1. Articles from Robert J. Zawadzki

    49-72 of 96 « 1 2 3 4 »
    1. Multimodal assessment of microscopic morphology and retinal function in patients with geographic atrophy

      Multimodal assessment of microscopic morphology and retinal function in patients with geographic atrophy

      Purpose: To correlate retinal function and visual sensitivity with retinal morphology revealed by ultrahigh-resolution imaging with adaptive optics -optical coherence tomography (AO-OCT), on patients with geographic atrophy. Methods: Five eyes from five subjects were tested [4 with geographic atrophy (66.3 ± 6.4 years, mean±1S.D.) and 1 normal (61 years)]. Photopic and scotopic multifocal electroretinograms (mfERGs) were recorded. Visual fields were assessed with microperimetry (mP) combined with a scanning laser ophthalmoscope for high-resolution confocal retinal fundus imaging. The eye tracker of the microperimeter identified the preferred retinal locus that was then used as a reference for precise targeting ...

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    2. Adaptive optics optical coherence tomography for in vivo mouse retinal imaging

      Adaptive optics optical coherence tomography for in vivo mouse retinal imaging

      Small animal models of retinal diseases are important to vision research, and noninvasive high resolution in vivo rodent retinal imaging is becoming an increasingly important tool used in this field. We present a custom Fourier domain optical coherence tomography (FD-OCT) instrument for high resolution imaging of mouse retina. In order to overcome aberrations in the mouse eye, we incorporated a commercial adaptive optics system into the sample arm of the refractive FD-OCT system. Additionally, a commercially available refraction canceling lens was used to reduce lower order aberrations and specular back-reflection from the cornea. Performance of the adaptive optics (AO) system ...

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    3. FIVE-YEAR FOLLOW-UP OF MACULAR MORPHOLOGIC CHANGES AFTER RHEGMATOGENOUS RETINAL DETACHMENT REPAIR: Fourier Domain OCT Findings

      FIVE-YEAR FOLLOW-UP OF MACULAR MORPHOLOGIC CHANGES AFTER RHEGMATOGENOUS RETINAL DETACHMENT REPAIR: Fourier Domain OCT Findings

      Purpose: To evaluate serially long-term macular morphologic changes after successful macula-involving rhegmatogenous retinal detachment repair and correlate changes with macular function. Methods: Repeat Fourier domain optical coherence tomography (FD OCT) imaging and microperimetry (MP-1) testing of 8 of the initial cohort of 17 eyes studied 5 years earlier. Results: The mean follow-up after rhegmatogenous retinal detachment repair was 3.4 months (range, 1-8.5 months) for the first FD OCT and 5 years (range, 3.75-5.75 years) for the follow-up FD OCT. The final postoperative best-corrected visual acuity mean was 20/201 (range, 20/20 to counting fingers). Six ...

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    4. Visualization of human retinal and choroidal vascular networks with phase-variance optical coherence tomography

      Visualization of human retinal and choroidal vascular networks with phase-variance optical coherence tomography

      We present in vivo noninvasive retinal and choroidal perfusion maps with phase-variance optical coherence tomography (pvOCT). We acquired a pvOCT volumetric data set of a normal subject and visualized blood circulation in the retina and the choroid. En face projection views of the retina as well as the choroid were generated from a manually segmented volumetric data set. In addition, the processed pvOCT images were compared to current standard imaging modalities used for retinal and choroidal vasculature visualization in clinical settings, including fluorescein angiography (FA) and indocyanine green angiography (ICGA).

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    5. Application of full range swept source optical coherence tomography for imaging of the anterior eye segment in patients with type I Boston Keratoprosthesis

      Application of full range swept source optical coherence tomography for imaging of the anterior eye segment in patients with type I Boston Keratoprosthesis

      We present a high-speed complex conjugate resolved 1 μm swept source optical coherence tomography [SS-OCT] system using coherence revival of the light source for clinical imaging of the anterior segment of the eye. High-speed of 100,000 A-scans/sec and 1 μm imaging window of OCT permits dense 3D imaging of the anterior segment, minimizing the influence of motion artifacts and deep penetration of images for topographic analysis. The swept laser performance with internal clocking was adapted to achieve extended imaging depth requirements. The feasibility of our instrument for visualization of the anterior segment of patients with the Boston Keratoprosthesis ...

