1. Articles from Masahiro Akiba

    1-24 of 42 1 2 »
    1. Sensorless astigmatism correction using a variable cross-cylinder for high lateral resolution optical coherence tomography in a human retina

      Sensorless astigmatism correction using a variable cross-cylinder for high lateral resolution optical coherence tomography in a human retina

      High lateral resolution ( ∼ 5 µ m ∼5µm ) optical coherence tomography (OCT) that employs a variable cross-cylinder (VCC) to compensate for astigmatism is presented for visualizing minute structures of the human retina. The VCC and its sensorless optimization process enable ocular astigmatism correction of up to − 5.0 −5.0 diopter within a few seconds. VCC correction has been proven to increase the signal-to-noise ratio and lateral resolution using a model eye. This process is also validated using the human eye by visualizing the capillary network and human cone mosaic. The proposed method is applicable to existing OCT, making high lateral ...

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    2. Ophthalmologic image display device and ophthalmologic imaging device

      Ophthalmologic image display device and ophthalmologic imaging device

      A storage device of an ophthalmologic image display device of an embodiment stores a three dimensional data set acquired by scanning a subject's eye using OCT. An image processor forms, based on the three dimensional data set, a B-mode image, front images, and composite front image obtained from the front images. A display controller displays the B-mode image, front images and composite front image in a predetermined layout. The display controller displays distinguishment color information for distinguishment between the front images by colors and slice area information that indicates a partial region of the B-mode image corresponding to a ...

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    3. Speckle reduction in optical coherence tomography images

      Speckle reduction in optical coherence tomography images

      An optical coherence tomography (OCT) image composed of a plurality of A-scans of a structure is analyzed by defining, for each A-scan, a set of neighboring A-scans surrounding the A-slices scan. Following an optional de-noising step, the neighboring A-scans are aligned in the imaging direction, then a matrix X is formed from the aligned A-scans, and matrix completion is performed to obtain a reduced speckle noise image.

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    4. Fundus analysis apparatus and fundus observation apparatus

      Fundus analysis apparatus and fundus observation apparatus

      A fundus analysis apparatus includes a storage, an area setting unit, and a morphological information generating unit. The storage is configured to store OCT information acquired by applying optical coherence tomography to the fundus of an eye. The area setting unit is configured to set a front area corresponding to a front surface of the lamina cribrosa and a rear area corresponding to a rear surface of the lamina cribrosa in the OCT information. The morphological information generating unit is configured to generate morphological information indicating the morphology of the lamina cribrosa based on at least the front area and ...

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    5. Assessment of the deformation of the outer nuclear layer in the Epiretinal membrane using spectral-domain optical coherence tomography

      Assessment of the deformation of the outer nuclear layer in the Epiretinal membrane using spectral-domain optical coherence tomography

      Background: We aimed to investigate the deformation of the outer nuclear layer using optical coherence tomography in patients with epiretinal membrane (ERM) and its relationship with metamorphopsia. Methods: Thirty-nine eyes from 39 patients with ERM were included in the study. Patients with the subtypes of pseudo macula hole and lamellar hole were excluded. Twenty-one fellow eyes without macular disease were included as normal controls. Forty-nine B-scan images were obtained in the range of 20 degrees around the macula using SD-OCT. The outer nuclear layer (ONL) was evaluated as a three-dimensional image (3D-ONL) reconstructed using the distance between the ONL and ...

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    6. Retinal Arteriole Pulse Waveform Analysis Using a Fully-Automated Doppler Optical Coherence Tomography Flowmeter: a Pilot Study

      Retinal Arteriole Pulse Waveform Analysis Using a Fully-Automated Doppler Optical Coherence Tomography Flowmeter: a Pilot Study

      Purpose : To evaluate the repeatability and reproducibility of the measurement of retinal arteriole pulse waveforms using a novel fully-automated Doppler optical coherence tomography (DOCT) flowmeter in healthy subjects. Methods : Twenty eyes of 20 healthy subjects were included to test the intrasession repeatability of pulse waveform analysis. DOCT measurements were performed based on a newly developed instantaneous Doppler angle measurement method. Upstroke time (UT), which is the time from the minimum to the maximum retinal blood velocity, and the resistance index (RI) of the retinal arteriole pulse waveform were measured. Coefficients of variation (CVs) and intraclass correlation coefficients (ICCs) were calculated ...

