1. 1-24 of 405 1 2 3 4 ... 15 16 17 »
    1. Recovering distance information in spectral domain interferometry

      Recovering distance information in spectral domain interferometry

      This work evaluates the performance of the Complex Master Slave (CMS) method, that processes the spectra at the interferometer output of a spectral domain interferometry device without involving Fourier transforms (FT) after data acquisition. Reliability and performance of CMS are compared side by side with the conventional method based on FT, phase calibration with dispersion compensation (PCDC). We demonstrate that both methods provide similar results in terms of resolution and sensitivity drop-off. The mathematical operations required to produce CMS results are highly parallelizable, allowing real-time, simultaneous delivery of data from several points of different optical path differences in the interferometer ...

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    2. Usefulness of peripapillary nerve fiber layer thickness assessed by optical coherence tomography as a biomarker for Alzheimer’s disease

      Usefulness of peripapillary nerve fiber layer thickness assessed by optical coherence tomography as a biomarker for Alzheimer’s disease

      The use of optical coherence tomography (OCT) has been suggested as a potential biomarker for Alzheimer’s Disease based on previously reported thinning of the retinal nerve fiber layer (RNFL) in Alzheimer’s disease’s (AD) and Mild Cognitive Impairment (MCI). However, other studies have not shown such results. 930 individuals (414 cognitively healthy individuals, 192 probable amnestic MCI and 324 probable AD) attending a memory clinic were consecutively included and underwent spectral domain OCT (Maestro, Topcon) examinations to assess differences in peripapillary RNFL thickness, using a design of high ecological validity. Adjustment by age, education, sex and OCT image ...

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    3. Biophotonic approach for the characterization of initial bitter-rot progression on apple specimens using optical coherence tomography assessments

      Biophotonic approach for the characterization of initial bitter-rot progression on apple specimens using optical coherence tomography assessments

      The tremendous advances achieved in the biophotonics technologies have intensified the necessity for non-invasive modalities that can characterize diverse biological materials with increased sensitivity and resolution. Optical coherence tomography (OCT) is one of the techniques that has been applied for biological applications in medicine and agriculture to identify structural properties. Herein, we report the successful incorporation of OCT for the identification of morphological changes that occur as a result of the bitter rot disease, through continuous detection of structural changes. Detailed inner morphological structural changes occurring in fruit specimens were precisely analyzed as a function of the disease incubation period ...

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    4. Ability of swept source OCT to detect retinal changes in patients with bipolar disorder

      Ability of swept source OCT to detect retinal changes in patients with bipolar disorder

      Purpose To evaluate the ability of swept source optical coherence tomography (SS-OCT) to detect retinal changes in patients with bipolar disorder (BD). Methods Twenty-three patients with BD and 23 controls underwent retinal evaluation using SS deep range imaging (DRI) Triton OCT. Full retinal thickness, the ganglion cell layer (GCL), the retinal nerve fiber layer (RNFL), and choroidal thickness were evaluated with automated segmentation software. Results Patients with BD were shown to have significant thinning of the macular full retinal thickness in the center ( p  = 0.049), inner temporal ( p  = 0.045), inner nasal ( p  = 0.016), and inner inferior ( p ...

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    5. The diagnostic accuracy of OCT angiography in naive and treated neovascular age-related macular degeneration: a review

      The diagnostic accuracy of OCT angiography in naive and treated neovascular age-related macular degeneration: a review

      Optical coherence tomography angiography (OCTA) is a non-invasive retinal imaging innovation that has been gaining popularity for the evaluation of the retinal vasculature. Of clinical importance is its current use either as an alternative or in conjunction with conventional dye-based angiography in neovascular age-related macular degeneration. OCTA is not without limitations and these include image artefact, a relatively small field of view and failure of the segmentation algorithms, which can confound the interpretation of findings. While there are numerous publications on OCTA in neovascular AMD, few have examined the diagnostic accuracy of this new technology compared with the accepted gold ...

