1. Articles from Yiheng Lim

    1-16 of 16
    1. Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

      Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

      An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680–940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip ...

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    2. Developmental and morphological studies in Japanese medaka with ultra-high resolution optical coherence tomography

      Developmental and morphological studies in Japanese medaka with ultra-high resolution optical coherence tomography

      We propose ultra-high resolution optical coherence tomography to study the morphological development of internal organs in medaka fish in the post-embryonic stages at micrometer resolution. Different stages of Japanese medaka were imaged after hatching in vivo with an axial resolution of 2.8 µm in tissue. Various morphological structures and organs identified in the OCT images were then compared with the histology. Due to the medaka’s close resemblance to vertebrates, including humans, these morphological features play an important role in morphogenesis and can be used to study diseases that also occur in humans.

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      Mentions: Barry Cense
    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. In vivo evaluation of human skin anisotropy by polarization-sensitive optical coherence tomography

      In vivo evaluation of human skin anisotropy by polarization-sensitive optical coherence tomography
      We performed an in vivo three-dimensional analysis of anisotropic changes in the dermal birefringence of mechanically deformed human skin using polarization-sensitive optical coherence tomography (PS-OCT). The papillary-dermal birefringence of the forehead increased significantly when the skin was shrunk parallel to the body axis, and decreased significantly when the skin was shrunk perpendicular to the body axis. En-face images of the papillary-dermal birefringence revealed variations among individual subjects, and that both shrinking parallel to and stretching in perpendicular to the body axis promoted the formation of macro rope-like birefringent domains. We found that PS-OCT is useful for understanding anisotropic properties of ...
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    11. Monte-Carlo-based phase retardation estimator for polarization sensitive optical coherence tomography

      Monte-Carlo-based phase retardation estimator for polarization sensitive optical coherence tomography
      A Monte-Carlo-based phase retardation estimator is developed to correct the systematic error in phase retardation measurement by polarization sensitive optical coherence tomography (PS-OCT). Recent research has revealed that the phase retardation measured by PS-OCT has a distribution that is neither symmetric nor centered at the true value. Hence, a standard mean estimator gives us erroneous estimations of phase retardation, and it degrades the performance of PS-OCT for quantitative assessment. In this paper, the noise property in phase retardation is investigated in detail by Monte-Carlo simulation and experiments. A distribution transform function is designed to eliminate the systematic error by using ...
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    12. Birefringence measurement of cornea and anterior segment by office-based polarization-sensitive optical coherence tomography

      Birefringence measurement of cornea and anterior segment by office-based polarization-sensitive optical coherence tomography
      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 ...
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    13. Multimodal analysis of pearls and pearl treatments by using optical coherence tomography and fluorescence spectroscopy

      Multimodal analysis of pearls and pearl treatments by using optical coherence tomography and fluorescence spectroscopy
      , , , , , , , We present an integrated optical system that consists of optical coherence tomography (OCT) and laser-induced fluorescence (LIF) spectroscopy for multimodal analysis of pearls and pearl treatments. The OCT source and the LIF excitation beams were aligned together to illuminate the same spot of a ... [Opt. Express 19, 6420-6432 (2011)]
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    14. Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation

      Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation
      Polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) is used to measure three-dimensional phase-retardation images of birefringent biological tissue in vivo. PS-SS-OCT with continuous source polarization modulation is used to multiplex the incident states of polarization in the signal frequency of each A-scan. Although it offers the advantage of measurement speed that is as high as that of standard SS-OCT, its disadvantage is low axial measurement range. To overcome this drawback, we employed the B-M-mode scan (BM-scan) method, which removes complex conjugate ambiguity by applying phase modulation along the transversal scanning direction. Since polarization modulation and BM-scan are applied in different scanning ...
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    15. Polarization sensitive corneal and anterior segment swept-source optical coherence tomography

      Polarization sensitive corneal and anterior segment swept-source optical coherence tomography
      We develop a compact polarization sensitive corneal and anterior segment swept-source optical coherence tomography (PS-CAS- OCT) for evaluating the usefulness of PS-OCT, and enabling large scale studies in the tissue properties of normal and diseased eyes using the benefits of the PS-OCT, which provides better tissue discrimination compared to the conventional OCT by visualizing the fibrous tissues in the anterior eye segment. Our polarization-sensitive interferometer is size reduced into a 19 inch box for the portability and the probe is integrated into a position adjustable scanning head for the usability of our system.
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    16. Visualization of phase retardation of deep posterior eye by polarization-sensitive swept-source optical coherence tomography with1-µm probe

      Visualization of phase retardation of deep posterior eye by polarization-sensitive swept-source optical coherence tomography with1-µm probe
      Polarization-sensitive optical coherence tomography (PS-OCT) can measure cross-sectional and volumetric images of birefringence in fibrous tissues that provides additional contrast to the intensity images. In this study, we develop polarization-sensitive swept-source OCT (PS-SSOCT) at 1 μm for deep penetration of the sclera and lamina cribrosa in the posterior part of human eyes. A calibration method for polarization mode dispersion of a circulator, which is employed to conserve the optical power of the interferometer and achieve system sensitivity sufficient for retinal imaging is demonstrated. The A-scan rate, the axial resolution, and the sensitivity of the PS-SS-OCT are 28,000 Hz, 11 ...
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    1-16 of 16
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    1. (14 articles) University of Tsukuba
    2. (14 articles) Yoshiaki Yasuno
    3. (12 articles) Masahiro Yamanari
    4. (6 articles) Shuichi Makita
    5. (4 articles) Masahiro Miura
    6. (2 articles) Tokyo Medical University
    7. (2 articles) Myeong Jin Ju
    8. (2 articles) Tomey Corporation
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    Visualization of phase retardation of deep posterior eye by polarization-sensitive swept-source optical coherence tomography with1-µm probe Polarization sensitive corneal and anterior segment swept-source optical coherence tomography Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation Multimodal analysis of pearls and pearl treatments by using optical coherence tomography and fluorescence spectroscopy Birefringence measurement of cornea and anterior segment by office-based polarization-sensitive optical coherence tomography Monte-Carlo-based phase retardation estimator for polarization sensitive optical coherence tomography In vivo evaluation of human skin anisotropy by polarization-sensitive optical coherence tomography Office based multi-functional anterior eye segment optical coherence tomography Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging Optical Rheology of Porcine Sclera by Birefringence Imaging Optical Technology Stepping Forward ― Utility of Intracoronary Optical Coherence Tomography ― Comment on ‘Swept‐source optical coherence tomography angiography reveals vascular changes in intermediate uveitis