1. Articles from Kazuhiro Kurokawa

    1-18 of 18
    1. Method to investigate temporal dynamics of ganglion and other retinal cells in the living human eye

      Method to investigate temporal dynamics of ganglion and other retinal cells in the living human eye

      The inner retina is critical for visual processing, but much remains unknown about its neural circuitry and vulnerability to disease. A major bottleneck has been our inability to observe the structure and function of the cells composing these retinal layers in the living human eye. Here, we present a noninvasive method to observe both structural and functional information. Adaptive optics optical coherence tomography (AO-OCT) is used to resolve the inner retinal cells in all three dimensions and novel post processing algorithms are applied to extract structure and physiology down to the cellular level. AO-OCT captured the 3D mosaic of individual ...

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    2. Imaging and quantifying ganglion cells and other transparent neurons in the living human retina [Engineering]

      Imaging and quantifying ganglion cells and other transparent neurons in the living human retina [Engineering]

      Ganglion cells (GCs) are fundamental to retinal neural circuitry, processing photoreceptor signals for transmission to the brain via their axons. However, much remains unknown about their role in vision and their vulnerability to disease leading to blindness. A major bottleneck has been our inability to observe GCs and their degeneration in the living human eye. Despite two decades of development of optical technologies to image cells in the living human retina, GCs remain elusive due to their high optical translucency. Failure of conventional imaging—using predominately singly scattered light—to reveal GCs has led to a focus on multiply-scattered, fluorescence ...

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    3. Tracking dynamics of photoreceptor disc shedding with adaptive optics-optical coherence tomography

      Tracking dynamics of photoreceptor disc shedding with adaptive optics-optical coherence tomography

      Absorption of light by photoreceptors initiates vision, but also leads to accumulation of toxic photo-oxidative compounds in the photoreceptor outer segment (OS). To prevent this buildup, small packets of OS discs are periodically pruned from the distal end of the OS, a process called disc shedding. Unfortunately dysfunction in any part of the shedding event can lead to photoreceptor and RPE dystrophy, and has been implicated in numerous retinal diseases, including age related macular degeneration and retinitis pigmentosa. While much is known about the complex molecular and signaling pathways that underpin shedding, all of these advancements have occurred in animal ...

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    4. Adaptive optics optical coherence tomography angiography for morphometric analysis of choriocapillaris [Invited]

      Adaptive optics optical coherence tomography angiography for morphometric analysis of choriocapillaris [Invited]

      Histological studies have shown that morphometric changes at the microscopic level of choriocapillaris (CC) occur with aging and disease onset, and therefore may be sensitive biomarkers of outer retinal health. However, visualizing CC at this level in the living human eye is challenging because its microvascular is tightly interconnected and weakly reflecting. In this study, we address these challenges by developing and validating a method based on adaptive optics optical coherence tomography with angiography (AO-OCTA) that provides the necessary 3D resolution and image contrast to visualize and quantify these microscopic details. The complex network of anastomotic CC capillaries was successfully ...

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    5. Photoreceptor disc shedding in the living human eye

      Photoreceptor disc shedding in the living human eye

      Cone photoreceptors undergo a daily cycle of renewal and shedding of membranous discs in their outer segments (OS), the portion responsible for light capture. These physiological processes are fundamental to maintaining photoreceptor health, and their dysfunction is associated with numerous retinal diseases. While both processes have been extensively studied in animal models and postmortem eyes, little is known about them in the living eye, in particular human. In this study, we report discovery of the optical signature associated with disc shedding using a method based on adaptive optics optical coherence tomography (AO-OCT) in conjunction with post-processing methods to track and ...

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    6. Investigation of Thermal Effects of Photocoagulation on Retinal Tissue Using Fine-Motion-Sensitive Dynamic Optical Coherence Tomography

      Investigation of Thermal Effects of Photocoagulation on Retinal Tissue Using Fine-Motion-Sensitive Dynamic Optical Coherence Tomography

      To enable an objective evaluation of photocoagulation, we characterize thermal tissue changes induced by laser irradiation with different laser parameters using optical coherence tomography (OCT). Spectral-domain OCT with a newly developed image processing method was used to monitor the thermal changes of ex vivo porcine retina. A sequence of OCT B-scans was obtained at the same retinal position simultaneously with the photocoagulation. Cross-sectional tissue displacement maps with respect to an OCT image taken before laser irradiation were computed for images taken before, during, and after laser irradiation, by using a correlation-based custom algorithm. Cross-sectional correlation maps (OCT correlation maps) were ...

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    7. Quantitative optical coherence tomography by maximum a-posteriori estimation of signal intensity

      Quantitative optical coherence tomography by maximum a-posteriori estimation of signal intensity

      A maximum a-posteriori (MAP) estimator for signal amplitude of optical coherence tomography (OCT) is presented. This estimator provides an accurate and low bias estimation of the correct OCT signal amplitude even at very low signal-tonoise ratios. As a result, contrast improvement of retinal OCT images is demonstrated. In addition, this estimation method allows for an estimation reliability to be calculated. By combining the MAP estimator with a previously demonstrated attenuation imaging algorithm, we present attenuation coefficient images of the retina. From the reliability derived from the MAP image one can also determine which regions of the attenuation images are unreliable ...