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    6. Visualizing large choroidal blood flow by subtraction of the choriocapillaris projection artifacts in swept source optical coherence tomography angiography in normal eyes

      Visualizing large choroidal blood flow by subtraction of the choriocapillaris projection artifacts in swept source optical coherence tomography angiography in normal eyes

      Optical coherence tomography angiography (OCTA) seems not to image the choroidal blood flow pattern in the normal individual because of the OCT light attenuation. Our purpose in the current study was to visualize the large choroidal blood flow pattern after subtraction of the choriocapillaris projection artifact in normal eyes non-invasively by swept source (SS) OCTA. Sixty-one eyes of 45 individuals (19 men, 26 women) without ocular disease were examined by SS-OCTA (AngioPlex Elite 9000, Zeiss, Germany). A 12 × 12 mm macular area was scanned. Subfoveal choroidal thickness (SCT) was measured, and the choroidal blood flow pattern in a slab of ...

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    7. Foveal avascular zone area measurements with optical coherence tomography angiography in patients with nanophthalmos

      Foveal avascular zone area measurements with optical coherence tomography angiography in patients with nanophthalmos

      Purpose To compare the area of the superficial foveal avascular zone (SFAZ) and deep foveal avascular zone (DFAZ) between patients with nanophthalmos and age matched controls. Methods This prospective and comparative study included 19 eyes from 11 patients with nanophthalmos (study group) and 19 eyes from 19 healthy subjects (control group). SFAZ and DFAZ were measured with optical coherence tomography angiography (OCT-A). All participants underwent a standardised ocular examination including best corrected visual acuity (BCVA), central macular thickness (CMT), subfoveal choroidal thickness (SFCT) anterior chamber depth (ACD), axial length (AL), and refractive error (RE) measurements. Results Mean SFAZ and DFAZ ...

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    8. Changes in volume of various retinal layers over time in early and intermediate age-related macular degeneration

      Changes in volume of various retinal layers over time in early and intermediate age-related macular degeneration

      Purpose To evaluate longitudinally volume changes in inner and outer retinal layers in early and intermediate age-related macular degeneration (AMD) compared to healthy control eyes using optical coherence tomography (OCT). Methods 71 eyes with AMD and 31 control eyes were imaged at two time points: baseline and after 2 years. Automated OCT layer segmentation was performed using Orion TM . This software is able to measure volumes of retinal layers with distinct boundaries including Retinal Nerve Fibre Layer (RNFL), Ganglion Cell-Inner Plexiform Layer (GCIPL), Inner Nuclear Layer (INL), Outer Plexiform Layer (OPL), Outer Nuclear Layer (ONL), Photoreceptors (PR) and Retinal Pigment ...

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    9. Biomedical Engineering & Ophthalmological Imaging

      Biomedical Engineering & Ophthalmological Imaging

      The Departments of Biomedical Engineering and Ophthalmology at The Johns Hopkins University seek exceptional applicants for a tenure-track faculty position in Biomedical Engineering & Ophthalmological Imaging. Outstanding candidates will be considered at all academic ranks and across all areas of functional and structural Biomedical Imaging. Candidates with expertise in developing and advancing state-of-the-art imaging technologies and medical devices for ocular research and clinical applications―e.g., multiphoton fluorescence or Raman microscopy, second and higher harmonics generation microscopy, super resolution microscopy, optical coherence tomography, adaptive optics, and laser-assisted surgical technologies―will be particularly competitive. Applicants specializing in the development of sensors, robotics ...

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    10. Two-photon polymerisation 3D printed freeform micro-optics for optical coherence tomography fibre probes

      Two-photon polymerisation 3D printed freeform micro-optics for optical coherence tomography fibre probes

      Miniaturised optical coherence tomography (OCT) fibre-optic probes have enabled high-resolution cross-sectional imaging deep within the body. However, existing OCT fibre-optic probe fabrication methods cannot generate miniaturised freeform optics, which limits our ability to fabricate probes with both complex optical function and dimensions comparable to the optical fibre diameter. Recently, major advances in two-photon direct laser writing have enabled 3D printing of arbitrary three-dimensional micro/nanostructures with a surface roughness acceptable for optical applications. Here, we demonstrate the feasibility of 3D printing of OCT probes. We evaluate the capability of this method based on a series of characterisation experiments. We report ...

