1. Articles in category: Ophthalmology

    1-24 of 8845 1 2 3 4 ... 367 368 369 »
    1. Multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography at 400 kHz

      Multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography at 400 kHz

      Multimodal imaging systems that combine scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) have demonstrated the utility of concurrent en face and volumetric imaging for aiming, eye tracking, bulk motion compensation, mosaicking, and contrast enhancement. However, this additional functionality trades off with increased system complexity and cost because both SLO and OCT generally require dedicated light sources, galvanometer scanners, relay and imaging optics, detectors, and control and digitization electronics. We previously demonstrated multimodal ophthalmic imaging using swept-source spectrally encoded SLO and OCT (SS-SESLO-OCT). Here, we present system enhancements and a new optical design that increase our SS-SESLO-OCT data throughput ...

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    2. Multi-volumetric registration and mosaicking using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

      Multi-volumetric registration and mosaicking using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

      Ophthalmic diagnostic imaging using optical coherence tomography (OCT) is limited by bulk eye motions and a fundamental trade-off between field-of-view (FOV) and sampling density. Here, we introduced a novel multi-volumetric registration and mosaicking method using our previously described multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and OCT (SS-SESLO-OCT) system. Our SS-SESLO-OCT acquires an entire en face fundus SESLO image simultaneously with every OCT cross-section at 200 frames-per-second. In vivo human retinal imaging was performed in a healthy volunteer, and three volumetric datasets were acquired with the volunteer moving freely and refixating between each acquisition. In post-processing, SESLO frames were used ...

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    3. Choroidal Blood Flow Visualization In High Myopia Using A Projection Artifact Method In Optical Coherence Tomography Angiography

      Choroidal Blood Flow Visualization In High 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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    4. Regarding optical coherence tomography grading of ischemia in central retinal venous occlusion

      Regarding optical coherence tomography grading of ischemia in central retinal venous occlusion

      The author read with interest the article by Browning et al. 1 The author humbly wants to discuss a few facts. 1. The article 1 discusses grading of retinal ischemia based on optical coherence tomography features in central retinal venous occlusion. As coexisting central retinal arterial occlusion or cilioretinal arterial occlusion may also cause inner retinal hyper-reflectivity, exclusion of such cases is an important consideration before implicating central retinal venous occlusion for the ischemia. Extensive intraretinal hemorrhages are other important hindrances to the evaluation of the perfusion status of the retina using both fluorescein angiogram and optical coherence tomography. 2 ...

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    5. Ultrahigh-resolution OCT imaging of the human cornea

      Ultrahigh-resolution OCT imaging of the human cornea

      We present imaging of corneal pathologies using optical coherence tomography (OCT) with high resolution. To this end, an ultrahigh-resolution spectral domain OCT (UHR-OCT) system based on a broad bandwidth Ti:sapphire laser is employed. With a central wavelength of 800 nm, the imaging device allows to acquire OCT data at the central, paracentral and peripheral cornea as well as the limbal region with 1.2 µm x 20 µm (axial x lateral) resolution at a rate of 140 000 A-scans/s. Structures of the anterior segment of the eye, not accessible with commercial OCT systems, are visualized. These include corneal ...

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    6. Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas

      Sub-micrometer axial resolution OCT for in-vivo imaging of the cellular structure of healthy and keratoconic human corneas

      Corneal degenerative conditions such as keratoconus (KC) cause progressive damage to the anterior corneal tissue and eventually severely compromise visual acuity. The ability to visualize corneal tissue damage in-vivo at cellular or sub-cellular level at different stages of development of KC and other corneal diseases, can aid the early diagnostics as well as the development of more effective treatment approaches for various corneal pathologies, including keratoconus. Here, we present the optical design of an optical coherence tomography system that can achieve 0.95 µm axial resolution in biological tissue and provide test results for the system’s spatial resolution and ...

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    7. Structural and functional human retinal imaging with a fiber-based visible light OCT ophthalmoscope

      Structural and functional human retinal imaging with a fiber-based visible light OCT ophthalmoscope

      The design of a multi-functional fiber-based Optical Coherence Tomography (OCT) system for human retinal imaging with < 2 micron axial resolution in tissue is described. A detailed noise characterization of two supercontinuum light sources with different pulse repetition rates is presented. The higher repetition rate and lower noise source is found to enable a sensitivity of 96 dB with 0.15 mW light power at the cornea and a 98 microsecond exposure time. Using a broadband (560 ± 50 nm), 90/10, fused single-mode fiber coupler designed for visible wavelengths, the sample arm is integrated into an ophthalmoscope platform, similar to current ...

