1. All Articles

    1-24 of 20003 1 2 3 4 ... 832 833 834 »
    1. Free-Floating Pigmented Vitreous Cyst: Optical Coherence Tomography Findings

      Free-Floating Pigmented Vitreous Cyst: Optical Coherence Tomography Findings

      A 54-year-old woman presented with a chronic floater in the right eye. Dilated fundus examination revealed a pigmented free-floating vitreous cyst (Fig 1 A , Optos, Marlborough, MA). Saccades caused quick and fluid movements of the mobile sphere. Spectral-domain optical coherence tomography (SD OCT) (Fig 1 B , Spectralis; Heidelberg, Heidelberg, Germany) demonstrated a round, hyperreflective shell with hyporeflective contents. The lesion is anterior to the upper limit of the OCT and appears as a reflected image with shadowing of the underlying retina.

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    2. Micrometer-resolution in-fiber OCT probe with tunable working distance

      Micrometer-resolution in-fiber OCT probe with tunable working distance

      Optical coherence tomography (OCT) is an attractive modality in biomedical imaging systems due to its non-invasive imaging character. Since the image quality of OCT may be limited by the decrease of transverse resolution away from the focus spot, working distance tunable probe can be a strategy to overcome such limitation and maintain high transverse resolution at different imaging depths. In this paper, a miniature, working distance-tunable in-fiber OCT probe is demonstrated. The influences of the graded index fiber (GIF) length as well as the air cavity length on the working distance and the transverse resolution are simulated and discussed. Experimental ...

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    3. Angular compounding by full-channel B-scan modulation encoding for optical coherence tomography speckle reduction

      Angular compounding by full-channel B-scan modulation encoding for optical coherence tomography speckle reduction

      We describe an angular compounding method by full-channel B-scan modulation encoding for speckle reduction in optical coherence tomography. The complex-valued spectral interferogram (SI) is reconstructed by removing one of the conjugate terms in the depth space. Fourier transform of the complex SI along the lateral direction enables a full-channel (with both negative and positive Fourier space) for B-scan modulation in the spatial frequency ( ν ν ) domain. A full-size probe beam, determined by the scanning mirror size, is centered on the mirror pivot, which allows the negative and positive half-channels working in parallel. Compared with the existing method, where only a half-channel (negative ...

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    4. Calibration of optical coherence tomography angiography with a microfluidic chip

      Calibration of optical coherence tomography angiography with a microfluidic chip

      A microfluidic chip with microchannels ranging from 8 to 96    μ m 96  μm was used to mimic blood vessels down to the capillary level. Blood flow within the microfluidic channels was analyzed with split-spectrum amplitude-decorrelation angiography (SSADA)-based optical coherence tomography (OCT) angiography. It was found that the SSADA decorrelation value was related to both blood flow speed and channel width. SSADA could differentiate nonflowing blood inside the microfluidic channels from static paper. The SSADA decorrelation value was approximately linear with blood flow velocity up to a threshold V sat Vsat of 5.83 ± 1.33    mm / s 5.83 ...

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    5. Diagnosis of subglottic stenosis in a rabbit model using long-range optical coherence tomography

      Diagnosis of subglottic stenosis in a rabbit model using long-range optical coherence tomography

      Objectives/Hypothesis Current imaging modalities lack the necessary resolution to diagnose subglottic stenosis. The aim of this study was to use optical coherence tomography (OCT) to evaluate nascent subglottic mucosal injury and characterize mucosal thickness and structural changes using texture analysis in a simulated intubation rabbit model. Study Design Prospective animal study in rabbits. Methods Three-centimeter-long sections of endotracheal tubes (ETT) were endoscopically placed in the subglottis and proximal trachea of New Zealand White rabbits (n = 10) and secured via suture. OCT imaging and conventional endoscopic video was performed just prior to ETT segment placement (day 0), immediately after tube ...

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    6. Anterior segment optical coherence tomography of silicone oil keratopathy

      Anterior segment optical coherence tomography of silicone oil keratopathy

      A 77-year-old woman underwent pars plana vitrectomy for recurrent retinal detachment with silicone oil injection 10 years before presentation. Also the patient was placed on antiglaucoma medications. The patient had a history of recurrent corneal ulcerations in both eyes due to severe dry eyes. Examination revealed no light perception with a disfiguring central opaque corneal bulge in the left eye (figure 1). Anterior segment optical coherence tomography (OCT) revealed a marked thickening …

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    7. Common-path optical coherence tomography using a microelectromechanical-system-based endoscopic probe

      Common-path optical coherence tomography using a microelectromechanical-system-based endoscopic probe

      This paper presents a common-path (CP) swept-source optical coherence tomography (SSOCT) system based on a special endoscopic probe design with an in-line internal reflection as the reference and a two-axis electrothermal microelectromechanical system mirror for image scanning. The rear surface of a gradient reflective index (GRIN) lens inside the probe is set as the reference reflection plane. The length of the GRIN lens is optimized to eliminate the artifacts in SSOCT images successfully. Doppler OCT is also demonstrated based on the CP endoscopic probe. The diameter of the probe is only 2.5 mm, so it can be easily inserted ...