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    11. En Face and Cross-sectional Corneal Tomograms Using Sub-micron spatial resolution Optical Coherence Tomography

      En Face and Cross-sectional Corneal Tomograms Using Sub-micron spatial resolution Optical Coherence Tomography

      Accurate diagnosis of corneal pathology and morphological identification of different corneal layers require clear delineation of corneal three-dimensional structures and en face or cross-sectional imaging of palisade of Vogt (POV), neovascularization (NV) or corneal nerves. Here we report a prototype of full-field optical coherence tomography (FF-OCT) system with isotropic sub-micron spatial resolution in the en face and cross-sectional views. It can also provide three-dimensional reconstructed images and a large field of view (FOV) by stitching tomograms side by side. We validated the imaging power of this prototype in in vivo rat and rabbit eyes, and quantified anatomical characteristics such as ...

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    12. Comprehensive intravascular imaging of atherosclerotic plaque in vivo using optical coherence tomography and fluorescence lifetime imaging

      Comprehensive intravascular imaging of atherosclerotic plaque in vivo using optical coherence tomography and fluorescence lifetime imaging

      Comprehensive imaging of both the structural and biochemical characteristics of atherosclerotic plaque is essential for the diagnosis and study of coronary artery disease because both a plaque’s morphology and its biochemical composition affect the level of risk it poses. Optical coherence tomography (OCT) and fluorescence lifetime imaging (FLIm) are promising optical imaging methods for characterizing coronary artery plaques morphologically and biochemically, respectively. In this study, we present a hybrid intravascular imaging device, including a custom-built OCT/FLIm system, a hybrid optical rotary joint, and an imaging catheter, to visualize the structure and biochemical composition of the plaque in an ...

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    13. Optical coherence tomography angiography features of choroidal neovascularization secondary to angioid streaks

      Optical coherence tomography angiography features of choroidal neovascularization secondary to angioid streaks

      Purpose To characterize the features of choroidal neovascularization (CNV) secondary to angioid streaks (AS) with optical coherence tomography angiography (OCT-A) and to assess its sensitivity in CNV detection in this particular context. Methods Consecutive patients, both with treatment-naïve and recurrent CNV associated with angioid streaks were prospectively analyzed. All patients underwent macular imaging by fluorescein angiography (FA), indocyanine green angiography (ICGA), spectral-domain (SD)-OCT, and OCT-A (AngioVue, Optovue, Optovue Inc., Freemont, CA, USA). OCT-A detection rate of CNV associated to AS was evaluated by two independent observers. We studied the association between OCT-A feature and either exudative or active ...

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    14. Predictive accuracy of partial coherence interferometry and swept-source optical coherence tomography for intraocular lens power calculation

      Predictive accuracy of partial coherence interferometry and swept-source optical coherence tomography for intraocular lens power calculation

      The purpose of this study is to compare the predictive accuracy of intraocular lens (IOL) calculations made with partial coherence interferometry (PCI, IOLMaster, version 5) and swept-source optical coherence tomography (SS-OCT, Argos). Axial length (AL), mean keratometry value (K), and anterior chamber depth (ACD) were obtained using PCI and SS-OCT optical biometers. Intraocular lens (IOL) power calculations were made using the Barret-Universal II, Haigis, Hoffer Q, SRK/T, and T2 formulas and compared the predictive accuracy between biometers. In 153 eyes (153 patients), axial length measurements made with PCI (24.65 ± 2.35 mm) and SS-OCT (24.62 ± 2.29 ...