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    6. Development of a corneal tissue phantom for anterior chamber optical coherence tomography (AC-OCT)

      Development of a corneal tissue phantom for anterior chamber optical coherence tomography (AC-OCT)

      We document our latest work in developing a new eye model with a solid-state cornea and liquid filled anterior chamber designed for demonstrating, validating and comparing anterior chamber ophthalmic Optical Coherence Tomography (OCT) instruments, corneal topographers, and Scheimpflug cameras. Anterior chamber eye model (ACEM) phantoms can serve a variety of purposes, including demonstrating instrument functionality and performance in both the clinic and exhibit hall, validating corneal layer thickness measurements from different commercial instruments and as an aide for the R and D engineer and field service technician in the development and repair of instruments, respectively. The ideal eye model for ...

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    7. Complex conjugate artifact-free adaptive optics optical coherence tomography of in vivo human optic nerve head

      Complex conjugate artifact-free adaptive optics optical coherence tomography of in vivo human optic nerve head

      We acquired in vivo images of the human optic nerve head (ONH) using an adaptive optics—optical coherence tomography (AO-OCT) system. In order to improve imaging of the lamina cribrosa in the ONH with high lateral resolution and sensitivity, we implemented a complex conjugate artifact-free Fourier domain OCT (Fd-OCT) acquisition scheme with a reference arm-based phase shifting method. This allowed positioning of the lamina cribrosa structures near the zero path length difference where AO-OCT imaging achieves highest sensitivity. Implementation of our complex conjugate artifact removal (CCR) method required constant phase shifts between consecutive axial scans (A-scans), generated by continuous beam ...

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    8. Post-Doc Position for biomedical engineer / vision scientist in small animal High-Resolution Retinal Imaging group at University of California, Davis

      Post-Doc Position for biomedical engineer / vision scientist in small animal High-Resolution Retinal Imaging group at University of California, Davis

      Applications are invited for a post-doctoral research associate position in the UC Davis EyePod Laboratory in the Department of Cell biology and Human Anatomy at the UC Davis Main Campus. The goal of our research is to develop the next generation of in-vivo small animal cellular resolution multimodal retinal imaging instruments to study age-related changes in vision and retinal disorders. The ideal candidate will have strong skills in some combination of retinal/microscopic imaging modalities, including but not limited to AO, OCT, SLO, multispectral imaging, fluorescence, etc. Specifically, knowledge of programming languages (e.g. C++, LabView or Python) for maintaining ...

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    9. New Directions in Ophthalmic Optical Coherence Tomography

      New Directions in Ophthalmic Optical Coherence Tomography

      The rapid development of optical coherence tomography (OCT) and its ophthalmic applications has resulted in the emergence of new laboratory and commercial systems that vary in performance and functionality. The introduction of high-speed imaging capabilities has abrogated the primary limitation of early OCT technology by providing in vivo three-dimensional volumetric reconstructions of both anterior and posterior segments of the human eye within reasonable time constraints. Currently, high-speed swept source OCT technology has made it possible to achieve OCT acquisition speeds of several million A-scans/s. Another direction of OCT development includes the introduction of adaptive optics to imaging of the ...

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    10. In-vivo imaging of inner retinal cellular morphology with adaptive optics-optical coherence tomography: challenges and possible solutions

      In-vivo imaging of inner retinal cellular morphology with adaptive optics-optical coherence tomography: challenges and possible solutions

      Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the outer layers of the human retina. Despite the significant progress in imaging cone and rod photoreceptor mosaics, visualization of cellular structures in the inner retina has been achieved only with extrinsic contrast agents that have not been approved for use with humans. In this paper we describe the main limiting factors in visualizing inner retinal cells and the ...

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    11. New developments in eye models with retina tissue phantoms for ophthalmic optical coherence tomography

      New developments in eye models with retina tissue phantoms for ophthalmic optical coherence tomography

      We document our latest work in developing eye models with solid-state retinal tissue phantoms designed for demonstrating, validating and comparing ophthalmic Optical Coherence Tomography (OCT) instruments. Eye models with retina tissue phantoms can serve a variety of purposes, including demonstrating OCT functionality and performance in both the clinic and exhibit hall, validating retina layer thickness measurements from different commercial OCT instruments and as an aide for the R&D engineer and field service technician in the development and repair of instruments, respectively. The ideal eye model for OCT, the optical cross-sectional imaging modality, would have a volumetric morphology and scattering ...

