eyes of 25 patients with forme fruste keratoconus and 128 eyes of 128 normal subjects were evaluated. Anterior and posterior keratometric parameters (steep K, flat K, average K), elevation, topographic parameters, regular and irregular astigmatism (spherical, asymmetry, regular and higher-order astigmatism) and five pachymetric parameters (minimum, minimum–median ...

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    18. Comparison of three-dimensional optical coherence tomography and combining a rotating Scheimpflug camera with a Placido topography system for forme fruste keratoconus diagnosis

      Comparison of three-dimensional optical coherence tomography and combining a rotating Scheimpflug camera with a Placido topography system for forme fruste keratoconus diagnosis

      Objective To evaluate the ability of parameters measured by three-dimensional (3D) corneal and anterior segment optical coherence tomography (CAS-OCT) and a rotating Scheimpflug camera combined with a Placido topography system (Scheimpflug camera with topography) to discriminate between normal eyes and forme fruste keratoconus. Methods Forty-eight eyes of 48 patients with keratoconus, 25 eyes of 25 patients with forme fruste keratoconus and 128 eyes of 128 normal subjects were evaluated. Anterior and posterior keratometric parameters (steep K, flat K, average K), elevation, topographic parameters, regular and irregular astigmatism (spherical, asymmetry, regular and higher-order astigmatism) and five pachymetric parameters (minimum, minimum–median ...

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    19. Keratoconus diagnosis using anterior segment polarization-sensitive optical coherence tomography

      Keratoconus diagnosis using anterior segment polarization-sensitive optical coherence tomography

      Purpose: To investigate the tissue properties of keratoconic corneas and normal control in vivo by using polarization-sensitive optical coherence tomography (PS-OCT) and evaluate early keratoconus by the area under the receiver-operating curve and Mahalanobis distances analysis. Methods: Thirty one eyes of 20 patients with keratoconus, seven eyes of four patients with keratoconus suspect, and 25 eyes of 25 normal subjects were investigated by PS-OCT and corneal and anterior segment (CAS)-OCT. Average of en face phase retardation of the posterior surface of the cornea, curvature, videokeratographic parameters, regular and irregular astigmatism, pachymetry map, and elevation were measured. The AROC of ...

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    20. Optical Rheology of Porcine Sclera by Birefringence Imaging

      Optical Rheology of Porcine Sclera by Birefringence Imaging

      Purpose To investigate a relationship between birefringence and elasticity of porcine sclera ex vivo using polarization-sensitive optical coherence tomography (PS-OCT). Methods Elastic parameters and birefringence of 19 porcine eyes were measured. Four pieces of scleral strips which were parallel to the limbus, with a width of 4 mm, were dissected from the optic nerve head to the temporal side of each porcine eye. Birefringence of the sclera was measured with a prototype PS-OCT. The strain and force were measured with a uniaxial material tester as the sample was stretched with a speed of 1.8 mm/min after preconditioning. A ...

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    21. Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging

      Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging

      We present a fiber based multifunctional Jones matrix swept source optical coherence tomography (SS-OCT) system for Doppler and polarization imaging. Jones matrix measurement without using active components such as electro-optic modulators is realized by incident polarization multiplexing based on independent delay of two orthogonal polarization states and polarization diversity detection. In addition to polarization sensitivity, this system measures Doppler flow without extra hardware for phase stabilized SS-OCT detection. An eighth-wave plate was measured to demonstrate the polarization detection accuracy. The optic nerve head of a retina was measured in vivo. Detailed vasculature and birefringent structures were investigated simultaneously.

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    22. Office based multi-functional anterior eye segment optical coherence tomography

      Office based multi-functional anterior eye segment optical coherence tomography

      An office based Doppler and polarization sensitive swept-source optical coherence tomography (Doppler-PS-SS-OCT) was developed for diagnosis and evaluation of abnormalities of anterior eye segment in clinic. A healthy eye was measured in vivo by the Doppler PS-OCT. The results showed that the Doppler PS-OCT may have potential to identify blood vessels and discriminate fibrous tissues in abnormalities, such as scarring in bleb, and scleral inflammation.

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    23. Automated detection of chorio-scleral interface using polarization-sensitive optical coherence tomography

      Automated detection of chorio-scleral interface using polarization-sensitive optical coherence tomography

      A polarization sensitive optical coherence tomography based automated algorithm for segmentation of the chorio-scleral interface is presented. The algorithm employs a two-step segmentation approach. At first, local birefringence based segmentation with low precision is performed to roughly distinguish the choroid and sclera. Successively, a depth oriented slope fitting to phase retardation is applied in both the choroid and sclera. The interface is determined as the cross-point of the two phase retardation slope lines. The algorithm shows potential for functional, objective, and volumetric choroid thickness measurement

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    1-24 of 58 1 2 3 »
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    Tissue discrimination in anterior eye using three optical parameters obtainedby polarization sensitive optical coherence tomography Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging Automated phase retardation oriented segmentation of chorio-scleral interface by polarization sensitive optical coherence tomography New insights from non-invasive imaging: from prospection of skin photodamages to training with mobile application Short-sighted woman assumes debilitating headaches mean she needs new glasses but discovers she has multiple sclerosis Shedding light on the impact of microplastics on lentil seedling growth Comparison of radial peripapillary capillary density results of individuals with and without Helicobacter pylori infection Ai, Oct Operate in Tandem to Detect Plaque Erosion in the Heart Noninvasive, in vivo, characterization of cutaneous metastases using a novel multimodal RCM-OCT imaging device: A case-series Mimickers of punctate inner retinal toxoplasmosis on optical coherence tomography Measuring collagen injury depth for burn severity determination using polarization sensitive optical coherence tomography