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    8. Retinal oximetry in humans using visible-light optical coherence tomography [Invited]

      Retinal oximetry in humans using visible-light optical coherence tomography [Invited]

      We measured hemoglobin oxygen saturation (sO 2 ) in the retinal circulation in healthy humans using visible-light optical coherence tomography (vis-OCT). The measurements showed clear oxygenation differences between central retinal arteries and veins close to the optic nerve head. Spatial variations at different vascular branching levels were also revealed. In addition, we presented theoretical and experimental results to establish that noises in OCT intensity followed Rice distribution. We used this knowledge to retrieve unbiased estimation of true OCT intensity to improve the accuracy of vis-OCT oximetry, which had inherently lower signal-to-nose ratio from human eyes due to safety and comfort limitations ...

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    9. RETINAL LAYER SEGMENTATION AFTER SILICONE OIL OR GAS TAMPONADE FOR MACULA-ON RETINAL DETACHMENT USING OPTICAL COHERENCE TOMOGRAPHY

      RETINAL LAYER SEGMENTATION AFTER SILICONE OIL OR GAS TAMPONADE FOR MACULA-ON RETINAL DETACHMENT USING OPTICAL COHERENCE TOMOGRAPHY

      Purpose: To evaluate and compare the effect of silicone oil and gas on the thickness of all retinal layers in eyes with macula-on retinal detachment (RD). Methods: Three hundred and sixty-seven eyes of 367 patients who received silicone oil tamponade and 310 eyes of 310 patients who received gas tamponade for the treatment of rhegmatogenous RD were initially reviewed. Automated retinal segmentation method using Spectralis optical coherence tomography was used for analysis. The primary outcome measure was the change in thickness of each retinal layer in the central 1 mm zone (silicone oil vs. gas tamponade). The secondary outcome measure ...

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    10. Utility of optical coherence tomography in a case of bilateral congenital macular coloboma

      Utility of optical coherence tomography in a case of bilateral congenital macular coloboma

      Macular coloboma is a congenital defect of the retina and choroid in the macular region. It may appear due to an intrauterine inflammation or a developmental abnormality. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a result of malformation of the renal tubule. Its combination with ocular manifestations may be genetic, specifically in case of claudin‑19 (CLDN‑19) gene mutations. The combination of FHHNC and ocular manifestations is not always present in these patients. Optical coherence tomography (OCT) helps us diagnose this condition by allowing us to evaluate and confirm the absence of retina layers without histological examination. Although ...

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    11. Image-guided feedback for ophthalmic microsurgery using multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

      Image-guided feedback for ophthalmic microsurgery using multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

      Surgical interventions for ocular diseases involve manipulations of semi-transparent structures in the eye, but limited visualization of these tissue layers remains a critical barrier to developing novel surgical techniques and improving clinical outcomes. We addressed limitations in image-guided ophthalmic microsurgery by using microscope-integrated multimodal intraoperative swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (iSS-SESLO-OCT). We previously demonstrated in vivo human ophthalmic imaging using SS-SESLO-OCT, which enabled simultaneous acquisition of en face SESLO images with every OCT cross-section. Here, we integrated our new 400 kHz iSS-SESLO-OCT, which used a buffered Axsun 1060 nm swept-source, with a surgical microscope and ...

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    12. Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

      Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

      O ptical coherence tomography angiography (OCTA) is limited by projection artifacts from the superficial blood vessels onto deeper layers. We have recently described projection-resolved (PR) OCTA that solves the ambiguity between in situ flow and flow projection along each axial scan and suppresses the artifact on both en face and cross-sectional angiograms. While this method significantly improved the depth resolution of OCTA, the vascular integrity of the deeper layers was not fully preserved. In this study, we propose a novel reflectance-based projection-resolved (rbPR) OCTA algorithm which uses OCT reflectance to enhance the flow signal and suppress the projection artifacts in ...