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    7. Glaucoma Diagnosis with Machine Learning Based on Optical Coherence Tomography and Color Fundus Image

      Glaucoma Diagnosis with Machine Learning Based on Optical Coherence Tomography and Color Fundus Image

      This study aimed to develop a machine learning-based algorithm for glaucoma diagnosis in patients with open-angle glaucoma, based on three-dimensional optical coherence tomography (OCT) data and color fundus images. In this study, 208 glaucomatous and 149 healthy eyes were enrolled, and color fundus images and volumetric OCT data from the optic disc and macular area of these eyes were captured with a spectral-domain OCT (3D OCT-2000, Topcon). Thickness and deviation maps were created with a segmentation algorithm. Transfer learning of convolutional neural network (CNN) was used with the following types of input images: (1) fundus image of optic disc in ...

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    8. Reducing speckle noise in optical coherence tomography images

      Reducing speckle noise in optical coherence tomography images

      A method and system are proposed to obtain a reduced speckle noise image of a subject from optical coherence tomography (OCT) image data of the subject. The cross sectional images each comprise a plurality of scan lines obtained by measuring the time delay of light reflected, in a depth direction, from optical interfaces within the subject. The method comprises two aligning steps. First the cross sectional images are aligned, then image patches of the aligned cross sectional images are aligned to form a set of aligned patches. An image matrix is then formed from the aligned patches; and matrix completion ...

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    9. Pilot study for three-dimensional assessment of laminar pore structure in patients with glaucoma, as measured with swept source optical coherence tomography

      Pilot study for three-dimensional assessment of laminar pore structure in patients with glaucoma, as measured with swept source optical coherence tomography

      Purpose To develop a method to quantify, based on swept-source optical coherence tomography (OCT), the 3D structure of the laminar pores in patients with glaucoma. Methods This retrospective study examined 160 laminar pores from 8 eyes of 8 cases: 4 normal subjects and 4 open-angle glaucoma (OAG) patients. We reconstructed 3D volume data for a 3 x 3 mm disc, using a method similar to OCT angiography, and segmented the structure of the lamina cribrosa. Then, we manually segmented each laminar pore in sequential C-scan images (>90 slices at 2.6-micron intervals) with VCAT5 (RIKEN, Japan). We compared the control ...

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    10. Retinal blood flow reduction after panretinal photocoagulation in Type 2 diabetes mellitus: Doppler optical coherence tomography flowmeter pilot study

      Retinal blood flow reduction after panretinal photocoagulation in Type 2 diabetes mellitus: Doppler optical coherence tomography flowmeter pilot study

      To use a Doppler optical coherence tomography (DOCT) flowmeter to investigate segmental retinal blood flow (RBF) and sum of the segmental RBFs (SRBF) changes after panretinal photocoagulation (PRP) was used to treat type 2 diabetes mellitus with severe diabetic retinopathy (DR). Data from five patients with proliferative DR (PDR) (mean age 51.9 ± 10.5 years) was analyzed. The vessel diameter (D), average velocity (V), and retinal blood flow (RBF) in veins were measured using a DOCT flowmeter before and four weeks after PRP. Segmental RBF from inferotemporal (IT), superotemporal (ST), inferonasal (IN), and superonasal (SN) veins were measured, and ...