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    8. Filtering for unwrapping noisy Doppler optical coherence tomography images for extended microscopic fluid velocity measurement range

      Filtering for unwrapping noisy Doppler optical coherence tomography images for extended microscopic fluid velocity measurement range

      In this Letter, we report the first application of two phase denoising algorithms to Doppler optical coherence tomography (DOCT) velocity maps. When combined with unwrapping algorithms, significantly extended fluid velocity dynamic range is achieved. Instead of the physical upper bound, the fluid velocity dynamic range is now limited by noise level. We show comparisons between physical simulated ideal velocity maps and the experimental results of both algorithms. We demonstrate unwrapped DOCT velocity maps having a peak velocity nearly 10 times the theoretical measurement range.

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    9. Time-Series Interactions of Gene Expression, Vascular Growth and Hemodynamics during Early Embryonic Arterial Development

      Time-Series Interactions of Gene Expression, Vascular Growth and Hemodynamics during Early Embryonic Arterial Development

      The role of hemodynamic forces within the embryo as biomechanical regulators for cardiovascular morphogenesis, growth, and remodeling is well supported through the experimental studies. Furthermore, clinical experience suggests that perturbed flow disrupts the normal vascular growth process as one etiology for congenital heart diseases (CHD) and for fetal adaptation to CHD. However, the relationships between hemodynamics, gene expression and embryonic vascular growth are poorly defined due to the lack of concurrent, sequential in vivo data. In this study, a long-term, time-lapse optical coherence tomography (OCT) imaging campaign was conducted to acquire simultaneous blood velocity, pulsatile micro-pressure and morphometric data for ...

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      Mentions: Thorlabs
    10. Retinal and choroidal thicknesses measured with swept-source optical coherence tomography after surgery for idiopathic macular hole

      Retinal and choroidal thicknesses measured with swept-source optical coherence tomography after surgery for idiopathic macular hole

      To evaluate the changes in retinal nerve fiber layer thickness (RNFLT), ganglion cell layer thickness (GCLT), retinal thickness (RT), and subfoveal choroidal thickness (SFCT) in eyes that received pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling for idiopathic macular hole (IMH) and to compare these data with data from fellow eyes and healthy controls. This cross-sectional study included 49 subjects. Eighteen eyes that underwent surgery for IMH, 18 fellow eyes, and 31 eyes of the healthy controls were designated as group 1, group 2, and group 3, respectively. The RNFLT, GCLT, RT, and SFCT were measured by using ...

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    11. Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography

      Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography

      Objective The purpose of the study was to use the photonic imaging modality of optical coherence tomography (OCT) to compare the marginal adaptation of composite inlays fabricated by direct and indirect techniques. Material and Methods Class II cavities were prepared on 34 extracted human molar teeth. The cavities were randomly divided into two groups according to the inlay fabrication technique. The first group was directly restored on cavities with a composite (Esthet X HD, Dentsply, Germany) after isolating. The second group was indirectly restored with the same composite material. Marginal adaptations were scanned before cementation with an invisible infrared light ...

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      Mentions: Thorlabs
    12. A Case of Wyburn-Mason Syndrome with Facial Nevus Flammeus and the Associated Optical Coherence Tomography Findings

      A Case of Wyburn-Mason Syndrome with Facial Nevus Flammeus and the Associated Optical Coherence Tomography Findings

      Purpose To describe a case of Wyburn-Mason Syndrome, which is a rare phakomatosis, and its associated optical coherence tomography findings. Case summary A 5-year-old boy was referred to our clinic for decreased vision in his right eye. He had nevus flammeus on his right forehead, upper eyelid, and cheek. His best corrected visual acuity was hand motion in the right eye, in which a relative afferent pupillary defect was noted. Fundus examination of the right eye showed marked dilation and tortuosity of retinal vessels, which could not be discriminated between arteries and veins on the posterior pole. Optical coherence tomography ...

