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    1. Soliton microcomb based spectral domain optical coherence tomography

      Soliton microcomb based spectral domain optical coherence tomography

      Spectral domain optical coherence tomography (OCT) is a widely employed, minimally invasive bio-medical imaging technique, which requires a broadband light source, typically implemented by super-luminescent diodes. Recent advances in soliton based photonic integrated frequency combs (soliton microcombs) have enabled the development of low-noise, broadband chipscale frequency comb sources, whose potential for OCT imaging has not yet been unexplored. Here, we explore the use of dissipative Kerr soliton microcombs in spectral domain OCT and show that, by using photonic chipscale Si 3 N 4 resonators in conjunction with 1300 nm pump lasers, spectral bandwidths exceeding those of commercial OCT sources are ...

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    2. A pilot study investigating anterior segment optical coherence tomography angiography as a non-invasive tool in evaluating corneal vascularisation

      A pilot study investigating anterior segment optical coherence tomography angiography as a non-invasive tool in evaluating corneal vascularisation

      The current assessment of corneal vascularisation (CV) relies on slit-lamp examination, which may be subjective. Dye-based angiographies, like indocyanine green angiography (ICGA), allows for good visualisation of anterior segment blood vessels. However, ICGA is invasive and can be associated with systemic adverse effects. Anterior segment optical coherence tomography angiography (AS-OCTA) is a non-invasive tool that has been shown to successfully delineate CV. However, there are no previous studies that have reported if AS-OCTA can determine CV stage and activity. We used an established CV model in rabbits to examine serial AS-OCTA scans of CV development and regression following treatment with ...

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    3. Foveal avascular zone segmentation in optical coherence tomography angiography images using a deep learning approach

      Foveal avascular zone segmentation in optical coherence tomography angiography images using a deep learning approach

      The purpose of this study was to introduce a new deep learning (DL) model for segmentation of the fovea avascular zone (FAZ) in en face optical coherence tomography angiography (OCTA) and compare the results with those of the device’s built-in software and manual measurements in healthy subjects and diabetic patients. In this retrospective study, FAZ borders were delineated in the inner retinal slab of 3 × 3 enface OCTA images of 131 eyes of 88 diabetic patients and 32 eyes of 18 healthy subjects. To train a deep convolutional neural network (CNN) model, 126 enface OCTA images (104 eyes with ...

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    4. Repeatability of automated measurements by a new anterior segment optical coherence tomographer and biometer and agreement with standard devices

      Repeatability of automated measurements by a new anterior segment optical coherence tomographer and biometer and agreement with standard devices

      We assess repeatability of automatic measurements of a new anterior segment optical coherence tomographer and biometer (ANTERION) and their agreement with those provided by an anterior segment-optical coherence tomography device combined with Placido-disk corneal topography (MS-39) and a validated optical biometer (IOLMaster 500). A consecutive series of patients underwent three measurements with ANTERION and one with MS-39. A subgroup of patients underwent biometry also with IOLMaster 500. Repeatability was assessed by means of within-subject standard deviation, coefficient of variation (COV), and intraclass correlation coefficient (ICC). Agreement was investigated with the 95% limits of agreement. Paired t-test and Wilcoxon matched-pairs test ...

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    5. A preliminary study of post-progressive nail-art effects on in vivo nail plate using optical coherence tomography-based intensity profiling assessment

      A preliminary study of post-progressive nail-art effects on in vivo nail plate using optical coherence tomography-based intensity profiling assessment

      Nail beautification is a widely applied gender independent practice. Excessive nail beautifications and nail-arts have a direct impact on the nail structure and can cause nail disorders. Therefore, the assessment of post-progressive nail-art effects on the nail is essential to maintain optimal nail health and to avoid any undesirable disorders. In this study, in vivo nails were examined in control stage, with a nail-art stage, and after removing the nail-art stage using a 1310 nm spectral-domain optical coherence tomography (SD-OCT) system. The acquired cross-sectional OCT images were analyzed by a laboratory customized signal processing algorithm to obtain scattered intensity profiling ...

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    6. Effect of amblyopia treatment on macular microvasculature in children with anisometropic amblyopia using optical coherence tomographic angiography

      Effect of amblyopia treatment on macular microvasculature in children with anisometropic amblyopia using optical coherence tomographic angiography

      To measure the retinal microvascular density in patients with anisometropic amblyopia using optical coherence tomographic angiography (OCTA) and to evaluate the effects of successful amblyopia treatment on microvasculature in retina. 59 children (5–12 years old) including 22 newly diagnosed unilateral anisometropic amblyopia, 16 recovered unilateral anisometropic amblyopia, and 21 control children were imaged with OCTA using 6 × 6-mm macular scan pattern. Vessel densities of the superficial capillary plexus (SCP), the deep capillary plexus (DCP), and the overall macular thickness were acquired and compared among the three groups. After adjustment for axial length, the amblyopia group showed lower macular vessel ...