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    11. IMPROVED DETECTION AND DIAGNOSIS OF POLYPOIDAL CHOROIDAL VASCULOPATHY USING A COMBINATION OF OPTICAL COHERENCE TOMOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

      IMPROVED DETECTION AND DIAGNOSIS OF POLYPOIDAL CHOROIDAL VASCULOPATHY USING A COMBINATION OF OPTICAL COHERENCE TOMOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

      Purpose: To assess the ability of optical coherence tomography (OCT) alone and in combination with OCT angiography (OCTA) to differentiate polypoidal choroidal vasculopathy (PCV) from neovascular age-related macular degeneration , as compared to fluorescein angiography and indocyanine green angiography. Methods: This is a cross-sectional study. All participants had a standardized history, clinical examination including measurement of best-corrected visual acuity, slit-lamp biomicroscopy, and indirect fundus examination, and underwent standardized imaging (color photography, fluorescein and indocyanine green angiography, OCT, and OCTA) after predefined protocols. We used a 2-step approach (Step 1: spectral domain OCT; Step 2: addition of OCTA) combining structural OCT and ...

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    12. Classification of optic disc shape in glaucoma using machine learning based on quantified ocular parameters

      Classification of optic disc shape in glaucoma using machine learning based on quantified ocular parameters

      Purpose This study aimed to develop a machine learning-based algorithm for objective classification of the optic disc in patients with open-angle glaucoma (OAG), using quantitative parameters obtained from ophthalmic examination instruments. Methods This study enrolled 163 eyes of 105 OAG patients (age: 62.3 ± 12.6, mean deviation of Humphrey field analyzer: -8.9 ± 7.5 dB). The eyes were classified into Nicolela’s 4 optic disc types by 3 glaucoma specialists. Randomly, 114 eyes were selected for training data and 49 for test data. A neural network (NN) was trained with the training data and evaluated with the test ...

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    13. Evaluation of retinal nerve fiber layer defect using wide-field en-face swept-source OCT images by applying the inner limiting membrane flattening

      Evaluation of retinal nerve fiber layer defect using wide-field en-face swept-source OCT images by applying the inner limiting membrane flattening

      Purpose The assessment of retinal nerve fiber layer defects (RNFLDs) is a useful part of glaucoma care. Here, we obtained en-face images of retinal layers below the inner limiting membrane (ILM) with swept source-optical coherence tomography (SS-OCT), and measured RNFLD angle with new software. Methods This study included 105 eyes of 105 normal tension glaucoma (NTG) patients (age, 59.8 ± 13.2). Exclusion criteria were best-corrected visual acuity < 0.5, axial length > 28 mm, nonglaucoma ocular disease, and systemic disease affecting the visual field. We obtained 12 x 9 mm 3D volume scans centered on the macula with SS-OCT (DRI ...

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    14. Repeatability and Reproducibility of Retinal Blood Flow Measurement Using a Doppler Optical Coherence Tomography Flowmeter in Healthy Subjects

      Repeatability and Reproducibility of Retinal Blood Flow Measurement Using a Doppler Optical Coherence Tomography Flowmeter in Healthy Subjects

      Purpose : To evaluate the repeatability and reproducibility of retinal blood flow (RBF) measurements in humans by using new auto-alignment and measurement software in a commercially available Doppler optical coherence tomography (DOCT) system. Methods : The DOCT flowmeter assessed the intrasession repeatability and the intersession and interobserver reproducibility of the RBF measurements. For intrasession repeatability, the coefficients of variation (CVs) of five repeated RBF measurements were calculated at the retinal arteries and veins in 20 normal eyes of 20 healthy volunteers. For intersession reproducibility, two sets of three measurements obtained by one observer on 2 different days were compared. For interobserver reproducibility ...