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    12. Visualization of human retinal capillary networks: a comparison of intensity, speckle-variance and phase-variance optical coherence tomography

      Visualization of human retinal capillary networks: a comparison of intensity, speckle-variance and phase-variance optical coherence tomography

      We evaluate methods to visualize human retinal micro-circulation in vivo by standard intensity-based optical coherence tomography (OCT), speckle-variance optical coherence tomography (svOCT), and phase-variance optical coherence tomography (pvOCT). En face projection views created from the same volumetric data set of the human retina using all three data processing methods are created and compared. Additionally we used support vector machine (SVM) based semi-automatic segmentation to generate en face projection views of individual retinal layers. The layers include: first, the whole inner retina (from the nerve fiber layer to the outer nuclear layer), and second, from the ganglion cell layer to the ...

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    13. Noninvasive Imaging of the Foveal Avascular Zone with High-Speed, Phase-Variance Optical Coherence Tomography

      Noninvasive Imaging of the Foveal Avascular Zone with High-Speed, Phase-Variance Optical Coherence Tomography

      Purpose. To demonstrate the application of phase-variance optical coherence tomography (pvOCT) for contrast agent–free in vivo imaging of volumetric retinal microcirculation in the human foveal region and for extraction of foveal avascular zone dimensions. Methods. A custom-built, high-speed Fourier-domain OCT retinal imaging system was used to image retinas of two healthy subjects and eight diabetic patients. Through the acquisition of multiple B-scans for each scan location, phase differences between consecutive scans were extracted and used for phase-variance contrast, identifying motion signals from within blood vessels and capillaries. The en face projection view of the inner retinal layers segmented out ...

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    14. Performance of 97-elements ALPAO membrane magnetic deformable mirror in Adaptive Optics - Optical Coherence Tomography system for in vivo imaging of human retina

      Performance of 97-elements ALPAO membrane magnetic deformable mirror in Adaptive Optics - Optical Coherence Tomography system for in vivo imaging of human retina
      We present an evaluation of two different configurations of the ALPAO 97-actuator membrane magnetic deformable mirror for wavefront correction, using either 7 or 9 actuators across the eye pupil. These tests included monitoring of aberration correction for a human subject. This AO-sub system is part of the UC Davis high-resolution human retinal imaging adaptive optics - optical coherence tomography (AO-OCT) instrument. AO-OCT allows the three-dimensional (3D) visualization of different retinal structures in vivo with high volumetric resolution (3x3x3µm3). Full Text: PDF References: [1] R.J. Zawadzki, S. Jones, S. Olivier, M. Zhao, B. Bower, J. Izatt, S. Choi, S. Laut, and ...
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    15. Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging

      Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging
      , , , , , , We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was ... [Biomed. Opt. Express 2, 1674-1686 (2011)]
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    16. In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography

      In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography
      We present in vivo volumetric images of human retinal micro-circulation using Fourier-domain optical coherence tomography (Fd-OCT) with the phase-variance based motion contrast method. Currently fundus fluorescein angiography (FA) is the standard technique in clinical settings for visualizing blood circulation of the retina. High contrast imaging of retinal vasculature is achieved by injection of a fluorescein dye into the systemic circulation. We previously reported phase-variance optical coherence tomography (pvOCT) as an alternative and non-invasive technique to image human retinal capillaries. In contrast to FA, pvOCT allows not only noninvasive visualization of a two-dimensional retinal perfusion map but also volumetric morphology of ...
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    17. AO-OCT with reference arm phase shifting for complex conjugate artifact-free imaging of in vivo retinal structures

      AO-OCT with reference arm phase shifting for complex conjugate artifact-free imaging of in vivo retinal structures

      We summarize the performance of an AO-OCT system with reference arm phase shifting for complex conjugate artifactfree imaging of in vivo retinal structures. As a complex conjugate artifact removal (CCR) method we used a previously reported technique requiring constant phase shifts between consecutive A-scans. In our system these shifts were generated by continuous beam path-length changes from offsetting the pivot point of the scanning mirror placed in the system reference arm. In order to reconstruct the complex spectral fringe pattern we used Fourier transformation along the transverse axis and a filtering algorithm. The suppression ratio of mirror complex artifact images ...

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    18. Visualization of human retinal micro-capillaries with phase contrast high-speed optical coherence tomography

      Visualization of human retinal micro-capillaries with phase contrast high-speed optical coherence tomography

      We present high-speed Fourier-domain optical coherence tomography (Fd-OCT) with the phase variance based motion contrast method for visualizing retinal micro-circulation in vivo. This technique allows non-invasive visualization of a two-dimensional retinal perfusion map and concurrent volumetric morphology of retinal microvasculature with high sensitivity. The high-speed acquisition rate at 125kHz A-scans enables reduction of motion artifacts with increased scanning area if compared to previously reported results. Several scanning schemes with different sampling densities and scanning areas are evaluated to find optimal parameters for in vivo imaging. In order to evaluate this technique, we compare OCT micro-capillary imaging using the phase variance ...

