1. 1-24 of 482 1 2 3 4 ... 18 19 20 »
    1. Spatial analysis of thickness changes in ten retinal layers of Alzheimer’s disease patients based on optical coherence tomography

      Spatial analysis of thickness changes in ten retinal layers of Alzheimer’s disease patients based on optical coherence tomography

      The retina is an attractive source of biomarkers since it shares many features with the brain. Thickness differences in 10 retinal layers between 19 patients with mild Alzheimer’s disease (AD) and a control group of 24 volunteers were investigated. Retinal layers were automatically segmented and their thickness at each scanned point was measured, corrected for tilt and spatially normalized. When the mean thickness of entire layers was compared between patients and controls, only the outer segment layer of patients showed statistically significant thinning. However, when the layers were compared point-by point, patients showed statistically significant thinning in irregular regions ...

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    2. Two-dimensional simulation of optical coherence tomography images

      Two-dimensional simulation of optical coherence tomography images

      An algorithm for the simulation of two-dimensional spectral domain optical coherence tomography images based on Maxwell’s equations is presented. A recently developed and modified time-harmonic numerical solution of Maxwell’s equations is used to obtain scattered far fields for many wave numbers contained in the calculated spectrum. The interferometer setup with its lenses is included rigorously with Fresnel integrals and the Debye-Wolf integral. The implemented model is validated with an existing FDTD algorithm by comparing simulated tomograms of single and multiple cylindrical scatterers for perpendicular and parallel polarisation of the incident light. Tomograms are presented for different realisations of ...

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    3. Optical coherence refraction tomography

      Optical coherence refraction tomography

      Optical coherence tomography (OCT) is a cross-sectional, micrometre-scale imaging modality with widespread clinical application. Typical OCT systems sacrifice lateral resolution to achieve long depths of focus for bulk tissue imaging, and therefore tend to have better axial than lateral resolution. Such anisotropic resolution can obscure fine ultrastructural features. Furthermore, conventional OCT suffers from refraction-induced image distortions. Here, we introduce optical coherence refraction tomography (OCRT), which extends the superior axial resolution to the lateral dimension, synthesizing undistorted cross-sectional image reconstructions from multiple conventional images acquired with angular diversity. In correcting refraction-induced distortions to register the OCT images, OCRT also achieves spatially ...

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    4. Correlations between visual acuity and macular microvasculature quantified with optical coherence tomography angiography in diabetic macular oedema

      Correlations between visual acuity and macular microvasculature quantified with optical coherence tomography angiography in diabetic macular oedema

      Purpose To explore the impact of macular ischaemia on vision in diabetic macular oedema (DMO) by analysing the correlations between visual acuity and macular microvascular parameters using optical coherence tomography angiography (OCTA). Methods OCTA was performed in 81 eyes of 48 patients with DMO, and 3 × 3-mm 2 en face OCTA images of the superficial capillary plexus and deep capillary plexus in the central macula were retrospectively collected. Microvascular parameters including the number of microaneurysms, area of foveal avascular zone (FAZ), acircularity index of FAZ, vessel density, skeleton density, vessel density index and fractal dimension were measured. Central retinal thickness ...

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    5. Correlation between pigmented arc and epithelial thickness (COPE) study in orthokeratology-treated patients using OCT measurements

      Correlation between pigmented arc and epithelial thickness (COPE) study in orthokeratology-treated patients using OCT measurements

      Purpose To determine the intensity of corneal pigmented arc in orthokeratology (ortho-k)-treated children, and its correlation with key epithelial thickness measurements obtained by anterior segment optical coherence tomography (AS-OCT). Methods This study is a retrospective case series. Medical records of children who received ortho-k treatment for myopia control in our hospital were reviewed. Intensity of ortho-k-associated pigmented arc and its correlation with key epithelial thickness parameters in the central 7-mm-diameter zone obtained by AS-OCT was examined. The subjects were further divided into apparent and unapparent pigmented arc groups for severity comparison. Results The mean age of children was 11 ...

