1. Articles from Robert J. Zawadzki

    25-48 of 92 « 1 2 3 4 »
    1. Progress on developing wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      Progress on developing wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      We present a new design for a wavefront sensorless adaptive optics (WS-AO) Fourier domain optical coherence tomography (FD-OCT) system for small animal retinal imaging in vivo. Without the optical complications necessary for inclusion of a wavefront sensor in the optical system, this version of WS-AO FD-OCT system has a simplified optical design, including elimination of long focal length scanning optics and optical conjugation of vertical and horizontal scanners. This modification provides a modular large Field of View for retinal screening (25 degree visual angle), while also allowing a “zoom” capability for allocating all the scanning resources to a smaller region ...

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    2. Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging

      Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging

      A compact, non-invasive multi-modal system has been developed for in vivo mouse retina imaging. It is configured for simultaneously detecting green and red fluorescent protein signals with scanning laser ophthalmoscopy (SLO) back-scattered light from the SLO illumination beam, and depth information about different retinal layers by means of Optical Coherence Tomography (OCT). Simultaneous assessment of retinal characteristics with different modalities can provide a wealth of information about the structural and functional changes in the retinal neural tissue and chorio-retinal vasculature in vivo. Additionally, simultaneous acquisition of multiple channels facilitates analysis of the data of different modalities by automatic temporal and ...

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    3. Performance of a combined optical coherence tomography and scanning laser ophthalmoscope with adaptive optics for human retinal imaging application

      Performance of a combined optical coherence tomography and scanning laser ophthalmoscope with adaptive optics for human retinal imaging application

      We describe the design and performance of a recently implemented retinal imaging system for the human eye that combines adaptive optics (AO) with spectral domain optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO). The AO-OCT-SLO system simultaneously acquires SLO frames and OCT B-scans at 60 Hz with an OCT volume acquisition scan rate of 0.24 Hz. The SLO images are used to correct for eye motion during the registration of OCT B-scans. Key optical design considerations are discussed including: minimizing system aberrations through the use of off-axis relay telescopes; choice of telescope magnification based on pupil plane requirements ...

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    4. 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)

      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)

      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 human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image, complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking ...

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    5. In vivo imaging of human photoreceptor mosaic with wavefront sensorless adaptive optics optical coherence tomography

      In vivo imaging of human photoreceptor mosaic with wavefront sensorless adaptive optics optical coherence tomography

      Wavefront sensorless adaptive optics optical coherence tomography (WSAO-OCT) is a novel imaging technique for in vivo high-resolution depth-resolved imaging that mitigates some of the challenges encountered with the use of sensor-based adaptive optics designs. This technique replaces the Hartmann Shack wavefront sensor used to measure aberrations with a depth-resolved image-driven optimization algorithm, with the metric based on the OCT volumes acquired in real-time. The custom-built ultrahigh-speed GPU processing platform and fast modal optimization algorithm presented in this paper was essential in enabling real-time, in vivo imaging of human retinas with wavefront sensorless AO correction. WSAO-OCT is especially advantageous for developing ...

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    6. Progress on Developing Adaptive Optics-Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      Progress on Developing Adaptive Optics-Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      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 human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image , complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking ...

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    7. In vivo imaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1-μm swept-source optical coherence tomography

      In vivo imaging of human vasculature in the chorioretinal complex using phase-variance contrast method with phase-stabilized 1-μm swept-source optical coherence tomography

      We present a noninvasive phase-variance (pv)–based motion contrast method for depth-resolved imaging of the human chorioretinal complex microcirculation with a newly developed phase-stabilized high speed (100-kHz A-scans/s) 1 - μ m swept-source optical coherence tomography (SSOCT) system. Compared to our previous spectral-domain (spectrometer based) pv-spectral domain OCT (SDOCT) system, this system has the advantages of higher sensitivity, reduced fringe wash-out for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization ...

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    8. The cellular origins of the outer retinal bands in optical coherence tomography images

      The cellular origins of the outer retinal bands in optical coherence tomography images

      Purpose: To test the recently proposed hypothesis that the second OCT outer retinal band originates from the inner segment ellipsoid, by measuring: 1) thickness of this band within single cones, and 2) its respective distance from the external limiting membrane and outer segment tips. Methods: Adaptive optics OCT images were obtained from four normal subjects. Images were obtained at foveal (2∘) and perifoveal (5∘) locations. Cones (n = 9593) were identified and segmented in three dimensions using custom software. Features corresponding to bands 1, 2, and 3 were automatically identified. Thickness of band 2 was assessed in each cell by fitting ...

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    9. 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 Small Animal Imaging 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 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 adaptive optics (AO), OCT, SLO, multispectral imaging, fluorescence, etc. Knowledge of programming languages (e.g. C++, LabView ...

