1. 1-24 of 252 1 2 3 4 ... 9 10 11 »
    1. Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

      Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

      Recent developments in optical coherence tomography (OCT) systems for the cornea have limited resolution or acquisition speed. In this study we aim to evaluate the use of a ‘micro-OCT’ (μOCT ~1 μm axial resolution) compared to existing imaging modalities using animal models of corneal endothelial disease. We used established cryoinjury and bullous keratopathy models in Sprague Dawley rats comparing ex vivo μOCT imaging in normal and diseased eyes to (1) histology; (2) in vivo confocal microscopy (IVCM); and (3) scanning electron microscopy (SEM). Qualitative and quantitative comparisons amongst imaging modalities were performed using mean endothelial cell circularity [(4π × Area)/Perimeter ...

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    2. Spectral-domain optical coherence tomography findings of the macula in 500 consecutive patients with uveitis

      Spectral-domain optical coherence tomography findings of the macula in 500 consecutive patients with uveitis

      Purpose To analyze the macular structure in a large series of consecutive patients with different types of uveitis using spectral-domain optical coherence tomography (SD-OCT). Patients and methods Five hundred eyes of 500 consecutive patients with anterior, intermediate, posterior, and panuveitis underwent standardized macular examination using SD-OCT. Central retinal thickness (CRT), macular volume (MV), and presence of cystoid macular edema (CME), diffuse macular edema (DME), serous retinal detachment (SRD), epiretinal membrane with (ERM + ) and without (ERM−) retinal surface wrinkling were determined. Results The anatomic location of inflammation affected significantly CRT and MV (P<0.001, respectively), with the highest values in ...

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    3. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

      In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

      Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to ...

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    4. Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

      Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

      Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex ...

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    5. Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography

      Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography

      The decorrelation signals in optical coherence tomography angiography (OCTA) are derived from the flow of erythrocytes and concomitantly delineate the retinal vasculature. We compared the structural and functional characteristics of vascular lesions visualized in fluorescein angiography (FA), OCTA, and en-face OCT images in 53 eyes (28 patients) with diabetic retinopathy (DR). The foveal avascular zone (FAZ) areas in OCTA images in the superficial layer almost corresponded to those in FA images. The FAZ areas in the en-face OCT images in the superficial layer were smaller than those in the FA images and correlated with each other, which agreed with the ...

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    6. Choroidal changes observed with enhanced depth imaging optical coherence tomography in patients with mild Graves orbitopathy

      Choroidal changes observed with enhanced depth imaging optical coherence tomography in patients with mild Graves orbitopathy

      Purpose To evaluate the choroidal thickness in patients with Graves orbitopathy (GO) using enhanced depth imaging-optical coherence tomography (EDI-OCT). Methods Thirty-one patients with GO were evaluated prospectively. All subjects underwent ophthalmologic examination including best-corrected visual acuity, intraocular pressure measurement, biomicroscopic, and fundus examination. Choroidal thickness was measured at the central fovea. In addition, visual evoked potential measurement and visual field evaluation were performed. Results The mean choroidal thickness was 377.8±7.4   μ in the GO group, and 334±13.7   μ in the control group. (P = 0.004). There was a strong correlation between the choridal thickness and the clinical ...

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    7. Lens-based wavefront sensorless adaptive optics swept source OCT

      Lens-based wavefront sensorless adaptive optics swept source OCT

      Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high ...

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    8. Myopic Macular Retinoschisis in Teenagers: Clinical Characteristics and Spectral Domain Optical Coherence Tomography Findings

      Myopic Macular Retinoschisis in Teenagers: Clinical Characteristics and Spectral Domain Optical Coherence Tomography Findings

      To investigate the morphological characteristics of myopic macular retinoschisis (MRS) in teenagers with high myopia, six male (9 eyes) and 3 female (4 eyes) teenagers with typical MRS identified from chart review were evaluated. All cases underwent complete ophthalmic examinations including best corrected visual acuity (BCVA), indirect ophthalmoscopy, colour fundus photography, B-type ultrasonography, axial length measurement, and spectral-domain optical coherence tomography (SD-OCT). The average age was 17.8 ± 1.5 years, average refractive error was −17.04 ± 3.04D, average BCVA was 0.43 ± 0.61, and average axial length was 30.42 ± 1.71 mm. Myopic macular degenerative changes ...