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    6. Assessment of Choroidal Thickness Inside and Outside of Vascular Arcade in Diabetic Retinopathy Eyes Using Spectral-Domain Optical Coherence Tomography

      Assessment of Choroidal Thickness Inside and Outside of Vascular Arcade in Diabetic Retinopathy Eyes Using Spectral-Domain Optical Coherence Tomography

      This study aimed to characterise the distribution of choroidal thickness (CT) in diabetic retinopathy eyes, inside and outside of the vascular arcade, as well as at the fovea, using spectral-domain optical coherence tomography (OCT). Forty-nine healthy eyes, 80 diabetic retinopathy (DR) eyes (59 non-proliferative diabetic retinopathy (NPDR) eyes and 21 proliferative diabetic retinopathy (PDR) eyes) were examined with OCT to obtain nine horizontal lines (far superotemporal, near superotemporal, central, near inferotemporal, far inferotemporal, far superonasal, near superonasal, near inferonasal, far inferonasal) inside and outside of the vascular arcade. Nine points were chosen in 0.5-mm intervals to calculate CT, which ...

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    7. High-resolution multimodal photoacoustic microscopy and optical coherence tomography image-guided laser induced branch retinal vein occlusion in living rabbits

      High-resolution multimodal photoacoustic microscopy and optical coherence tomography image-guided laser induced branch retinal vein occlusion in living rabbits

      Joint high-resolution multimodal photoacoustic microscopy (PAM) and optical coherence tomography (OCT) was developed to improve the efficiency for visualizing newly developed retinal neovascularization (RNV) and to monitor the dynamic changes of retinal vein occlusion (RVO) in living rabbits. The RNV and RVO models were created in New Zealand rabbits by Rose Bengal laser-induced RVO. Dual modalities imaging equipment, including color fundus photography, fluorescein angiography (FA), OCT, and PAM, was used to image and assess the changes of retinal vasculature. In vivo experimental results exhibited that not only the treatment boundaries and the position of the occluded vasculature but also the ...

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    8. Optical coherence tomography complements confocal microscopy for investigation of multicellular tumour spheroids

      Optical coherence tomography complements confocal microscopy for investigation of multicellular tumour spheroids

      Knowledge of optical properties, such as the refractive index (RI), of biological tissues is important in optical imaging, as they influence the distribution and propagation of light in tissue. To accurately study the response of cancerous cells to drugs, optimised imaging protocols are required. This study uses a simple custom-built spectral domain optical coherence tomography (OCT) system to conduct RI measurements of multicellular spheroids, three-dimensional (3D) in-vitro culture systems, of the cell line HCT116. The spheroid RIs are compared to study the effect of growth over time. To improve confocal microscopy imaging protocols, two immersion media (glycerol and ScaleView-A2) matching ...

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    9. Observation of treated iris neovascularization by swept-source-based en-face anterior-segment optical coherence tomography angiography

      Observation of treated iris neovascularization by swept-source-based en-face anterior-segment optical coherence tomography angiography

      We evaluated regression of iris neovascularization (INV) using en-face anterior-segment optical coherence tomography angiography (AS-OCTA) after anti-vascular endothelial growth factor (VEGF) therapy. Seven consecutive eyes with INV were examined before and after anti-VEGF therapy, and all AS-OCTA scans were obtained using a swept-source OCTA system with an anterior-segment lens adapter. Slit-lamp microscopy photography and anterior indocyanine green angiography also were performed. Quantitative analyses of the vascular density, vascular lacunarity, and fractal dimension on AS-OCTA images were performed. AS-OCTA visualized the INV as signals around the pupillary margin, which corresponded to the vasculature confirmed by slit-lamp microscopy. After anti-VEGF drug injection ...

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      Mentions: Osaka University
    10. Immediate effects of smoking on optic nerve and macular perfusion measured by optical coherence tomography angiography

      Immediate effects of smoking on optic nerve and macular perfusion measured by optical coherence tomography angiography

      The aim of this study was the assessment of the relationship between cigarette smoking and optic nerve and macular vessel density measured by optical coherence tomography angiography. We examined 30 eyes from 30 healthy habitual smokers. The examination was performed using a high-speed and high-resolution spectral-domain optical coherence tomography RTVue XR Avanti with AngioVue (Optovue, Fremont, CA, USA) with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, vascular density in the area of the optic nerve head (4.5*4.5 mm) and vascular density with the foveal avascular zone in the central macula (3.0*3.0 mm ...