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    7. Structural and microvascular changes of the peripapillary retinal nerve fiber layer in Von Hippel–Lindau disease: an OCT and OCT angiography study

      Structural and microvascular changes of the peripapillary retinal nerve fiber layer in Von Hippel–Lindau disease: an OCT and OCT angiography study

      Von Hippel-Lindau (VHL) disease is an autosomal dominant genetic disease caused by VHL gene mutation. Retinal hemangioblastomas (RH) are vascularized tumors and represent the main ocular manifestation of the disease. Histopathologically, RH are composed of capillary vessels and stromal cells, the neoplastic population of the lesion. The origin of these stromal cells remains controversial, even if they are hypothesized to be glial cells. The aim of the present study was to investigate neuronal and microvascular changes of the peripapillary retinal nerve fiber layer, in which glial cells, neurons and capillaries (the radial peripapillary capillary plexus) interact. VHL patients with or ...

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    8. Global optical coherence tomography measures for detecting the progression of glaucoma have fundamental flaws

      Global optical coherence tomography measures for detecting the progression of glaucoma have fundamental flaws

      Objective To understand the problems involved in using global OCT measures for detecting progression in early glaucoma. Subjects/Methods Eyes from 76 patients and 28 healthy controls (HC) had a least two OCT scans at least 1 year apart. To determine the 95% confidence intervals (CI), 151 eyes (49 HC and 102 patients) had at least two scans within 6 months. All eyes had 24-2 mean deviation ≥-6dB. The average (global) thicknesses of the circumpapillary retinal nerve fibre layer (cRNFL), G ONH , and of the retinal ganglion cell layer plus inner plexiform layer (RGCLP), G mac , were calculated. Using quantile ...

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    9. Chain-like gold nanoparticle clusters for multimodal photoacoustic microscopy and optical coherence tomography enhanced molecular imaging

      Chain-like gold nanoparticle clusters for multimodal photoacoustic microscopy and optical coherence tomography enhanced molecular imaging

      Colloidal gold nanoparticles (GNPs) serve as promising contrast agents in photoacoustic (PA) imaging, yet their utility is limited due to their absorption peak in the visible window overlapping with that of hemoglobin. To overcome such limitation, this report describes an ultrapure chain-like gold nanoparticle (CGNP) clusters with a redshift peak wavelength at 650 nm. The synthesized CGNP show an excellent biocompatibility and photostability. These nanoparticles are conjugated with arginine-glycine-aspartic acid (RGD) peptides (CGNP clusters-RGD) and validated in 12 living rabbits to perform multimodal photoacoustic microscopy (PAM) and optical coherence tomography (OCT) for visualization of newly developed blood vessels in the ...

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    10. Toward optical coherence tomography on a chip: in vivo three-dimensional human retinal imaging using photonic integrated circuit-based arrayed waveguide gratings

      Toward optical coherence tomography on a chip: in vivo three-dimensional human retinal imaging using photonic integrated circuit-based arrayed waveguide gratings

      In this work, we present a significant step toward in vivo ophthalmic optical coherence tomography and angiography on a photonic integrated chip. The diffraction gratings used in spectral-domain optical coherence tomography can be replaced by photonic integrated circuits comprising an arrayed waveguide grating. Two arrayed waveguide grating designs with 256 channels were tested, which enabled the first chip-based optical coherence tomography and angiography in vivo three-dimensional human retinal measurements. Design 1 supports a bandwidth of 22 nm, with which a sensitivity of up to 91 dB (830 µW ) and an axial resolution of 10.7 µm was measured. Design 2 ...

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    11. Effect of vessel enhancement filters on the repeatability of measurements obtained from widefield swept-source optical coherence tomography angiography

      Effect of vessel enhancement filters on the repeatability of measurements obtained from widefield swept-source optical coherence tomography angiography

      We assessed the inter-visit repeatability of 15 × 9-mm 2 swept-source OCTA (SS-OCTA; PLEX Elite 9000, Carl Zeiss Meditec) metrics in 14 healthy participants. We analysed the perfusion density (PD) of large vessels, superficial capillary plexus (SCP), and deep capillary plexus (DCP) as well as choriocapillaris flow voids in 2 different regions: the macular region and peripheral region. Also, retinal plexus metrics were processed further using different filters (Hessian, Gabor and Bayesian) while choriocapillaris flow voids were calculated with 1 and 1.25 standard deviation (SD) thresholding algorithms. We found excellent repeatability in the perfusion densities of large vessels (ICC > 0 ...