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    13. Anterior segment imaging using non-invasive high-resolution optical coherence tomography

      Anterior segment imaging using non-invasive high-resolution optical coherence tomography

      One of the most important developments in the ophthalmology and visual sciences field has been the application of new techniques for imaging the anterior and posterior segment of the eye with non-contact devices. These techniques have been developed quickly considering that are non-invasive and provide high-resolution images of the different parts of the human eye. Definitely, the most spread and used technique for non-contact imaging of the human eye is the optical coherence tomography (OCT). OCT technique was first demonstrated in 1991 by Huang et al . (1). Based on low-coherence interferometry, OCT has become a prominent biomedical imaging technique with ...

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    14. Optical coherence tomography angiography of the optic disc; an overview

      Optical coherence tomography angiography of the optic disc; an overview

      Different diseases of the optic disc may be caused by or lead to abnormal vasculature at the optic nerve head. Optical coherence tomography angiography (OCTA) is a novel technology that provides high resolution mapping of the retinal and optic disc vessels. Recent studies have shown the ability of OCTA to visualize vascular abnormalities in different optic neuropathies. In addition, quantified OCTA measurements were found promising for differentiating optic neuropathies from healthy eyes.

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    15. Comparison of Anterior Segment Optical Coherence Tomography Bleb Grading, Moorfields Bleb Grading System, and Intraocular Pressure After Trabeculectomy

      Comparison of Anterior Segment Optical Coherence Tomography Bleb Grading, Moorfields Bleb Grading System, and Intraocular Pressure After Trabeculectomy

      PURPOSE To compare a novel anterior segment optical coherence tomography (AS-OCT) bleb grading system with a clinical bleb grading system and both with intraocular pressure (IOP) following trabeculectomy surgery. MATERIALS AND METHODS A novel AS-OCT grading system based on bleb size and internal reflectivity was developed. An imaging center was tasked with masked grading of AS-OCT images acquired by multiple surgical sites at postoperative week (POW) 2, postoperative month (POM) 4, 6, and 12, respectively. The Moorfields Bleb Grading System was used by another independent imaging center to grade clinical photos. The results of the 2 grading systems were compared ...

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    16. EVALUATION OF MACULAR ISCHEMIA IN EYES WITH BRANCH RETINAL VEIN OCCLUSION: An Optical Coherence Tomography Angiography Study

      EVALUATION OF MACULAR ISCHEMIA IN EYES WITH BRANCH RETINAL VEIN OCCLUSION: An Optical Coherence Tomography Angiography Study

      Purpose: To quantitatively assess macular morphology and perfusion status using optical coherence tomography, and optical coherence tomography angiography in eyes with branch retinal vein occlusion when macular edema has completely resolved, and to investigate the impact on visual function. Methods: Thirty consecutive eyes with branch retinal vein occlusion-macular edema that resolved after treatment with intravitreal ranibizumab injections were included. Macular sensitivity was measured by microperimetry; defect length of foveal ellipsoid zone band was measured using optical coherence tomography; foveal avascular zone and parafoveal nonperfusion areas (NPA) were measured by optical coherence tomography angiography. Results: The logarithm of minimum angle of ...

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    17. Evaluation of choroidal tumors with optical coherence tomography: enhanced depth imaging and OCT-angiography features

      Evaluation of choroidal tumors with optical coherence tomography: enhanced depth imaging and OCT-angiography features

      Aim To describe the vascular features of choroidal tumors using enhanced depth imaging (EDI), optical coherence tomography (OCT), and OCT-angiography. Methods In this prospective study, we evaluated 116 Caucasian patients with choroidal tumors (60 eyes with choroidal nevi, 40 with choroidal melanoma, 6 with choroidal hemangioma, 2 with optic disc melanocytoma, 6 with choroidal osteoma, and 2 with retinal metastases). Patients underwent a complete ophthalmic examination including bulbar echography, EDI-OCT, OCT-angiography, and multicolor imaging. Sixteen patients also underwent fluorescein and indocyanine angiography. Results The left eye was more involved than the right eye. The mean tumor thickness was 1.23 ...