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      Mentions: Optovue
    11. Optical coherence tomography angiography findings in preeclampsia

      Optical coherence tomography angiography findings in preeclampsia

      Objectives To investigate vascular density analysis in the superficial (SCP) and deep capillary plexus (DCP), foveal avascular zone (FAZ), peripapillary vascular density analysis (PPCVD), and peripapillary retinal nerve fiber thickness analysis (PPRNFL) using optical coherence tomography angiography (OCTA) in pregnant women with preeclampsia and to compare the obtained values with healthy pregnant and nonpregnant healthy individuals. Methods A total of 98 pregnant women (55 had preeclampsia, 43 were healthy pregnant women) and 38 healthy nonpregnant women of reproductive age were included in the study. The patients were divided into three groups. Group 1 consisted of pregnant women with preeclampsia, group ...

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    12. Swept-Source Optical Coherence Tomography Biometer as Screening Strategy for Macular Disease in Patients Scheduled for Cataract Surgery

      Swept-Source Optical Coherence Tomography Biometer as Screening Strategy for Macular Disease in Patients Scheduled for Cataract Surgery

      The aim of this study was to assess the central macular imaging captured with an optical biometer based on full-eye-length Swept-Source OCT (SS-OCT) scan as a screening strategy for identifying macular diseases in patients scheduled for cataract surgery. 1,114 eyes of 749 consecutive patients underwent a biometrical examination with IOLMaster 700 SS-OCT technology (Carl Zeiss) and conventional Spectral-Domain OCT (SD-OCT) (Spectralis OCT, Heidelberg) device analysis on the same day. Seven examiners graded the scans individually in a full-masked mode. Twenty-five eyes were excluded for media opacities. Among the 1,089 included eyes, statistical analysis revealed a mean Kendall’s ...

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    13. Detecting Retinal Nerve Fibre Layer Segmentation Errors on Spectral Domain-Optical Coherence Tomography with a Deep Learning Algorithm

      Detecting Retinal Nerve Fibre Layer Segmentation Errors on Spectral Domain-Optical Coherence Tomography with a Deep Learning Algorithm

      n this study we developed a deep learning (DL) algorithm that detects errors in retinal never fibre layer (RNFL) segmentation on spectral-domain optical coherence tomography (SDOCT) B-scans using human grades as the reference standard. A dataset of 25,250 SDOCT B-scans reviewed for segmentation errors by human graders was randomly divided into validation plus training (50%) and test (50%) sets. The performance of the DL algorithm was evaluated in the test sample by outputting a probability of having a segmentation error for each B-scan. The ability of the algorithm to detect segmentation errors was evaluated with the area under the ...

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    14. Bacterial Density and Biofilm Structure Determined by Optical Coherence Tomography

      Bacterial Density and Biofilm Structure Determined by Optical Coherence Tomography

      Optical-coherence-tomography (OCT) is a non-destructive tool for biofilm imaging, not requiring staining, and used to measure biofilm thickness and putative comparison of biofilm structure based on signal intensity distributions in OCT-images. Quantitative comparison of biofilm signal intensities in OCT-images, is difficult due to the auto-scaling applied in OCT-instruments to ensure optimal quality of individual images. Here, we developed a method to eliminate the influence of auto-scaling in order to allow quantitative comparison of biofilm densities in different images. Auto- and re-scaled signal intensities could be qualitatively interpreted in line with biofilm characteristics for single and multi-species biofilms of different strains ...

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    15. Effect of cold provocation on vessel density in eyes with primary open angle glaucoma: An optical coherence tomography angiography study

      Effect of cold provocation on vessel density in eyes with primary open angle glaucoma: An optical coherence tomography angiography study

      The cold pressor test (CPT) induces a cardiovascular response, which may affect ocular blood flow and neuronal function. This study assessed whether optical coherence tomography angiography (OCT-A) can be used to evaluate CPT-induced changes in healthy eyes and in eyes with primary open-angle glaucoma (POAG). Twenty-two healthy subjects and 23 subjects with POAG and retinal fibre layer defects in only one hemifield were included in this study. The CPT was performed by submerging a subject’s hand in cold water (0–4 °C) for 1 minute. The results showed that baseline peripapillary and macular vessel density (VD) measurements were significantly ...