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    9. Longitudinal, label-free, quantitative tracking of cell death and viability in a 3D tumor model with OCT

      Longitudinal, label-free, quantitative tracking of cell death and viability in a 3D tumor model with OCT

      Three-dimensional in vitro tumor models are highly useful tools for studying tumor growth and treatment response of malignancies such as ovarian cancer. Existing viability and treatment assessment assays, however, face shortcomings when applied to these large, complex, and heterogeneous culture systems. Optical coherence tomography (OCT) is a noninvasive, label-free, optical imaging technique that can visualize live cells and tissues over time with subcellular resolution and millimeters of optical penetration depth. Here, we show that OCT is capable of carrying out high-content, longitudinal assays of 3D culture treatment response. We demonstrate the usage and capability of OCT for the dynamic monitoring ...

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    10. Correlation of localized glaucomatous visual field defects and spectral domain optical coherence tomography retinal nerve fiber layer thinning using a modified structure–function map for OCT

      Correlation of localized glaucomatous visual field defects and spectral domain optical coherence tomography retinal nerve fiber layer thinning using a modified structure–function map for OCT

      Purpose To study the correlation between glaucomatous visual field (VF) defects assessed by standard automated perimetry (SAP) and peripapillary retinal nerve fiber layer (RNFL) thinning measured by spectral domain optical coherence tomography (OCT) using a modified OCT-based peripapillary RNFL structure–function map. Patients and methods Perimetric glaucoma patients and age-matched normal control subjects were recruited from a university hospital clinic. All eyes underwent testing with the Spectralis spectral domain OCT and SAP on the same day. An OCT-based correspondence map, which correlated VF areas with peripapillary RNFL sectors was created to evaluate the relationship between glaucomatous RNFL thinning and VF ...

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    11. An Elastic Second Skin

      An Elastic Second Skin

      We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss ...

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    12. Advances of optical coherence tomography in myopia and pathologic myopia

      Advances of optical coherence tomography in myopia and pathologic myopia

      The natural course of high-axial myopia is variable and the development of pathologic myopia is not fully understood. Advancements in optical coherence tomography (OCT) technology have revealed peculiar intraocular structures in highly myopic eyes and unprecedented pathologies that cause visual impairment. New OCT findings include posterior precortical vitreous pocket and precursor stages of posterior vitreous detachment; peripapillary intrachoroidal cavitation; morphological patterns of scleral inner curvature and dome-shaped macula. Swept source OCT is capable of imaging deeper layers in the posterior pole for investigation of optic nerve pits, stretched and thinned lamina cribrosa, elongated dural attachment at posterior scleral canal, and ...

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    13. Optical coherence tomography angiography in paracentral acute middle maculopathy secondary to central retinal vein occlusion

      Optical coherence tomography angiography in paracentral acute middle maculopathy secondary to central retinal vein occlusion

      Purpose To report the clinical course and the optical coherence tomography angiography (OCTA) findings of patients presenting with paracentral acute middle maculopathy (PAMM) and central retinal vein occlusion (CRVO). Methods Retrospective case series. Clincal records and multimodal imaging findings of patients presenting with PAMM and CRVO were reviewed. Results Three eyes of three patients (2 males; mean age: 66 years) were included in the study. Mean follow-up was 9 months and images using OCTA (AngioVue OCT angiography system, Optovue, Inc., Fremont, CA, USA) were available at the last follow-up visit. During follow-up, best corrected visual acuity (BCVA) of case 1 ...