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    12. Morphological changes in and quantitative analysis of macular retinal microvasculature by optical coherence tomography angiography in hypertensive retinopathy

      Morphological changes in and quantitative analysis of macular retinal microvasculature by optical coherence tomography angiography in hypertensive retinopathy

      Hypertension is a serious global health problem. Hypertensive retinopathy is generally considered to be a predictor of vascular disease elsewhere in the human body. In the past few decades, a variety of grading systems have been proposed for hypertensive retinopathy. However, these grading systems have some limitations. This study utilized optical coherence tomography angiography (OCTA) to investigate the morphological changes and macular retinal microvasculature in depth among 100 patients with hypertensive retinopathy and 66 healthy participants. Five main pathological changes were discovered in hypertensive retinopathy, as follows: focal capillary sparsity, scattered microangioma, focal macular arch ring defects, focal capillary disorder ...

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    13. OCTA evaluation of treatment-naïve flat irregular PED (FIPED)-associated CNV in chronic central serous chorioretinopathy before and after half-dose PDT

      OCTA evaluation of treatment-naïve flat irregular PED (FIPED)-associated CNV in chronic central serous chorioretinopathy before and after half-dose PDT

      Background To qualitatively and quantitatively evaluate the features of treatment-naïve flat irregular pigment epithelial detachment (FIPED)-associated choroidal neovascularization (CNV) in chronic central serous chorioretinopathy (CSC) using swept-source (SS) optical coherence tomography angiography (OCTA) before and after half-dose photodynamic therapy (PDT). Methods Retrospective case series. The multimodal imaging data of the eyes with FIPED-associated CNV in chronic CSC were reviewed. The features of FIPED-associated CNVs were evaluated by SS-OCTA. Results Records of twenty-one patients (21 eyes) were reviewed. The mean age was 56.62 ± 6.87 years. After half-dose PDT, all patients have improved best spectacle-corrected visual acuity from ...

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    14. Phenotyping of retinal neovascularization in ischemic retinal vein occlusion using wide field OCT angiography

      Phenotyping of retinal neovascularization in ischemic retinal vein occlusion using wide field OCT angiography

      Background/objectives Abnormal retinal neovascularization caused by ischemic retinal vein occlusion (RVO) is a frequent cause of visually significant vitreous hemorrhage. The early detection of new vessels may be challenging and often requires the use of invasive tests such as fundus fluorescein angiography (FA). We demonstrate the use of wide-field optical coherence tomography angiography (WF-OCTA) in the detection and characterization of neovascularization secondary to ischemic RVO. Subjects/methods We conducted a retrospective observational case series of patients diagnosed with ischemic RVO between August 2018 and March 2019, who underwent WF-SS-OCTA imaging (PLEX Elite 9000, Carl Zeiss Meditec). We performed real-life ...

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    15. Optical coherence tomography-based machine learning for predicting fractional flow reserve in intermediate coronary stenosis: a feasibility study

      Optical coherence tomography-based machine learning for predicting fractional flow reserve in intermediate coronary stenosis: a feasibility study

      Machine learning approaches using intravascular optical coherence tomography (OCT) to predict fractional flow reserve (FFR) have not been investigated. Both OCT and FFR data were obtained for left anterior descending artery lesions in 125 patients. Training and testing groups were partitioned in the ratio of 5:1. The OCT-based machine learning-FFR was derived for the testing group and compared with wire-based FFR in terms of ischemia diagnosis (FFR ≤ 0.8). The OCT-based machine learning-FFR showed good correlation (r = 0.853, P < 0.001) with the wire-based FFR. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the ...

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    16. Optical coherence tomography angiography for identifying choroidal neovascular membranes: a masked study in clinical practice

      Optical coherence tomography angiography for identifying choroidal neovascular membranes: a masked study in clinical practice

      Background/objectives Optical coherence tomography angiography (OCT-A) allows non-invasive imaging of chorio-retinal vasculature, and is a potential alternative to fluorescein angiography (FA). Sensitivity and specificity of OCT-A for detecting choroidal neovascularisation (CNV) in treatment-naïve neovascular age-related macular degeneration (nAMD) patients is examined, using the Heidelberg Spectralis in a ‘real world’ setting. Subject/methods Overall, 43 eyes from 26 patients were included in the study. Spectral domain OCT (SD-OCT), OCT-A and FA images were obtained at baseline. Each of the three retinal image modalities was systematically assessed by three masked clinicians. Decisions about the presence/absence of CNV were recorded ...

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    17. Preclinical ocular features in patients with Behçet’s disease detected by optical coherence tomography angiography

      Preclinical ocular features in patients with Behçet’s disease detected by optical coherence tomography angiography

      Objective The aim of this study was to evaluate the perifoveal and peripapillary microvascular structure in patients with Behçet’s disease (BD) without clinically ocular involvement. Methods Fifty-six eyes of 28 patients with Behçet’s disease without clinically ocular involvement and 50 age-matched healthy eyes were included in this prospective study. Vessel densities (VD) of macula and optic nerve head, foveal avascular zone (FAZ), choroid capillary plexus (CCP) flow area, perifoveal capillary nonperfusion, capillary dilatation and/or telangiectasia and perifoveal capillary arcade disruption were analyzed with optical coherence tomography angiography (OCTA). The relationship between duration of disease and ...

