Other affiliations: Utsunomiya University
Bio: Yiheng Lim is an academic researcher from University of Tsukuba. The author has contributed to research in topics: Optical coherence tomography & Birefringence. The author has an hindex of 12, co-authored 21 publications receiving 593 citations. Previous affiliations of Yiheng Lim include Utsunomiya University.
TL;DR: An advanced version of Jones matrix optical coherence tomography (JMT) is demonstrated for Doppler and polarization sensitive imaging of the posterior eye and a new theory of JMT which integrates the Jones matrix measurement, doppler measurement, and scattering measurement is presented, which enables a sensitivity-enhanced scattering OCT and high-sensitivity Dopplers OCT.
Abstract: 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 JMT achieves a sufficiently long depth measurement range for clinical cases of posterior eye disease. Furthermore, a fine spectral shift compensation method based on the cross-correlation of calibration signals was devised for stabilizing the phase of OCT, which enables a high sensitivity Doppler OCT measurement. In addition, a new theory of JMT which integrates the Jones matrix measurement, Doppler measurement, and scattering measurement is presented. This theory enables a sensitivity-enhanced scattering OCT and high-sensitivity Doppler OCT. These new features enable the application of this system to clinical cases. A healthy subject and a geographic atrophy patient were measured in vivo, and simultaneous imaging of choroidal vasculature and birefringence structures are demonstrated.
TL;DR: This system measures Doppler flow without extra hardware for phase stabilized SS-OCT detection and measurement of optic nerve head of a retina and detailed vasculature and birefringent structures were investigated simultaneously.
Abstract: 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.
TL;DR: This study develops polarization-sensitive swept-source OCT at 1 microm for deep penetration of the sclera and lamina cribrosa in the posterior part of human eyes and shows polarization-insensitive intensity images, in which an artifact created by the birefringence of sClera has been successfully eliminated.
Abstract: 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-SS-OCT) at 1 microm 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, 11.0 microm, 94.2 dB, respectively. The posterior part of the eyes of a healthy male subject are measured in vivo. Phase-retardation images show birefringence of deep sclera and lamina cribrosa and enhance the contrast which is not visible in the intensity images. In addition, unlike conventional OCT, our PS-SS-OCT showed polarization-insensitive intensity images, in which an artifact created by the birefringence of sclera has been successfully eliminated.
TL;DR: Retinal imaging was demonstrated using the PS-SS-OCT system with a frequency-swept laser at a center wavelength of 1064 nm and an axial resolution of 11.4 microm in tissue, which showed characteristic birefringence of fibrous tissues such as retinal nerve fiber, sclera, and lamina cribrosa.
Abstract: 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 directions, these methods can be combined to make the optimum use of both full range and polarization-sensitive imaging. Phase fluctuations that cause measurement failure were numerically canceled before demodulating the B-scan oriented modulation. After removing complex conjugate artifacts, the axial measurement range was 5.35 mm, and the signal-to-conjugate ratio was 40.5 dB. We demonstrated retinal imaging using the PS-SS-OCT system with a frequency-swept laser at a center wavelength of 1064 nm and an axial resolution of 11.4 µm in tissue. Full-range polarization-sensitive retinal images showed characteristic birefringence of fibrous tissues such as retinal nerve fiber, sclera, and lamina cribrosa.
TL;DR: PS-OCT showed promising for the study and diagnosis diseases related to abnormal fibrous tissues of the cornea and anterior eye segment related to glaucoma patients treated by trabeculectomy and keratoconus cases with advanced thinning and with a rupture of Descemet's membrane.
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.
TL;DR: In this article, optical coherence tomography is used for high-resolution, noninvasive imaging of the human retina, including the macula and optic nerve head in normal human subjects.
Abstract: Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.
TL;DR: The profile of choroidal thickness depends on its location, and RE, axial length, and especially age are critical for evaluation of chiroidal thickness.
Abstract: Purpose. To study posterior choroidal thickness and its profile based on location in healthy Japanese subjects and the correlation with axial length, refractive error (RE), and age. Methods. Eighty-six eyes of 43 healthy volunteers with no ophthalmic or systemic symptoms were examined with prototype high-penetration optical coherence tomography using a 1060-nm light source. Eyes with high myopia (exceeding -6 D) or with retinal/choroidal disease were excluded. The spherical equivalent RE was measured by autorefractometry, and the axial length was measured by partial coherence inferometry. Results. Mean choroidal thicknesses were 354 +/- 111 mum at the fovea, 364 +/- 86 mum superiorly, 345 +/- 108 mum inferiorly, 227 +/- 532 mum nasally, and 337 +/- 102 mum temporally. Subfoveal choroidal thickness was significantly greater than nasal (P < 0.01) and temporal (P < 0.05) choroidal thickness; however, there was no significant difference compared with superior (P = 0.20) and inferior (P = 0.17) choroidal thickness. The temporal choroid was significantly (P < 0.01) thicker than the nasal choroid, and the inferior choroid was significantly (P < 0.01) thinner than the superior choroid. There was a significant negative correlation between foveal choroidal thickness and axial length (P < 0.05) but a borderline correlation with the RE (P = 0.086) and age (P = 0.07). Age was the factor that was most associated with the choroidal thickness (F = 20.86; P < 0.001), followed by RE (F = 5.37; P < 0.05); axial length was not a significant factor (F = 1.47; P = 0.22) by stepwise analysis. Conclusions. The profile of choroidal thickness depends on its location. RE, axial length, and especially age are critical for evaluation of choroidal thickness.
TL;DR: In this article, a polarization-sensitive optical coherence-domain reflectometer capable of characterizing the phase retardation between orthogonal linear polarization modes at each reflection point in a birefringent sample is presented.
Abstract: We present a polarization-sensitive optical coherence-domain reflectometer capable of characterizing the phase retardation between orthogonal linear polarization modes at each reflection point in a birefringent sample. The device is insensitive to the rotation of the sample in the plane perpendicular to ranging. Phase measurement accuracy is ±0.86°, but the reflectometer can distinguish local variations in birefringence as small as 0.05° with a distance resolution of 10.8 μm and a dynamic range of 90 dB. Birefringence-sensitive ranging in a wave plate, an electro-optic modulator, and a calf coronary artery is demonstrated.
TL;DR: Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin.
Abstract: Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.
TL;DR: The fundamental limitations and advantages of time-domain and Fourier-domain interferometric detection methods are discussed, and new perspectives on functional imaging with the use of state-of-the-art high-speed OCT technology are demonstrated.
Abstract: In the past decade we have observed a rapid development of ultrahigh-speed optical coherence tomography (OCT) instruments, which currently enable performing cross-sectional in vivo imaging of biological samples with speeds of more than 100,000 A-scans/s. This progress in OCT technology has been achieved by the development of Fourier-domain detection techniques. Introduction of high-speed imaging capabilities lifts the primary limitation of early OCT technology by giving access to in vivo three-dimensional volumetric reconstructions on large scales within reasonable time constraints. As result, novel tools can be created that add new perspective for existing OCT applications and open new fields of research in biomedical imaging. Especially promising is the capability of performing functional imaging, which shows a potential to enable the differentiation of tissue pathologies via metabolic properties or functional responses. In this contribution the fundamental limitations and advantages of time-domain and Fourier-domain interferometric detection methods are discussed. Additionally the progress of high-speed OCT instruments and their impact on imaging applications is reviewed. Finally new perspectives on functional imaging with the use of state-of-the-art high-speed OCT technology are demonstrated.