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    14. Quantifying the influence of Bessel beams on image quality in optical coherence tomography

      Quantifying the influence of Bessel beams on image quality in optical coherence tomography

      Light scattered by turbid tissue is known to degrade optical coherence tomography (OCT) image contrast progressively with depth. Bessel beams have been proposed as an alternative to Gaussian beams to image deeper into turbid tissue. However, studies of turbid tissue comparing the image quality for different beam types are lacking. We present such a study, using numerically simulated beams and experimental OCT images formed by Bessel or Gaussian beams illuminating phantoms with optical properties spanning a range typical of soft tissue. We demonstrate that, for a given scattering parameter, the higher the scattering anisotropy the lower the OCT contrast, regardless ...

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    15. Contrast-enhanced optical coherence tomography with picomolar sensitivity for functional in vivo imaging

      Contrast-enhanced optical coherence tomography with picomolar sensitivity for functional in vivo imaging

      Optical Coherence Tomography (OCT) enables real-time imaging of living tissues at cell-scale resolution over millimeters in three dimensions. Despite these advantages, functional biological studies with OCT have been limited by a lack of exogenous contrast agents that can be distinguished from tissue. Here we report an approach to functional OCT imaging that implements custom algorithms to spectrally identify unique contrast agents: large gold nanorods (LGNRs). LGNRs exhibit 110-fold greater spectral signal per particle than conventional GNRs, which enables detection of individual LGNRs in water and concentrations as low as 250 pM in the circulation of living mice. This translates to ...

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    16. Predicting macular hole closure with ocriplasmin based on spectral domain optical coherence tomography

      Predicting macular hole closure with ocriplasmin based on spectral domain optical coherence tomography

      Purpose To assess the preoperative features of patients with idiopathic macular hole (IMH) and vitreomacular adhesion (VMA) treated with ocriplasmin (OCP) that can predict successful closure. Method Data were prospectively collected on all patients with IMH treated with OCP in three British ophthalmic centres. Several preoperative variables were recorded including the IMH base diameter (BD), minimum linear diameter (MLD), and VMA width measured on spectral domain optical coherence tomography. Several other IMH indices were derived including a ‘width factor’, defined as the BD minus the MLD in μm. The occurrence of VMA release and hole closure were used as the ...

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    17. In vivo cross-sectional imaging of the phonating larynx using long-range Doppler optical coherence tomography

      In vivo cross-sectional imaging of the phonating larynx using long-range Doppler optical coherence tomography

      Diagnosis and treatment of vocal fold lesions has been a long-evolving science for the otolaryngologist. Contemporary practice requires biopsy of a glottal lesion in the operating room under general anesthesia for diagnosis. Current in-office technology is limited to visualizing the surface of the vocal folds with fiber-optic or rigid endoscopy and using stroboscopic or high-speed video to infer information about submucosal processes. Previous efforts using optical coherence tomography (OCT) have been limited by small working distances and imaging ranges. Here we report the first full field, high-speed, and long-range OCT images of awake patients’ vocal folds as well as cross-sectional ...

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    18. Wide-field optical coherence tomography based microangiography for retinal imaging

      Wide-field optical coherence tomography based microangiography for retinal imaging

      Optical coherence tomography angiography (OCTA) allows for the evaluation of functional retinal vascular networks without a need for contrast dyes. For sophisticated monitoring and diagnosis of retinal diseases, OCTA capable of providing wide-field and high definition images of retinal vasculature in a single image is desirable. We report OCTA with motion tracking through an auxiliary real-time line scan ophthalmoscope that is clinically feasible to image functional retinal vasculature in patients, with a coverage of more than 60 degrees of retina while still maintaining high definition and resolution. We demonstrate six illustrative cases with unprecedented details of vascular involvement in retinal ...