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    18. Optical coherence tomography (OCT) in neuro-ophthalmology

      Optical coherence tomography (OCT) in neuro-ophthalmology

      Optical coherence tomography (OCT) is a non-invasive medical imaging technology that is playing an increasing role in the routine assessment and management of patients with neuro-ophthalmic conditions. Its ability to characterise the optic nerve head, peripapillary retinal nerve fibre layer and cellular layers of the macula including the ganglion cell layer enables qualitative and quantitative assessment of optic nerve disease. In this review, we discuss technical features of OCT and OCT-based imaging techniques in the neuro-ophthalmic context, potential pitfalls to be aware of, and specific applications in more common neuro-ophthalmic conditions including demyelinating, inflammatory, ischaemic and compressive optic neuropathies, optic ...

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    19. Identification of plaque ruptures using a novel discriminative model comprising biomarkers in patients with acute coronary syndrome

      Identification of plaque ruptures using a novel discriminative model comprising biomarkers in patients with acute coronary syndrome

      Soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1), neutrophil gelatinase-associated lipocalin (NGAL), and matrix metalloproteinase-9 (MMP-9) are inflammatory biomarkers involved in plaque destabilization resulting in acute coronary syndrome (ACS). This study aimed to investigate the diagnostic value of a combination of biomarkers to discriminate plaque ruptures in the setting of ACS. Eighty-five ACS patients with optical coherence tomography (OCT) images of the culprit plaque were included and categorized into two groups: ACS with plaque rupture (Rupture group, n = 42) or without plaque rupture (Non-rupture group, n = 43) verified by OCT. A discriminative model of plaque rupture using several biomarkers was developed ...

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      Mentions: Korea University
    20. Intact in vivo visualization of telencephalic microvasculature in medaka using optical coherence tomography

      Intact in vivo visualization of telencephalic microvasculature in medaka using optical coherence tomography

      To date, various human disease models in small fish—such as medaka (Oryzias lapties)—have been developed for medical and pharmacological studies. Although genetic and environmental homogeneities exist, disease progressions can show large individual differences in animal models. In this study, we established an intact in vivo angiographic approach and explored vascular networks in the telencephalon of wild-type adult medaka using the spectral-domain optical coherence tomography. Our approach, which required neither surgical operations nor labeling agents, allowed to visualize blood vessels in medaka telencephala as small as about 8 µm, that is, almost the size of the blood cells of ...

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    21. The architecture of corneal stromal striae on optical coherence tomography and histology in an animal model and in humans

      The architecture of corneal stromal striae on optical coherence tomography and histology in an animal model and in humans

      The purpose of this study was to use a portable optical coherence tomography (OCT) for characterization of corneal stromal striae (CSS) in an ovine animal model and human corneas with histological correlation, in order to evaluate their architectural pattern by image analysis. Forty-six eyes from female adult sheep (older than 2 years), and 12 human corneas, were included in our study. The eyes were examined in situ by a portable OCT, without enucleation. All OCT scans were performed immediately after death, and then the eyes were delivered to a qualified histology laboratory. In the ovine animal model, CSS were detected ...

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    22. Validation of red blood cell flux and velocity estimations based on optical coherence tomography intensity fluctuations

      Validation of red blood cell flux and velocity estimations based on optical coherence tomography intensity fluctuations

      We present a validation of red blood cell flux and speed measurements based on the passage of erythrocytes through the OCT’s focal volume. We compare the performance of the so-called RBC-passage OCT technique to co-localized and simultaneously acquired two-photon excitation fluorescence microscopy (TPEF) measurements. Using concurrent multi-modal imaging, we show that fluctuations in the OCT signal display highly similar features to TPEF time traces. Furthermore, we demonstrate an overall difference in RBC flux and speed of 2.5 ± 3.27 RBC/s and 0.12 ± 0.67 mm/s (mean ± S.D.), compared to TPEF. The analysis also revealed ...

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    23. 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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    24. Ocular imaging at the cutting-edge

      Ocular imaging at the cutting-edge

      Barely three decades ago, ophthalmic images were mostly limited to film-based slit-lamp photography, fundus photography, fluorescein angiography (FA) and B-scan ultrasounds. With the rapid development in digital imaging technology and computer processing power, multiple innovative ocular imaging investigations have become available and are now essential parts of our daily clinical practice. In this special issue of Eye , experts from around the world summarised the recent major advancements in ocular imaging and their impacts in various fields of ophthalmology. One of the most remarkable development in the field of ocular imaging is the optical coherence tomography (OCT). OCT has greatly enhanced ...

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