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    8. Noise-immune complex correlation for vasculature imaging based on standard and Jones-matrix optical coherence tomography

      Noise-immune complex correlation for vasculature imaging based on standard and Jones-matrix optical coherence tomography

      A new optical coherence angiography (OCA) method, called correlation mapping OCA (cmOCA), is presented by using the SNR-corrected complex correlation. An SNR-correction theory for the complex correlation calculation is presented. The method also integrates a motion-artifact-removal method for the sample motion induced decorrelation artifact. The theory is further extended to compute more reliable correlation by using multi- channel OCT systems, such as Jones-matrix OCT. The high contrast vasculature imaging of in vivo human posterior eye has been obtained. Composite imaging of cmOCA and degree of polarization uniformity indicates abnormalities of vasculature and pigmented tissues simultaneously.

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    9. Maximum a posteriori estimator for high-contrast image composition of optical coherence tomography

      Maximum a posteriori estimator for high-contrast image composition of optical coherence tomography

      A quantitative signal amplitude estimator for optical coherence tomography (OCT) is presented. It is based on a statistical model of OCT signal and noise, using a Bayesian maximum a posteriori (MAP) estimation framework. Multiple OCT images are used for estimation, similar to the widely utilized intensity averaging method. The estimator is less biased especially at low-intensity regions, where intensity averaging approaches the noise power and hence is biased. The estimator is applied to posterior ocular OCT images and provides high-contrast visualization of pathologies. In addition, histogram analysis objectively shows the superior performance of the estimator compared with intensity averaging.

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    10. In-plane and out-of-plane tissue micro-displacement measurement by correlation coefficients of optical coherence tomography

      In-plane and out-of-plane tissue micro-displacement measurement by correlation coefficients of optical coherence tomography

      We propose a method to measure the in-plane and out-of-plane displacements of tissue using the correlation coefficients of optical coherence tomography (OCT) signals. The displacements are determined by the local correlation coefficients between digitally shifted reference OCT images and a target image. The method achieves sub-micron displacement measurement with an accuracy better than 0.32 μm and repeatability better than 0.36 μm. The feasibility of the method was examined by measuring the displacement field of a laser irradiated porcine retina. This method successfully visualized the dynamic change of the displacement field during laser irradiation.

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    11. Two-dimensional micro-displacement measurement for laser coagulation using optical coherence tomography

      Two-dimensional micro-displacement measurement for laser coagulation using optical coherence tomography

      To improve the reproducibility of photocoagulation, the ability to quantitatively monitor the thermal change of laser-irradiated retinal tissue is required. Recently, optical coherence tomography has enabled non-invasive and non-contact monitoring of the tissue structural changes during laser irradiation. To further improve the capability of this technique, a method is proposed to measure tissue displacement by simultaneously using Doppler phase shifts and correlation coefficients. The theoretical approach for this method is described, and its performance is experimentally confirmed and evaluated. Finally, lateral and axial displacements in the laser-irradiated retinal tissues of an enucleated porcine eye are observed. The proposed method is ...

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    12. Quantitative two-dimensional micro-displacement measurement by optical coherence tomography

      Quantitative two-dimensional micro-displacement measurement by optical coherence tomography

      There are several applications of quantitative micro-displacement measurement of a biological specimen, including characterization of mechanical property and monitoring a laser-induced photothermal expansion. In this study, we proposed a quantitative micro-displacement measurement method using optical coherence tomography (OCT). Specifically, the axial displacement is measured by Doppler OCT and magnitude of displacement is measured by correlation coefficient. By using this method, we measured the local and microdisplacement of the chicken muscles during laser irradiation. The proposed method successfully visualizes thermal changes of chicken muscle due to the laser irradiation. The measured displacement and deformation are useful information for the further understanding ...

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    13. Advanced multi-contrast Jones matrix optical coherence tomography for Doppler and polarization sensitive imaging

      Advanced multi-contrast Jones matrix optical coherence tomography for Doppler and polarization sensitive imaging

      An advanced version of Jones matrix optical coherence tomography (JMT) is demonstrated for Doppler and polarization sensitive imaging of the posterior eye. JMT is capable of providing localized flow tomography by Doppler detection and investigating the birefringence property of tissue through a three-dimensional (3-D) Jones matrix measurement. Owing to an incident polarization multiplexing scheme based on passive optical components, this system is stable, safe in a clinical environment, and cost effective. Since the properties of this version of JMT provide intrinsic compensation for system imperfection, the system is easy to calibrate. Compared with the previous version of JMT, this advanced ...