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    16. Foveal abnormalities determined by optical coherence tomography angiography in children with history of retinopathy of prematurity

      Foveal abnormalities determined by optical coherence tomography angiography in children with history of retinopathy of prematurity

      Purpose To describe the foveal characteristics of children with a history of retinopathy of prematurity (ROP) using optical coherence tomography angiography (OCTA). Methods All eyes were examined by OCTA (RTVue AVANTI, Optovue Inc, Fremont, CA) with a scan of 3 × 3 mm cantered on the fovea. The size of the foveal avascular zone (FAZ), central retinal thickness (CRT), and foveal bulge were measured. Results Forty-eight eyes of 26 children with a history of ROP and a mean age of 8.8 years with a range of 4–16 years (ROP group) were studied. Sixty-six eyes of 36 children without any ...

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    17. Optical coherence tomography angiography study of the retinal vascular plexuses in type 1 diabetes without retinopathy

      Optical coherence tomography angiography study of the retinal vascular plexuses in type 1 diabetes without retinopathy

      Aim Previous data suggest the existence of retinal vascular changes and impaired autoregulation in the very early stages of diabetic retinopathy (DR). We compared the retinal plexuses between patients with type 1 diabetes (T1D) without DR and a demographically similar healthy cohort, using optical coherence tomography angiography (OCT-A). Methods Patients with T1D and no signs of DR were prospectively recruited from an outpatient clinic. Using OCT-A (AngioVue ® ), the parafoveal superficial (SCP) and deep (DPC) capillary plexus as well as the foveal avascular zone (FAZ) and perimeter were gathered. Mean comparison tests and linear regression analysis were used as statistical tests ...

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    18. Early response to the treatment of choroidal neovascularization complicating central serous chorioretinopathy: a OCT-angiography study

      Early response to the treatment of choroidal neovascularization complicating central serous chorioretinopathy: a OCT-angiography study

      Purpose To analyze the quantitative and qualitative early changes of choroidal neovascularization (CNV) associated with chronic central serous chorioretinopathy (CSC) after treatment using optical coherence tomography-angiography (OCT-A). Methods Charts of consecutive patients with diagnosis of chronic CSC complicated by CNV were retrospectively reviewed. Included patients were divided in photodynamic therapy (PDT) or aflibercept group on the basis of the treatment received (half-fluence PDT or aflibercept 2.0 mg/0.05 ml intravitreal injection). Main outcome measures included the changes between baseline and 1-month follow-up in CNV vessel density (VD) and area on OCT-A images after thresholding and binarization. Results A ...

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    19. Controlling for Artifacts in Widefield Optical Coherence Tomography Angiography Measurements of Non-Perfusion Area

      Controlling for Artifacts in Widefield Optical Coherence Tomography Angiography Measurements of Non-Perfusion Area

      The recent clinical adoption of optical coherence tomography (OCT) angiography (OCTA) has enabled non-invasive, volumetric visualization of ocular vasculature at micron-scale resolutions. Initially limited to 3 mm × 3 mm and 6 mm × 6 mm fields-of-view (FOV), commercial OCTA systems now offer 12 mm × 12 mm, or larger, imaging fields. While larger FOVs promise a more complete visualization of retinal disease, they also introduce new challenges to the accurate and reliable interpretation of OCTA data. In particular, because of vignetting, wide-field imaging increases occurrence of low-OCT-signal artifacts, which leads to thresholding and/or segmentation artifacts, complicating OCTA analysis. This study presents ...