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    15. Evaluation of Retinal Circulation Using Segmental-Scanning Doppler Optical Coherence Tomography in Anesthetized Cats

      Evaluation of Retinal Circulation Using Segmental-Scanning Doppler Optical Coherence Tomography in Anesthetized Cats

      Purpose : To study retinal blood flow (RBF) measurement reproducibility using segmental-scanning Doppler optical coherence tomography (DOCT) in vitro in glass capillaries and in vivo in anesthetized cats. Methods : As a preliminary study, the flow rates of human blood through glass capillaries were changed by using an infusion pump and measured at 13 preset velocities by DOCT. For in vivo measurement, the cats were anesthetized using sevoflurane. The flow in the parent vessel was compared with the sum of the flow values in the two daughter vessels. The RBF was measured using two different instruments: bidirectional laser Doppler velocimetry (LDV) and ...

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    16. Speckle Reduction in 3D Optical Coherence Tomography of Retina by A-Scan Reconstruction

      Speckle Reduction in 3D Optical Coherence Tomography of Retina by A-Scan Reconstruction

      Optical coherence tomography (OCT) is a micrometer-scale, cross-sectional imaging modality for biological tissue. It has been widely used for retinal imaging in ophthalmology. Speckle noise is problematic in OCT. A raw OCT image/volume usually has very poor image quality due to speckle noise, which often obscures the retinal structures. Overlapping scan is often used for speckle reduction in a 2D line-scan. However, it leads to an increase of the data acquisition time. Therefore, it is unpractical in 3D scan as it requires a much longer data acquisition time. In this paper, we propose a new method for speckle reduction ...

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    17. Clinical Factors Associated with Lamina Cribrosa Thickness in Patients with Glaucoma, as Measured with Swept Source Optical Coherence Tomography

      Clinical Factors Associated with Lamina Cribrosa Thickness in Patients with Glaucoma, as Measured with Swept Source Optical Coherence Tomography

      Purpose To investigate the influence of various risk factors on thinning of the lamina cribrosa (LC), as measured with swept-source optical coherence tomography (SS-OCT; Topcon). Methods This retrospective study comprised 150 eyes of 150 patients: 22 normal subjects, 28 preperimetric glaucoma (PPG) patients, and 100 open-angle glaucoma patients. Average LC thickness was determined in a 3 x 3 mm cube scan of the optic disc, over which a 4 x 4 grid of 16 points was superimposed (interpoint distance: 175 μm), centered on the circular Bruch’s membrane opening. The borders of the LC were defined as the visible limits ...

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    18. Analysis of Peripapillary Geometric Characters in High Myopia Using Swept-Source Optical Coherence Tomography

      Analysis of Peripapillary Geometric Characters in High Myopia Using Swept-Source Optical Coherence Tomography

      Purpose : We measured the three-dimensional geometric profile around the optic nerve head (ONH) using swept-source optical coherence tomography (SS-OCT) in highly myopic eyes. Methods : We studied 114 highly myopic eyes (<−6.0 diopters [D]) of 114 patients without glaucoma. Eyes were examined using the prototype SS-OCT. The retinal pigment epithelium (RPE) and chorioscleral interface were traced, and the mean y -axis coordinates of 24 sectors were calculated in circular peripapillary (3.4-mm diameter) images. The peripapillary tilting index (PTI) was calculated by subtracting the mean y -axis coordinate of the RPE in a sector from the mean of all sectors ...

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    19. 3D Evaluation of the Lamina Cribrosa with Swept-Source Optical Coherence Tomography in Normal Tension Glaucoma

      3D Evaluation of the Lamina Cribrosa with Swept-Source Optical Coherence Tomography in Normal Tension Glaucoma

      Purpose Although the lamina cribrosa (LC) is the primary site of axonal damage in glaucoma, adequate methods to image and measure it are currently lacking. Here, we describe a noninvasive, in vivo method of evaluating the LC, based on swept-source optical coherence tomography (SS-OCT), and determine this method’s ability to quantify LC thickness. Methods This study comprised 54 eyes, including normal (n = 18), preperimetric glaucoma (PPG; n = 18), and normal tension glaucoma (NTG; n = 18) eyes. We used SS-OCT to obtain 3 x 3 mm cube scans of an area centered on the optic disc, and then synchronized reconstructed ...