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    18. Retinal Vessel Density in Optical Coherence Tomography Angiography in Optic Atrophy after Nonarteritic Anterior Ischemic Optic Neuropathy

      Retinal Vessel Density in Optical Coherence Tomography Angiography in Optic Atrophy after Nonarteritic Anterior Ischemic Optic Neuropathy

      Aims . To compare optical coherence tomography angiography (OCT-A) retinal vasculature measurements between normal and optic atrophy after nonarteritic anterior ischemic optic neuropathy (NAION) subjects. Design . This prospective observational study was conducted between July 2015 and August 2016 at the ophthalmology outpatient department of a referral center in Taiwan. Peripapillary (4.5 × 4.5 mm) and parafoveal (6 × 6 mm) OCT-A scans were acquired. Measurements of the peripapillary region were obtained in two areas: (1) circumpapillary vessel density (cpVD) and (2) whole enface image vessel density (wiVD). Results . 13 participants with optic atrophy after NAION had lower peripapillary vessel density than ...

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    19. Early microvascular retinal changes in optical coherence tomography angiography in patients with type 1 diabetes mellitus

      Early microvascular retinal changes in optical coherence tomography angiography in patients with type 1 diabetes mellitus

      Purpose Diabetic retinopathy (DR) can lead to significant vision loss and blindness and has a particularly high prevalence in patients with type 1 diabetes (DM1). In this study, we investigate quantitative differences in optical coherence tomography angiography (OCTA) data between DM1 patients with no or mild signs of retinopathy and non-diabetic subjects. Methods Optical coherence tomography angiography (OCTA) imaging was performed on DM1 patients with no or mild nonproliferative diabetic retinopathy and healthy, age-matched controls. Parafoveal vessel density and foveal avascular zone (FAZ) area in the deep capillary plexus (DCP) and superficial capillary plexus (SCP) were calculated with automated quantification ...

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    20. OCT imaging of retina useful in detecting glaucoma ‘masqueraders’

      OCT imaging of retina useful in detecting glaucoma ‘masqueraders’

      Optic nerve and macular optical coherence tomography can be helpful in distinguishing between glaucoma and glaucoma masqueraders, according to researchers. Researchers reported a case series of 4 patients and their spectral-domain OCT findings with retinal disease or nonglaucomatous optic neuropathy, who presented with suspected or previously diagnosed normal-tension glaucoma. The first patient was found to have marked diffuse retinal nerve fiber layer (RNFL) and macular thinning on OCT due to cancer-associated retinopathy, researchers wrote. The 76-year-old woman was referred after cataract surgery failed to relieve her symptoms of progressive vision loss. The second patient showed deep focal inferotemporal RNFL loss ...

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    21. History of Intraoperative OCT

      History of Intraoperative OCT

      Pars plana vitrectomy is almost a half-century old, and the earliest probes were powered by batteries, said Cynthia A. Toth, MD, the Joseph A.C. Wadsworth professor of ophthalmology at Duke University Medical Center. OCT imaging has “revolutionized our pre- and postoperative assessment,” she said, “but while our tools have advanced, our microscopes have not.” Although OCT granted surgeons the ability to visualize anatomical abnormalities in the retina, surgeons returned to en face OCT-free views during surgery. Dr. Toth noted there are “three staged developments in OCT – stage A was intraoperative OCT,” where a two-dimensional view outside the microscope gave ...

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    22. Retinal structure assessed by OCT as a biomarker of brain development in children born small for gestational age

      Retinal structure assessed by OCT as a biomarker of brain development in children born small for gestational age

      Purpose To identify differences in neuronal tissue from retinal and brain structures in children born small for gestational age (SGA) with no abnormality in neonatal brain ultrasonography and no previous neurological impairment, and to evaluate the relationship between retinal structure and brain changes in school-age children born SGA. Methods Two cohorts of children were recruited: 25 children born SGA and 25 children born with an appropriate birth weight according to gestational age. All the children underwent an ophthalmic examination, which included retinal imaging using spectral-domain optical coherence tomography, and a brain MRI. MRI images were automatically segmented and global and ...

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    23. Automated feature extraction for retinal vascular biometry in zebrafish using OCT angiography

      Automated feature extraction for retinal vascular biometry in zebrafish using OCT angiography

      Zebrafish have been identified as an ideal model for angiogenesis because of anatomical and functional similarities with other vertebrates. The scale and complexity of zebrafish assays are limited by the need to manually treat and serially screen animals, and recent technological advances have focused on automation and improving throughput. Here, we use optical coherence tomography (OCT) and OCT angiography (OCT-A) to perform noninvasive, in vivo imaging of retinal vasculature in zebrafish. OCT-A summed voxel projections were low pass filtered and skeletonized to create an en face vascular map prior to connectivity analysis. Vascular segmentation was referenced to the optic nerve ...

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