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    14. Three-dimensional retinal and choroidal capillary imaging by power Doppler optical coherence angiography with adaptive optics

      Three-dimensional retinal and choroidal capillary imaging by power Doppler optical coherence angiography with adaptive optics

      Retinal and choroidal vascular imaging is a key to the better understanding and diagnosis of eye diseases. To achieve comprehensive three-dimensional capillary imaging, we used an enhanced vascular imaging technique, so called adaptive optics optical coherence angiography (AO-OCA). AO-OCA enables in vivo high-resolution and high-contrast micro-vascular imaging by detecting Doppler frequency shifts. Using this technique, the retinal and choroidal vasculatures of healthy subjects were imaged. The results show that both intensity and Doppler power images have sufficient contrast to discriminate almost all vasculatures from the static tissue. However, the choriocapillaris, pre-arterioles, and post-venules in the Sattler layer were more contrasted ...

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    15. Extended depth of focus adaptive optics spectral domain optical coherence tomography

      Extended depth of focus adaptive optics spectral domain optical coherence tomography
      We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the ...
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    16. Simultaneous high-resolution retinal imaging and high-penetration choroidal imaging by one-micrometer adaptive optics optical coherence tomography

      Simultaneous high-resolution retinal imaging and high-penetration choroidal imaging by one-micrometer adaptive optics optical coherence tomography
      Adaptive optics optical coherence tomography (AO-OCT) provides three-dimensional high-isotropic-resolution retinal images in vivo. We developed AO-OCT with a 1.03-μm probing beam and demonstrated high-penetration, high-resolution retinal imaging. Axial scans are acquired with a speed of 47,000 lines/s. AO closed loop is configured with a single deformable mirror. Seven eyes of 7 normal subjects were examined. Signal enhancement was found for all subjects. A rippled interface between nerve fiber layer and ganglion cell layer, boundary between ganglion cell layer and inner plexiform layer, and chorioscleral interface were identified. Simultaneous high-resolution and high-penetration choroidal imaging may be useful for ...
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    17. Adaptive optics spectral domain optical coherence tomography with one-micrometer light source

      Adaptive optics spectral domain optical coherence tomography with one-micrometer light source
      Adaptive optics spectral domain optical coherence tomography (AO SD-OCT) has provided three-dimensional high isotropic resolution retinal images in vivo. In order to enhance the image quality of deep region of the eye, the alternative wavelength of 1-µm has been used for ophthalmic OCT. This study aims to develop AO SD-OCT with one-micrometer probe and demonstrated high penetration and high resolution retinal imaging. A broadband 1-µm SLD light source (Suplerlum) have the center wavelength of 1.03 µm and the spectral bandwidth of 106 nm. Axial scans were obtained by an InGaAs line scan camera with the speed of 47,000 ...
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    18. Adaptive optics retinal scanner for one-micrometer light source

      Adaptive optics retinal scanner for one-micrometer light source
      We developed an adaptive optics (AO) retinal scanner by using a light source with a center wavelength of 1-um. In a recent study on optical coherence tomography (OCT), it was proved that 1-um light provided higher image contrast of deep region of the eye than 840-nm light. Further, high lateral resolution retinal images were obtained with AO. In this study, we performed measurements on two normal subjects in the AO-SLO mode and analyzed its performance toward developing the AO-OCT. With AO correction, we found that the residual RMS wavefront error of ocular aberration was less than 0.1 μm. We ...
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    1-18 of 18
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  2. Topics in the News

    1. (13 articles) University of Tsukuba
    2. (13 articles) Shuichi Makita
    3. (12 articles) Yoshiaki Yasuno
    4. (6 articles) National Institutes of Health
    5. (5 articles) Zhuolin Liu
    6. (5 articles) Donald T. Miller
    7. (4 articles) Indiana University
    8. (4 articles) Masahiro Miura
    9. (3 articles) Center for Ophthalmic Optics and Lasers
    10. (3 articles) Oregon Health & Science University
    11. (3 articles) David Huang
    12. (2 articles) Harvard University
    13. (2 articles) Massachusetts General Hospital
    14. (2 articles) University of Southern California
    15. (2 articles) Brett E. Bouma
    16. (2 articles) Johannes F. de Boer
    17. (2 articles) Mohamed Abou Shousha
    18. (1 articles) Purdue University
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    Adaptive optics retinal scanner for one-micrometer light source Adaptive optics spectral domain optical coherence tomography with one-micrometer light source Simultaneous high-resolution retinal imaging and high-penetration choroidal imaging by one-micrometer adaptive optics optical coherence tomography Extended depth of focus adaptive optics spectral domain optical coherence tomography Three-dimensional retinal and choroidal capillary imaging by power Doppler optical coherence angiography with adaptive optics Advanced multi-contrast Jones matrix optical coherence tomography for Doppler and polarization sensitive imaging Quantitative two-dimensional micro-displacement measurement by optical coherence tomography In-plane and out-of-plane tissue micro-displacement measurement by correlation coefficients of optical coherence tomography Photoreceptor disc shedding in the living human eye Tracking dynamics of photoreceptor disc shedding with adaptive optics-optical coherence tomography The impact of blood pressure variability on coronary arterial lumen dimensions as assessed by optical coherence tomography in patients with ST-elevation myocardial infarction Clinical diversity in macular corneal dystrophy: an optical coherence tomography study