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    19. Experimental Demonstration of Spectral Intensity Optical Coherence Tomography

      Experimental Demonstration of Spectral Intensity Optical Coherence Tomography

      We demonstrate experimentally spectral-domain intensity optical coherence tomography using a Mach-Zehnder interferometer with balanced detection. We show that the technique allows for a point spread function with reduced full-width at half maximum compared to conventional optical coherence tomography. The method further provides benefits similar to those of chirped-pulse interferometry in terms of dispersion cancellation but only requires a broadband incoherent source and standard detectors. The measurements are in excellent agreement with the theoretical predictions. Finally, we propose an approach that enables the elimination of potential artefacts arising from multiple interfaces

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    20. OCT-based label-free in vivo lymphangiography within human skin and areola

      OCT-based label-free in vivo lymphangiography within human skin and areola

      Due to the limitations of current imaging techniques, visualization of lymphatic capillaries within tissue in vivo has been challenging. Here, we present a label-free high resolution optical coherence tomography (OCT) based lymphangiography (OLAG) within human skin in vivo . OLAG enables rapid (~seconds) mapping of lymphatic networks, along with blood vessel networks, over 8 mm x 8 mm of human skin and 5 mm x 5 mm of human areola. Moreover, lymphatic system’s response to inflammation within human skin is monitored throughout an acne lesion development over 7 days. The demonstrated results promise OLAG as a revolutionary tool in the ...

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    21. Detection of preperimetric glaucoma using Bruch membrane opening, neural canal and posterior pole asymmetry analysis of optical coherence tomography

      Detection of preperimetric glaucoma using Bruch membrane opening, neural canal and posterior pole asymmetry analysis of optical coherence tomography

      We analysed retinal nerve fibre layer (RNFL) defects in eyes with normal circumpapillary RNFL (cpRNFL) thickness using posterior pole asymmetry analysis (PPAA) and investigated the parameters of Bruch membrane opening (BMO) and neural canals using enhanced depth imaging spectral domain optical coherence tomography (EDI-SDOCT). A total of 112 preperimetric glaucomatous eyes of 92 patients were examined to obtain cpRNFL thickness using SD-OCT. Posterior pole asymmetry analysis (PPAA) and central cross-sectional images of the optic nerve head (ONH) were obtained using EDI-SDOCT. Minimal and horizontal distances between the BMO and ONH surfaces (BMOM, BMOH) and the terminal of retinal pigment epithelium ...

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    22. Put innovation science at the heart of discovery : Nature News & Comment

      Put innovation science at the heart of discovery : Nature News & Comment

      I Innovation is being talked about everywhere. The US Senate is working on a biomedical innovation bill. Australia’s main funding agency has just announced that it will cut hundreds of climate scientists as part of its National Science and Innovation Agenda. The National Council of Science Museums in India will add Innovation Hubs at its centres. More and more organizations are using innovation in their names and brands. Innovation is a central plank of national and local policies and it consumes billions of dollars of investment worldwide. Yet the evidence base for these innovation efforts is close to nothing ...

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    23. Nanometer resolution optical coherence tomography using broad bandwidth XUV and soft x-ray radiation

      Nanometer resolution optical coherence tomography using broad bandwidth XUV and soft x-ray radiation

      Optical coherence tomography (OCT) is a non-invasive technique for cross-sectional imaging. It is particularly advantageous for applications where conventional microscopy is not able to image deeper layers of samples in a reasonable time, e.g. in fast moving, deeper lying structures. However, at infrared and optical wavelengths, which are commonly used, the axial resolution of OCT is limited to about 1  μ m, even if the bandwidth of the light covers a wide spectral range. Here, we present extreme ultraviolet coherence tomography (XCT) and thus introduce a new technique for non-invasive cross-sectional imaging of nanometer structures. XCT exploits the nanometerscale coherence ...

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    24. The design and validation of an optical coherence tomography-based classification system for focal vitreomacular traction

      The design and validation of an optical coherence tomography-based classification system for focal vitreomacular traction

      Purpose To develop and validate a classification system for focal vitreomacular traction (VMT) with and without macular hole based on spectral domain optical coherence tomography (SD-OCT), intended to aid in decision-making and prognostication. Methods A panel of retinal specialists convened to develop this system. A literature review followed by discussion on a wide range of cases formed the basis for the proposed classification. Key features on OCT were identified and analysed for their utility in clinical practice. A final classification was devised based on two sequential, independent validation exercises to improve interobserver variability. Results This classification tool pertains to idiopathic ...

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