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    15. The world at their feet

      The world at their feet

      As a summer intern at the private foundation Brain and Spine Institute (ICM) in Paris, Olivier Thouvenin helped develop an imaging technique for monitoring the neural circuitry in zebrafish larvae. But the method lacked the spatial resolution to tease apart connections between neurons at the single-cell level, which frustrated the young biophysics master’s student. So for his PhD at the Langevin Institute — two kilometres away on the edge of Paris’s famed Botanical Gardens — Thouvenin worked on improving an existing high-resolution tissue-imaging tool called full-field optical coherence tomography (OCT). He added a dynamic time element to the otherwise static ...

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    16. Quantitative progression of retinitis pigmentosa by optical coherence tomography angiography

      Quantitative progression of retinitis pigmentosa by optical coherence tomography angiography

      Optical coherence tomography angiography (OCT-A) is a non-invasive alternative to fluorescein angiography that allows for the study of the retinal and choroidal vasculatures. In this retrospective cohort study of 28 patients with retinitis pigmentosa (RP), we used OCT-A to quantify changes in perfusion density, foveal avascular zone (FAZ) area, and choriocapillaris blood flow over time and correlated these variables with ellipsoid zone (EZ) line width and best-corrected visual acuity (BCVA). Perfusion density decreased by 2.42 ± 0.62% per year at the superior capillary plexus (SCP) (P = 0.001) and 2.41 ± 0.76% per year at the deep capillary ...

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    17. Correlation of Color Fundus Photograph Grading with Risks of Early Age-related Macular Degeneration by using Automated OCT-derived Drusen Measurements

      Correlation of Color Fundus Photograph Grading with Risks of Early Age-related Macular Degeneration by using Automated OCT-derived Drusen Measurements

      We evaluated automated OCT-derived drusen volume measures in a population-based study (n = 4,512) aged ≥40 years, and its correlation with conventional color fundus photographs (CFP)-derived early AMD features. Participants had protocol-based assessment to capture medical and ocular history, genotyping for SNPs in CFH , ARMS2 , and CETP , CFP-based AMD grading and automated drusen volume based on SD-OCT using built-in software (Cirrus OCT advanced RPE analysis software). Significantly fewer eyes with early AMD features (drusen, hyperpigmentation, soft or reticular drusen) had drusen volume = 0 mm 3 (p < 0.001). In eyes with drusen volume > 0 mm 3 , increasing AMD severity ...

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    18. The Importance of Signal Strength in Quantitative Assessment of Retinal Vessel Density Using Optical Coherence Tomography Angiography

      The Importance of Signal Strength in Quantitative Assessment of Retinal Vessel Density Using Optical Coherence Tomography Angiography

      The quality of the scan image is important in microvascular circulation analysis using optical coherence tomography (OCTA). We aimed to investigate the effect of signal strength (SS) on OCTA metrics and minimum SS level that could be considered optimal. Macular 6 × 6 mm angiography images were acquired, and all subjects were divided into four groups according to the SS (SS 7, SS 8, SS 9, and SS 10) of the OCTA image. Vessel density (VD), perfusion density (PD), and foveal avascular zone (FAZ) metrics of the superficial capillary plexus were compared. In total, 446 eyes from young healthy subjects were ...

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    19. Integrating optical coherence tomography with gravimetric and video analysis (OCT-Gravimetry-Video method) for studying the drying process of polystyrene latex system

      Integrating optical coherence tomography with gravimetric and video analysis (OCT-Gravimetry-Video method) for studying the drying process of polystyrene latex system

      Latex, an aqueous dispersion of sub-micron polymer particles, is widely used as polymer binder in waterborne coatings and adhesives. Drying of a latex is inhomogeneous, during which the spatial distribution of particles is non-uniform and changes with time, usually resulting in a compromise of the integrity of a dried film. To study drying inhomogeneity of latex, we developed a system integrating optical coherence tomography (OCT) with gravimetric and video analysis (OCT-Gravimetry-Video method) to non-destructively monitor the drying process of non-film-forming latexes consisting of hard polystyrene spheres over time. OCT structural and speckle images of the latex’s internal structure show ...