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    20. Quantitative analysis of the macula with optical coherence tomography angiography in normal Japanese subjects: The Taiwa Study

      Quantitative analysis of the macula with optical coherence tomography angiography in normal Japanese subjects: The Taiwa Study

      This study evaluated age-related changes in the superficial and deep retinal capillary plexus (SCP and DCP, respectively) and in the foveal avascular zone (FAZ). SCP and DCP perfusion density (PD) were measured in optical coherence tomography angiography (OCTA) macular scans of 145 eyes of 145 healthy Japanese subjects, and findings were compared with SCP FAZ and clinical data. We found that age was negatively correlated with SCP and DCP PD (r = −0.17, P  = 0.04 and r = −0.20, P  = 0.02, respectively) and positively correlated with FAZ area (r = 0.18, P  = 0.03). SCP and DCP PD ...

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    21. Flow Density in Optical Coherence Tomography Angiography is Useful for Retinopathy Diagnosis in Diabetic Patients

      Flow Density in Optical Coherence Tomography Angiography is Useful for Retinopathy Diagnosis in Diabetic Patients

      Our study evaluated the diagnostic capability of flow density (FD) in OCT angiography (OCTA) for diabetic retinopathy (DR) detection in diabetic patients. We studied 93 eyes of 68 diabetic patients who underwent OCTA (36 and 57 eyes without and with DR, respectively). Retinal capillary FD of a 2.6 × 2.6 mm 2 area and four divided areas at the superficial (SCP) and deep capillary plexus (DCP) were measured. Predictions were evaluated using the area under the receiver operating characteristic curve (AUC). The diagnostic capabilities of the FDs in discriminating between eyes without DR and eyes with total or early ...

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    22. Optical Coherence Tomography Angiography for Diagnosis of Choroidal Neovascularization in Chronic Central Serous Chorioretinopathy after Photodynamic Therapy

      Optical Coherence Tomography Angiography for Diagnosis of Choroidal Neovascularization in Chronic Central Serous Chorioretinopathy after Photodynamic Therapy

      The authors evaluated the proportion of choroidal neovascularization (CNV) detected by spectral-domain optical coherence tomography angiography (OCTA) in eyes with chronic central serous chorioretinopathy (CSC) (more than 3 months) with previous treatment via half-dose photodynamic therapy (PDT). All patients were followed up with at least twelve months. Macular angiograms were obtained using spectral-domain OCT (SD-OCT, RTVue XR; Optovue). CNV was defined as flow in the outer retinal slab between the outer plexiform layer and Bruch’s membrane. Clinical characteristics were compared between CNV and non-CNV groups. Seventy eyes of 61 patients (51 male and 10 female) were included. The average ...

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      Mentions: Optovue
    23. Interference effects in quantum-optical coherence tomography using spectrally engineered photon pairs

      Interference effects in quantum-optical coherence tomography using spectrally engineered photon pairs

      Optical-coherence tomography (OCT) is a technique that employs light in order to measure the internal structure of semitransparent, e.g. biological, samples. It is based on the interference pattern of low-coherence light. Quantum-OCT (QOCT), instead, employs the correlation properties of entangled photon pairs, for example, generated by the process of spontaneous parametric downconversion (SPDC). The usual QOCT scheme uses photon pairs characterised by a joint-spectral amplitude with strict spectral anti-correlations. It has been shown that, in contrast with its classical counterpart, QOCT provides resolution enhancement and dispersion cancellation. In this paper, we revisit the theory of QOCT and extend the ...

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    24. Morphologic and functional outcomes of different optical coherence tomography patterns of myopic foveoschisis after vitrectomy and inner limiting membrane peeling

      Morphologic and functional outcomes of different optical coherence tomography patterns of myopic foveoschisis after vitrectomy and inner limiting membrane peeling

      Objective To evaluate the morphologic and functional outcomes of different optical coherence tomography (OCT) patterns of myopic foveoschisis after vitrectomy with Inner Limiting Membrane (ILM) peeling. Methods In this prospective non-randomised study, 62 consecutive eyes with Myopic Foveoschisis were categorised into three groups according to OCT pattern: retinoschisis type (Rt) Group (23/62), foveal detachment type (FDt) Group (20/62) and macular hole type (MHt) Group (19/62). All patients underwent 25-Gauge vitrectomy and ILM peeling. Air or gas tamponade was used. All patients were observed at month 1, 2, 4 and 6 after surgery. Main outcomes measures: surgical success ...

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