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    20. Analysis of Retinal Nonperfusion Using Depth-Integrated Optical Coherence Tomography Images in Eyes with Branch Retinal Vein Occlusion

      Analysis of Retinal Nonperfusion Using Depth-Integrated Optical Coherence Tomography Images in Eyes with Branch Retinal Vein Occlusion

      PURPOSE: To assess the morphology of areas of complete retinal nonperfusion in eyes with branch retinal vein occlusion (BRVO) by enface images of optical coherence tomography (OCT). METHODS: Forty-six eyes with BRVO which underwent swept-source OCT (SS-OCT) and fluorescein angiography were enrolled. Depth-integrated images of the neural retina delineated by automated segmentation algorithm were obtained using SS-OCT. The findings in a 6 x 6-mm area on enface SS-OCT scans at the area of retinal nonperfusion were evaluated. RESULTS: Retinal nonperfusion was detected in twenty-five eyes. Of these, twenty (80%) eyes had multiple concaves of low reflectivity within an area of ...

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      Mentions: Osaka University
    21. Speckle reduction in optical coherence tomography by matrix completion using bilateral random projection

      Speckle reduction in optical coherence tomography by matrix completion using bilateral random projection

      Speckle noise is problematic in optical coherence tomography (OCT) and often obscures the structure details. In this paper, we propose a new method to reduce speckle noise from multiply scanned OCT slices. The proposed method registers the OCT scans using a global alignment followed by a local alignment based on global and local motion estimation. Then low rank matrix completion using bilateral random projection is utilized to estimate the noise and recover the clean image. Experimental results show that the proposed method archives average contrast to noise ratio 14.90, better than 13.78 by the state-of-the-art method used in ...

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    22. Ophthalmological Imaging Apparatus And Ophthalmological Image Display Device

      Ophthalmological Imaging Apparatus And Ophthalmological Image Display Device

      Provided is a novel technique for ophthalmological image diagnosis. The ophthalmological imaging apparatus according to an embodiment comprises: an acquisition unit for acquiring three dimensional image data for an eye being tested using optical coherence tomography; a designating section for designating partial image data, which is a portion of the three dimensional image data that corresponds to a specified region of the eye being tested; a modifying section for generating new three dimensional data by modifying the three dimensional data so that said partial image data is modified to a previously established form; a forming section for forming cross-sectional image ...

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    23. Speckle Reduction in Optical Coherence Tomography by Image Registration and Matrix Completion

      Speckle Reduction in Optical Coherence Tomography by Image Registration and Matrix Completion

      Speckle noise is problematic in optical coherence tomography (OCT). With the fast scan rate, swept source OCT scans the same position in the retina for multiple times rapidly and computes an average image from the multiple scans for speckle reduction. However, the eye movement poses some challenges. In this paper, we propose a new method for speckle reduction from multiply-scanned OCT slices. The proposed method applies a preliminary speckle reduction on the OCT slices and then registers them using a global alignment followed by a local alignment based on fast iterative diamond search. After that, low rank matrix completion using ...

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    24. En-face high-penetration optical coherence tomography imaging in polypoidal choroidal vasculopathy

      En-face high-penetration optical coherence tomography imaging in polypoidal choroidal vasculopathy

      Aim To observe the choroidal microstructure in polypoidal choroidal vasculopathy (PCV) using high-penetration optical coherence tomography (HP-OCT) with a long-wavelength light source that visualises tissue beneath the retinal pigment epithelium (RPE) and deep choroid, and to compare the findings with those of indocyanine green angiography (ICGA). Methods In this retrospective, non-invasive, observational case series, 19 eyes (18 patients) with PCV were observed using HP-OCT (swept source, 100 000 A-scans/s, 1060 nm wavelength) and ICGA. The HP-OCT scan protocol was a 3×3-mm or 6×6-mm square containing 256×256 or 512×128 A-scans. The choroidal thickness (CT) was measured ...

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