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    13. Optical Coherence Tomography Angiography in Mice: Comparison with Confocal Scanning Laser Microscopy and Fluorescein Angiography

      Optical Coherence Tomography Angiography in Mice: Comparison with Confocal Scanning Laser Microscopy and Fluorescein Angiography

      Purpose : Optical coherence tomography angiography (OCT-A) allows noninvasive visualization of retinal vessels in vivo. OCT-A was used to characterize the vascular network of the mouse retina and was compared with fluorescein angiography (FA) and histology. Methods : In the present study, OCT-A based on a Heidelberg Engineering Spectralis system was used to investigate the vascular network in mice. Data was compared with FA and confocal microscopy of flat-mount histology stained with isolectin IB4. For quantitative analysis the National Cancer Institute's AngioTool software was used. Vessel density, the number of vessel junctions, and endpoints were measured and compared between the imaging ...

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    14. Hybrid averaging offers high-flow contrast by cost apportionment among imaging time, axial, and lateral resolution in optical coherence tomography angiography

      Hybrid averaging offers high-flow contrast by cost apportionment among imaging time, axial, and lateral resolution in optical coherence tomography angiography

      The current temporal, wavelength, angular, and spatial averaging approaches trade imaging time and resolution for multiple independent measurements that improve the flow contrast in optical coherence tomography angiography (OCTA). We find that these averaging approaches are equivalent in principle, offering almost the same flow contrast enhancement as the number of averages increases. Based on this finding, we propose a hybrid averaging strategy for contrast enhancement by cost apportionment. We demonstrate that, compared with any individual approach, the hybrid averaging is able to offer a desired flow contrast without severe degradation of imaging time and resolution. Making use of the extended ...

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    15. Estimation of Jones matrix, birefringence and entropy using Cloude-Pottier decomposition in polarization-sensitive optical coherence tomography

      Estimation of Jones matrix, birefringence and entropy using Cloude-Pottier decomposition in polarization-sensitive optical coherence tomography

      Estimation of polarimetric parameters has been a fundamental issue to assess biological tissues that have form birefringence or polarization scrambling in polarization-sensitive optical coherence tomography (PS-OCT). We present a mathematical framework to provide a maximum likelihood estimation of the target covariance matrix and its incoherent target decomposition to estimate a Jones matrix of a dominant scattering mechanism, called Cloude-Pottier decomposition, thereby deriving the phase retardation and the optic axis of the sample. In addition, we introduce entropy that shows the randomness of the polarization property. Underestimation of the entropy at a low sampling number is mitigated by asymptotic quasi maximum ...

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    16. OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF THE FOVEAL MICROVASCULATURE IN GEOGRAPHIC ATROPHY

      OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF THE FOVEAL MICROVASCULATURE IN GEOGRAPHIC ATROPHY

      Purpose: To examine the retinal and choroidal foveal and parafoveal vasculature in patients with bilateral geographic atrophy (GA) secondary to age-related macular degeneration using optical coherence tomography angiography (OCTA). Methods: Fourteen eyes from 7 patients with and without fovea-sparing bilateral GA at St. Erik Eye Hospital. All patients were examined by optical coherence tomography angiography, en face OCT and fundus autofluorescence (FAF). Segmented optical coherence tomography angiography flow scans were obtained from the superficial retinal vascular layer (SL) and the choriocapillaris (CC) and correlated with areas of retinal pigment epithelial (RPE) loss on fundus autofluorescence. The foveal avascular zone (FAZ ...

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    17. Live volumetric (4D) visualization and guidance of in vivo human ophthalmic surgery with intraoperative optical coherence tomography

      Live volumetric (4D) visualization and guidance of in vivo human ophthalmic surgery with intraoperative optical coherence tomography

      Minimally-invasive microsurgery has resulted in improved outcomes for patients. However, operating through a microscope limits depth perception and fixes the visual perspective, which result in a steep learning curve to achieve microsurgical proficiency. We introduce a surgical imaging system employing four-dimensional (live volumetric imaging through time) microscope-integrated optical coherence tomography (4D MIOCT) capable of imaging at up to 10 volumes per second to visualize human microsurgery. A custom stereoscopic heads-up display provides real-time interactive volumetric feedback to the surgeon. We report that 4D MIOCT enhanced suturing accuracy and control of instrument positioning in mock surgical trials involving 17 ophthalmic surgeons ...