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    19. Evidence of outer retinal changes in glaucoma patients as revealed by ultrahigh-resolution in vivo retinal imaging

      Evidence of outer retinal changes in glaucoma patients as revealed by ultrahigh-resolution in vivo retinal imaging
      Aims It is well established that glaucoma results in a thinning of the inner retina. To investigate whether the outer retina is also involved, ultrahigh-resolution retinal imaging techniques were utilised. Methods Eyes from 10 glaucoma patients (25–78 years old), were imaged using three research-grade instruments: (1) ultrahigh-resolution Fourier-domain optical coherence tomography (UHR-FD-OCT), (2) adaptive optics (AO) UHR-FD-OCT and (3) AO-flood illuminated fundus camera (AO-FC). UHR-FD-OCT and AO-UHR-FD-OCT B-scans were examined for any abnormalities in the retinal layers. On some patients, cone density measurements were made from the AO-FC en face images. Correlations between retinal structure and visual sensitivity were ...
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    20. Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography

      Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography
      Single spectrometer-based complex conjugate artifact removal methods are evaluated for in vivo imaging with complementary metal-oxide semiconductor line scan camera based high-speed Fourier-domain optical coherence tomography (FD–OCT) at 100,000 axial scans per second. Performance of three different phase-shifting methods with the same OCT engine is evaluated using modified data acquisition schemes, depending on the requirements of each phase-shifting technique. The suppression ratio of complex conjugate artifact images using a paperboard is assessed for all tested methods. Several other characteristics, including a list of additional hardware requirements (beyond standard FD-OCT components) and data acquisition schemes for each of the ...
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    21. High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography

      High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography
      This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.
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    22. High-Resolution Fourier-Domain Optical Coherence Tomography of Choroidal Neovascular Membranes Associated with Age-Related Macular Degeneration

      High-Resolution Fourier-Domain Optical Coherence Tomography of Choroidal Neovascular Membranes Associated with Age-Related Macular Degeneration
      High-resolution Fourier-domain optical coherence tomography (Fd-OCT) provided visualization of choroidal neovascular membrane (CNVM) and associated morphologic changes in the retina in eyes with neovascular age-related macular degeneration. The growth pattern and size of CNVM was determined with Fd-OCT and correlated better with findings on fluorescein angiography in eyes with classic lesions.
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    23. Maculopathy Diagnosed With High-Resolution Fourier-Domain Optical Coherence Tomography in Eyes With Previously Unexplained Visual Loss

      Maculopathy Diagnosed With High-Resolution Fourier-Domain Optical Coherence Tomography in Eyes With Previously Unexplained Visual Loss
      Purpose: To describe maculopathy diagnosed with high-resolution Fourier-domain optical coherence tomography among eyes with previously unexplained visual loss. Methods: Nine eyes from six patients with previously unexplained vision loss based on funduscopy, fluorescein angiography, and Stratus optical coherence tomography and 32 eyes from 25 asymptomatic age-matched control subjects were imaged with a Fourier-domain optical coherence tomography instrument with axial resolution of 4 [mu]m to 4.5 [mu]m and transverse resolution of 10 [mu]m to 15 [mu]m. Results: Among eyes with unexplained vision loss, visual acuity ranged from 20/20 to 20/80 and central scotoma was ...
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    49-72 of 96 « 1 2 3 4 »
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    Evaluation of complex conjugate artifact removal methods used in spectrometer-based Fourier-domain optical coherence tomography systems - a comparative study In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography Feature Of The Week 02/01/2015: Progress on Developing Adaptive Optics OCT for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts (with Audio Narration) Swept Source Optical Coherence Tomography in Ocular Diseases Special Interest Group at ARVO Post-Doc Position for biomedical engineer / vision scientist in the UC Davis EyePod - Small Animal Retinal Imaging Laboratory at University of California, Davis Post-Doc Position for Biomedical Engineer / Vision Scientist in the UC Davis EyePod - Small Animal Retinal Imaging Laboratory at University of California, Davis Optoretinography: optical measurements of human cone and rod photoreceptor responses to light Nodular skin lesions: correlation of reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) features OCT and Ophthalmology in the Age of Artificial Intelligence, Tuesday Oct 8, 2019 1:00P EDT Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography Pattern electroretinogram changes in patients with primary open-angle glaucoma in correlation with visual field and optical coherence tomography changes Objective evaluation of proliferative diabetic retinopathy using optical coherence tomography