1. Articles from David Huang

    193-216 of 237 « 1 2 3 4 5 6 7 8 9 10 »
    1. Normal and keratoconic corneal epithelial thickness mapping using Fourier-domain optical coherence tomography

      Normal and keratoconic corneal epithelial thickness mapping using Fourier-domain optical coherence tomography

      The detection of early-stage keratoconus is one of the most important safety issues in screening candidates for corneal refractive surgeries. We propose to use epithelial thickness maps to assist the diagnosis of keratoconus. The corneal epithelial thickness in normal and keratoconic eyes was mapped with optical coherence tomography (OCT). A Fourier-domain OCT system capable of acquiring 26,000 axial-scans per second was used. It has an axial resolution of 5μm in cornea. A pachymetry scan pattern (8 radials, 1024 axial-scans each, 6mm diameter, repeat 3 times) centered at the pupil center was used to image the cornea. The 3 repeated ...

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    2. Dual angle scan protocol with Doppler optical coherence tomography for retinal blood flow measurement

      Dual angle scan protocol with Doppler optical coherence tomography for retinal blood flow measurement

      To improve the scan quality of Doppler Optical coherence tomography for blood flow measurement, we investigate how to improve the Doppler signal for all vessels around optic disc. Doppler signal is depending on the Doppler angle, which is defined as angle between OCT beams and normal direction vessel. In this examination, we test the effect of different OCT beam direction on Doppler angles of all veins. We also test maximizing the Doppler angle by combining scans with different OCT beams direction. Three criteria were used to evaluate the overall quality, average Doppler angle, the percentage of vessels with Doppler angle ...

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    3. Effect of blood vessel diameter on relative blood flow estimate in Doppler optical coherence tomography algorithms

      Effect of blood vessel diameter on relative blood flow estimate in Doppler optical coherence tomography algorithms

      In vivo measurement of blood flow in the retina has been made possible with the advent of Fourier domain optical coherence tomography (OCT). Doppler OCT has seen many advances in recent years in algorithms used for quantifying blood flow. We compare the relative retinal blood flow estimates as measured by the standard phase-resolved (PR) algorithm and the more recent moving-scatterer-sensitive (MSS) algorithm as a function of vessel size. We find that the PR-to-MSS flow ratio significantly decreases with decreasing vessel diameter. We also develop a simulation to approximate the scattering from blood cells in tissue and compare the relative blood ...

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    4. Retinal blood flow measurement with ultrahigh-speed swept-source / Fourier domain optical coherence tomography

      Retinal blood flow measurement with ultrahigh-speed swept-source / Fourier domain optical coherence tomography

      Doppler OCT is a functional extension of OCT that provides information on flow in biological tissues. We present a novel approach for total retinal blood flow assessment using ultrahigh speed Doppler OCT. A swept source / Fourier domain OCT system at 1050 nm was used for 3D imaging of the human retina. The high axial scan rate of 200 kHz allowed measuring the high flow velocities in the central retinal vessels. By analyzing en-face images extracted from 3D Doppler data sets, absolute flow for single vessels as well as total retinal blood flow can be measured using a simple and robust ...

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    5. Corneal power measurement with Fourier-domain optical coherence tomography

      Corneal power measurement with Fourier-domain optical coherence tomography
      Setting Doheny Eye Institute, Los Angeles, California, USA. Design Cross-sectional study. Methods A Fourier-domain OCT system (RTVue) was used to scan normal eyes, eyes after myopic laser in situ keratomileusis (LASIK), and keratoconic eyes. After the corneal surfaces were delineated, the system calculated anterior and posterior corneal powers by curve fitting over the central 3.0 mm diameter area. Net corneal power was calculated using a thick-lens formula. The repeatability of the calculations was evaluated by the pooled standard deviation of 3 measurements from the same visit. The net corneal power values were compared with standard automated keratometry measurements (IOLMaster ...
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    6. Pilot Study of Optical Coherence Tomography Measurement of Retinal Blood Flow in Retinal and Optic Nerve Diseases