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    18. CHOROIDAL BLOOD FLOW VISUALIZATION IN HIGHLY MYOPIA USING A PROJECTION ARTIFACT METHOD IN OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

      CHOROIDAL BLOOD FLOW VISUALIZATION IN HIGHLY MYOPIA USING A PROJECTION ARTIFACT METHOD IN OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

      Purpose: To visualize choroidal blood flow in larger vessels in highly myopic eyes using a phenomenon of the projection artifact to in the sclera using optical coherence tomography angiography. Methods: The retrospective study included 92 eyes (54 patients) with greater than 8 diopters of myopia. All eyes were examined using optical coherence tomography angiography (RTVue XR Avanti; Optovue Inc, Fremont, CA). The blood flow in choroidal vessels was evaluated by attempting to directly segment the choroid and also by placing the segmentation layer behind the choroid, within the sclera. Subfoveal choroidal thickness was also measured at the same time. The ...

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    19. CLINICALLY INVISIBLE RETINAL HEMANGIOBLASTOMAS DETECTED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY AND FLUORESCEIN ANGIOGRAPHY IN TWINS

      CLINICALLY INVISIBLE RETINAL HEMANGIOBLASTOMAS DETECTED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY AND FLUORESCEIN ANGIOGRAPHY IN TWINS

      Purpose: To report subclinical retinal hemangioblastoma detected by enhanced depth imaging optical coherence tomography and fluorescein angiography in at-risk twins. Methods: Case report. Results: A set of twins, age 7 years, (Twin A and Twin B) with known family history of von Hippel-Lindau disease (gene test positive) and no systemic manifestations were evaluated. Visual acuity was 20/20 in both eyes of both twins. Anterior segment examination and intraocular pressures were unremarkable in both eyes. Twin A showed no clinically visible tumor in the right eye, and a clinically evident 4-mm hemangioblastoma in the superior retina of the left eye ...

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    20. Optical Coherence Tomography Angiography of Retinal Perfusion in Chiasmal Compression

      Optical Coherence Tomography Angiography of Retinal Perfusion in Chiasmal Compression

      BACKGROUND AND OBJECTIVE: To evaluate the retinal perfusion in patients with chiasmal compression using optical coherence tomography angiography (OCTA). PATIENTS AND METHODS: Retinal perfusion was evaluated using OCT angiograms in eight eyes of four patients with visual field (VF) defects due to chiasmal compression treated by tumor resection. The retinal perfusion in the area corresponding to the quadrants of the VF defects was investigated in each image. The vessel density was defined as the percentage area occupied by the vessels in the image. RESULTS: The decreased peripapillary retinal perfusion correlated with the quadrants of the VF defects on OCT angiograms ...

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    21. En Face Imaging of Epiretinal Membranes and the Retinal Nerve Fiber Layer Using Swept-Source Optical Coherence Tomography

      En Face Imaging of Epiretinal Membranes and the Retinal Nerve Fiber Layer Using Swept-Source Optical Coherence Tomography

      BACKGROUND AND OBJECTIVE: To describe en face swept-source optical coherence tomography (SS-OCT) imaging of epiretinal membranes (ERMs) and the underlying retinal nerve fiber layer (RNFL). PATIENTS AND METHODS: SS-OCT images were captured in nine eyes with ERMs. These SS-OCT en face images were qualitatively compared to spectral-domain OCT (SD-OCT) en face images. Using SS-OCT, en face images of the RNFL were obtained, if possible. RESULTS: En face SS-OCT images of ERMs were obtained in all nine eyes of eight individuals with clinically diagnosed ERMs that were superior to SD-OCT images. Clear en face images of the RNFL were acquired in ...

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    22. En Face Spectral-Domain Optical Coherence Tomography for the Diagnosis and Evaluation of Polypoidal Choroidal Vasculopathy

      En Face Spectral-Domain Optical Coherence Tomography for the Diagnosis and Evaluation of Polypoidal Choroidal Vasculopathy

      BACKGROUND AND OBJECTIVE: To evaluate the diagnostic capability of en face spectral-domain optical coherence tomography (SD-OCT) in patients with polypoidal choroidal vasculopathy (PCV) diagnosed by indocyanine green angiography (ICGA). PATIENTS AND METHODS: A retrospective, consecutive case series of 100 eyes diagnosed with PCV by ICGA were imaged with en face SD-OCT. Evaluation of the PCV complex on en face SD-OCT was performed on the ability to diagnose PCV by the characteristic configuration of the PCV complex and the extent and size of the PCV lesion. RESULTS: The PCV complex was better visualized on ICGA in 45 eyes, on en face ...

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    1-24 of 20003 1 2 3 4 ... 832 833 834 »
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