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    10. Evaluation of OCT for quantitative in-vivo measurements of changes in neural tissue scattering in longitudinal studies of retinal degeneration in mice

      Evaluation of OCT for quantitative in-vivo measurements of changes in neural tissue scattering in longitudinal studies of retinal degeneration in mice

      Optical coherence tomography is an imaging modality that is broadly used in ophthalmic diagnostics. The current generation of OCT systems enables reliable acquisition of volumetric scans containing information about the thicknesses of the various retinal layers. Thus, monitoring layer thickness changes is the main quantitative analysis performed by commercial instruments. In principle, measurements of the OCT signal intensity could also provide information on the health status of the retinal tissue. Unfortunately quantitative measurements and interpretation of scattering changes in retinal OCT is very limited due to variation in overall brightness of the OCT B-scans between imaging sessions. These changes might ...

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    11. Improved in vivo imaging of human blood circulation in the chorioretinal complex using phase variance method with new phase stabilized 1 μm swept-source optical coherence tomography (pv-SSOCT)

      Improved in vivo imaging of human blood circulation in the chorioretinal complex using phase variance method with new phase stabilized 1 μm swept-source optical coherence tomography (pv-SSOCT)

      We demonstrate the feasibility of our newly developed phase stabilized high-speed (100 kHz A-scans/s) 1 μm sweptsource optical coherence tomography (SSOCT) system with the phase-variance based motion contrast method for visualization of human chorioretinal complex microcirculation. Compared to our previously reported spectral domain (spectrometer based) phase-variance (pv)-SDOCT system it has advantages of higher sensitivity, reduced fringe washout for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization method ...

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    12. Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      e present wavefront sensorless adaptive optics (WSAO) Fourier domain optical coherence tomography (FD-OCT) for in vivo small animal retinal imaging. WSAO is attractive especially for mouse retinal imaging because it simplifies optical design and eliminates the need for wavefront sensing, which is difficult in the small animal eye. GPU accelerated processing of the OCT data permitted real-time extraction of image quality metrics (intensity) for arbitrarily selected retinal layers to be optimized. Modal control of a commercially available segmented deformable mirror (IrisAO Inc.) provided rapid convergence using a sequential search algorithm. Image quality improvements with WSAO OCT are presented for both ...

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    13. The Dose-Dependent Macular Thickness Changes Assessed By FD-OCT in Patients With Retinitis Pigmentosa Treated With Ciliary Neurotrophic Factor

      The Dose-Dependent Macular Thickness Changes Assessed By FD-OCT in Patients With Retinitis Pigmentosa Treated With Ciliary Neurotrophic Factor

      Purpose: To evaluate the effect of intravitreal ciliary neurotrophic factor (CNTF) implant on mean macular thickness (MMT) in eyes with retinitis pigmentosa using high-resolution Fourier domain optical coherence tomography imaging. Methods: A cohort of 8 patients (CNTF-3: n = 5; CNTF-4: n = 3) enrolled in Neurotech sponsored Phase 2 clinical trial underwent Fourier domain optical coherence tomography imaging. A >=3% change in MMT from baseline or fellow eye was considered as a measurable change. Results: Two patients enrolled in the CNTF-3 study received low-dose implant. At 18 months, a change in MMT from -4.47 [mu]m to 6 [mu]m ...

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    14. Progress on Developing Adaptive Optics–Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      Progress on Developing Adaptive Optics–Optical Coherence Tomography for In Vivo Retinal Imaging: Monitoring and Correction of Eye Motion Artifacts

      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 human retina. Here, we present a short review of progress on developing AO-OCT instruments. Despite significant progress in imaging speed and resolution, eye movements present during acquisition of a retinal image with OCT introduce motion artifacts into the image, complicating analysis and registration. This effect is especially pronounced in high-resolution datasets acquired with AO-OCT instruments. Several retinal tracking ...

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    15. Phase-Variance Optical Coherence Tomography: A New Technique for Noninvasive Angiography

      Phase-Variance Optical Coherence Tomography: A New Technique for Noninvasive Angiography

      Purpose Phase-variance optical coherence tomography (PV-OCT) provides volumetric imaging of the retinal vasculature without the need for intravenous injection of a fluorophore. We compare images from PV-OCT and fluorescein angiography (FA) for normal individuals and patients with age-related macular degeneration (AMD) and diabetic retinopathy. Design This is an evaluation of a diagnostic technology. Participants Four patients underwent comparative retinovascular imaging using FA and PV-OCT. Imaging was performed on 1 normal individual, 1 patient with dry AMD, 1 patient with exudative AMD, and 1 patient with nonproliferative diabetic retinopathy. Methods Fluorescein angiography imaging was performed using a Topcon Corp (Tokyo, Japan ...