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    20. Using spectral-domain optical coherence tomography to evaluate the type and thickness of interdigitation zone band in adult Chinese

      Using spectral-domain optical coherence tomography to evaluate the type and thickness of interdigitation zone band in adult Chinese

      To study types and thickness of interdigitation zone band in adult Chinese subjects, we conducted a cross-sectional study. The population-based Beijing Eye Study 2011 included 3468 individuals with a mean age of 64.6 ± 9.8 years. 263 people (263eyes) with a mean age of 64.8 years were randomly selected cases without macular diseases included in the study. A detailed ophthalmic examination was performed including SD-OCT for measurement of the thickness of interdigitation zone band. There are two types of interdigitation zone band; the type1 which can distinguish RPE–BM complex in 170 eyes; and the Type 2 which ...

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    21. Clinically applicable deep learning for diagnosis and referral in retinal disease

      Clinically applicable deep learning for diagnosis and referral in retinal disease

      The volume and complexity of diagnostic imaging is increasing at a pace faster than the availability of human expertise to interpret it. Artificial intelligence has shown great promise in classifying two-dimensional photographs of some common diseases and typically relies on databases of millions of annotated images. Until now, the challenge of reaching the performance of expert clinicians in a real-world clinical pathway with three-dimensional diagnostic scans has remained unsolved. Here, we apply a novel deep learning architecture to a clinically heterogeneous set of three-dimensional optical coherence tomography scans from patients referred to a major eye hospital. We demonstrate performance in ...

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    22. Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model

      Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model

      Corneal neovascularization (CoNV) could be treated by novel anti-angiogenic therapies, though reliable and objective imaging tools to evaluate corneal vasculature and treatment efficacy is still lacking. Optical coherence tomography angiography (OCTA) –currently designed as a retinal vascular imaging system— has been recently adapted for anterior-segment and showed good potential for successful imaging of CoNV. However, further development requires an animal model where parameters can be studied more carefully with histological comparison. Our study evaluated the OCTA in suture-induced CoNV in a rabbit model compared to indocyanine green angiography (ICGA) and slit-lamp photography (SLP). Overall vessel density measurements from OCTA showed ...

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    23. Novel application of In Vivo Micro-Optical Coherence Tomography to assess Cornea scarring in an Animal Model

      Novel application of In Vivo Micro-Optical Coherence Tomography to assess Cornea scarring in an Animal Model

      This pilot study uses a micro-optical coherence tomography (micro-OCT) system with ~1 μm axial resolution specifically to image the cornea and corneal scars in vivo . We used an established murine corneal scar model by irregular phototherapeutic keratectomy in ten C57BL/6 mice, with serial imaging using the micro-OCT and compared to anterior segment (AS-OCT) (RTvue, Optovue, Fremont, CA) before and after scar induction. Main outcome was agreement between the AS-OCT and micro-OCT using Bland-Altman plots (95% limits of agreement, LoA).We analysed 10 control eyes and 10 eyes with corneal scars and found that there was good agreement between AS-OCT ...

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    24. Deep brain optical coherence tomography angiography in mice: in vivo, noninvasive imaging of hippocampal formation

      Deep brain optical coherence tomography angiography in mice: in vivo, noninvasive imaging of hippocampal formation

      The hippocampus is associated with memory and navigation, and the rodent hippocampus provides a useful model system for studying neurophysiology such as neural plasticity. Vascular changes at this site are closely related to brain diseases, such as Alzheimer’s disease, dementia, and epilepsy. Vascular imaging around the hippocampus in mice may help to further elucidate the mechanisms underlying these diseases. Optical coherence tomography angiography (OCTA) is an emerging technology that can provide label-free blood flow information. As the hippocampus is a deep structure in the mouse brain, direct in vivo visualisation of the vascular network using OCTA and other microscopic ...

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