      Pilot Study of Optical Coherence Tomography Measurement of Retinal Blood Flow in Retinal and Optic Nerve Diseases
      Purpose: To investigate blood flow changes in retinal and optic nerve diseases with Doppler Fourier domain optical coherence tomography (OCT). Methods: Sixty-two participants were divided into five groups: normal, glaucoma, nonarteritic ischemic optic neuropathy (NAION), treated proliferative diabetic retinopathy (PDR), and branch retinal vein occlusion (BRVO). Doppler OCT was used to scan concentric circles of 3.4 and 3.75 mm diameters around the optic nerve head. Flow in retinal veins were calculated from the OCT velocity profiles. Arterial and venous diameters were measured from OCT Doppler and reflectance images. Results: Total retinal blood flow in normal subjects averaged 47 ...
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    7. Ultrahigh speed 1050nm swept source / Fourier domain OCT retinal and anterior segment imaging at 100,000 to 400,000 axial scans per second

      Ultrahigh speed 1050nm swept source / Fourier domain OCT retinal and anterior segment imaging at 100,000 to 400,000 axial scans per second
      We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000 - 400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, sensitivity, axial resolution, and imaging depth. Variable rate A/D optical clocking is used to acquire linear-in-k OCT fringe data at 100kHz axial scan rate with 5.3um axial resolution in tissue. Fixed rate sampling at 1 GSPS achieves a 7.5mm imaging range in tissue with 6.0um axial resolution at 100kHz axial scan rate. A 200kHz axial scan rate with 5.3um axial resolution over ...
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    8. Method of eye examination by optical coherence tomography

      Method of eye examination by optical coherence tomography
      A method of performing an OCT image scan is presented. Other images are taken and a template is formed to correct the OCT images, for example, for eye motion, blood vessel placement, and center offset. In some embodiments, video images are taken simultaneously with the OCT images and utilized to correct the OCT images. In some embodiments, a template OCT image is formed prior to acquisition of the OCT images and the template OCT image is utilized as a template from which to correct all of the OCT images.
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    9. Measurement of central corneal thickness by high-resolution Scheimpflug imaging, Fourier-domain optical coherence tomography and ultrasound pachymetry

      Measurement of central corneal thickness by high-resolution Scheimpflug imaging, Fourier-domain optical coherence tomography and ultrasound pachymetry
      Purpose: To compare the repeatability and reproducibility of central corneal thickness (CCT) measurements by high-resolution (HR) rotating Scheimpflug imaging and Fourier-domain optical coherence tomography (FD-OCT). CCT measurements were compared to those determined by ultrasound pachymetry (UP).Methods: In 35 healthy eyes, intra-observer repeatability for HR Scheimpflug (Pentacam) and FD-OCT (RTVue) systems was determined in consecutive images taken by an observer in the shortest time possible. Imaging was repeated again by a second observer to evaluate inter-observer reproducibility. The CCT measurements were compared among Scheimpflug, FD-OCT and UP images.Results: Mean coefficients of repeatability were 0.48% for Scheimpflug and 0 ...
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    10. Pachymetric mapping with Fourier-domain optical coherence tomography

      Pachymetric mapping with Fourier-domain optical coherence tomography

      Purpose To evaluate the repeatability of Fourier-domain optical coherence tomography (OCT) pachymetric mapping and compare central corneal thickness (CCT) measurements by OCT, ultrasound pachymetry, and scanning-slit tomography. Setting Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. Methods A Fourier-domain OCT system was used to map the corneal thickness in normal eyes with scans centered on the corneal vertex or the pupil. Repeatability of central and pericentral map sectors was assessed by pooled standard deviation. The CCT measurements were compared between the OCT, ultrasound, and scanning-slit devices. Results Pupil centration (SD: 1.3 μm central, 1.8 to ...