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    16. Improved visualization of outer retinal morphology with aberration cancelling reflective optical design for adaptive optics - optical coherence tomography

      Improved visualization of outer retinal morphology with aberration cancelling reflective optical design for adaptive optics - optical coherence tomography

      We present an aberration cancelling optical design for a reflective adaptive optics - optical coherence tomography (AO-OCT) retinal imaging system. The optical performance of this instrument is compared to our previous multimodal AO-OCT/AO-SLO retinal imaging system. The feasibility of new instrumentation for improved visualization of microscopic retinal structures is discussed. Examples of images acquired with this new AO-OCT instrument are presented.

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    17. Three-dimensional anterior segment imaging in patients with type 1 Boston Keratoprosthesis with switchable full depth range swept source optical coherence tomography

      Three-dimensional anterior segment imaging in patients with type 1 Boston Keratoprosthesis with switchable full depth range swept source optical coherence tomography

      A high-speed (100 kHz A - scans / s ) complex conjugate resolved 1 μ m swept source optical coherence tomography (SS-OCT) system using coherence revival of the light source is suitable for dense three-dimensional (3-D) imaging of the anterior segment. The short acquisition time helps to minimize the influence of motion artifacts. The extended depth range of the SS-OCT system allows topographic analysis of clinically relevant images of the entire depth of the anterior segment of the eye. Patients with the type 1 Boston Keratoprosthesis (KPro) require evaluation of the full anterior segment depth. Current commercially available OCT systems are not suitable for ...

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    18. Optical imaging of the chorioretinal vasculature in the living human eye

      Optical imaging of the chorioretinal vasculature in the living human eye

      Detailed visualization of microvascular changes in the human retina is clinically limited by the capabilities of angiography imaging, a 2D fundus photograph that requires an intravenous injection of fluorescent dye. Whereas current angiography methods enable visualization of some retinal capillary detail, they do not adequately reveal the choriocapillaris or other microvascular features beneath the retina. We have developed a noninvasive microvascular imaging technique called phase-variance optical coherence tomography (pvOCT), which identifies vasculature three dimensionally through analysis of data acquired with OCT systems. The pvOCT imaging method is not only capable of generating capillary perfusion maps for the retina, but it ...

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    19. Feature Of The Week 6/16/13: Using Adaptive Optics Optical Coherence Tomography for in vivo Mouse Retinal Imaging

      Feature Of The Week 6/16/13: Using Adaptive Optics Optical Coherence Tomography for in vivo Mouse Retinal Imaging

      Small animal models of human diseases serve as a vital component in modern medical research, including eye-related research, where they facilitate the understanding of the underlying biological processes of human disorders, and development of novel therapies against vision-robbing diseases. Non-invasive ophthalmic imaging modalities such as optical coherence tomography have become an important tool for small animal vision research programs and has greatly accelerated numerous preclinical studies. OCT offers the ability to perform longitudinal in vivo studies which are not feasible with more invasive imaging techniques such as immunohistology. However, to better visualize the retinal cellular microstructure and understand the molecular ...

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    20. Staging of Macular Telangiectasia: Power-Doppler Optical Coherence Tomography and Macular Pigment Optical Density

      Staging of Macular Telangiectasia: Power-Doppler Optical Coherence Tomography and Macular Pigment Optical Density

      Purpose: Two methods were used to study the stages of macular telangiectasia (MacTel): Power-Doppler optical coherence tomography (PD-OCT) which allows imaging of retinal circulation in three-dimensions, and macular pigment optical density (MPOD) which quantifies the distribution of macular carotenoids. Methods: Among 49 patients with MacTel identified, 12 eyes (6 patients) with MacTel and 7 age-matched control eyes (7 patients) were imaged with a custom-built Fourier-domain OCT instrument to acquire PD-OCT images. MPOD was measured using heterochromatic flicker photometry in 10 eyes (5 patients) with MacTel and compared to 44 age-matched control eyes (44 patients). Clinical staging of MacTel was based ...

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    21. 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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    22. 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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    23. 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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    24. 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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    25-48 of 92 « 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 PhD Student and Postdoctoral Associate Positions at the University of Massachusetts Early Detection of Microvascular Changes in Patients with Diabetes Mellitus without and with Diabetic Retinopathy: Comparison between Different Swept-Source OCT-A Instruments In vivo tomographic visualization of intracochlear vibration using a supercontinuum multifrequency-swept optical coherence microscope A Simple Algorithm for Hard Exudate Detection in Diabetic Retinopathy Using Spectral-Domain Optical Coherence Tomography Optical coherence tomography analysis of the recovery of the ellipsoid zone after macular hole surgery: 2-Year results Anterior Segment Applications of Optical Coherence Tomography Angiography