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    11. Statistics of Optical Coherence Tomography Data From Human Retina

      Statistics of Optical Coherence Tomography Data From Human Retina
      Optical coherence tomography (OCT) has recently become one of the primary methods for non-invasive probing of the human retina. The pseudo-image formed by OCT (the socalled B-scan) varies probabilistically across pixels due to complexities in the measurement technique. Hence, sensitive automatic procedures of diagnosis using OCT may exploit statistical analysis of the spatial distribution of reflectance. In this paper, we perform a statistical study of retinal OCT data. We find that the stretched-exponential probability density function can model well the distribution of intensities in OCT pseudo-images. Moreover, we show a small, but significant correlation between neighbor pixels when measuring OCT ...
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    12. Imaging the Eye from Front to Back with RTVue Fourier-Domain Optical Coherence Tomography (Book)

      Imaging the Eye from Front to Back with RTVue Fourier-Domain Optical Coherence Tomography (Book)

      Fourier-Domain optical coherence tomography (OCT) is the latest technology available to provide high-speed, high-resolution imaging of the cornea, anterior chamber angle, macula and optic nerve head. Imaging the Eye from Front to Back with RTVue Fourier-Domain Optical Coherence Tomography (WW 141 I31 2010) by first author Dr. David Huang of Doheny Eye Institute and Drs. Jay S. Duker, James G. Fujimoto, Bruno Lumbroso, Joel S. Schuman, and Robert N. Weinreb covers up-to-date OCT technology and diagnostic software of the RTVue. Topics covered include:

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    13. Reproducibility of Tear Meniscus Measurement by Fourier-Domain Optical Coherence Tomography: A Pilot Study

      BACKGROUND AND OBJECTIVE To study the reproducibility of tear meniscus measurement with high-speed high-resolution Fourier-domain optical coherence tomography (FD-OCT). PATIENTS AND METHODS Twenty normal participants were enrolled in this prospective study. The lower tear meniscus in the right eye of each subject was imaged by vertical scans centered on the inferior cornea and the lower eyelid using an FD-OCT system (RTVue; Optovue, Inc., Fremont, CA) with a corneal adaptor. The system performs 26,000 axial scans per second and has a 5-micron axial resolution. Each subject was examined at two visits 30 to 60 days apart. Each eye was scanned ...
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    14. Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography

      Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography
      Purpose: To map ganglion cell complex (GCC) thickness with high-speed Fourier-domain optical coherence tomography (FD-OCT) and compute novel macular parameters for glaucoma diagnosis.Design: Observational, cross-sectional study.Participants: One hundred seventy-eight participants in the Advanced Imaging for Glaucoma Study, divided into 3 groups: 65 persons in the normal group, 78 in the perimetric glaucoma group (PG), and 52 in the preperimetric glaucoma group (PPG).Methods: The RTVue FD-OCT system was used to map the macula over a 7×6 mm region. The macular OCT images were exported for automatic segmentation using software we developed. The program measured macular retinal (MR ...
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    15. High-resolution optical coherence tomography visualization of Lasik flap displacement

      Uneventful myopic laser in situ keratomileusis (LASIK) was performed in both eyes of a 33-year-old woman. Two weeks after LASIK, examination of the left eye revealed flap striae radiating inferonasally from the superior hinge. The flap was relifted and repositioned to remove the irregular astigmatism and reduce the striae. Before the flap was relifted, Fourier-domain optical coherence tomography (FD-OCT) showed the gap at the temporal flap, which had not been detected by biomicroscopy. After the flap was relifted, FD-OCT documented that the gap was closed. High-resolution FD-OCT was helpful in the visualization and management of flap displacement.
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    16. Ophthalmic Optical Coherence Tomography Market: Past, Present, & Future

      In 1992 the first commercial optical coherence tomography (OCT) company was started. It was called Advanced Ophthalmic Devices (AOD) and as the name implies was focused on the ophthalmology market. AOD grew out of research at the Massachusetts Institute of Technology, Massachusetts Eye and Ear Infir
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    17. Gaussian fitting on mean curvature maps of parameterization of corneal ectatic diseases

      The present invention discloses a method for characterizing ectatic diseases of the cornea by computing a mean curvature map of the anterior or posterior surfaces of the cornea and fitting the map to a Gaussian function to characterize the surface features of the map. Exemplary ectatic disease that may be characterized include keratoconus and pellucid marginal degeneration. Also disclosed are a system for diagnosing ectatic disease of the cornea and a computer readable medium encoding the method thereof.
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    18. Retinal blood flow detection in diabetic patients by Doppler Fourier domain optical coherence tomography

      Retinal blood flow detection in diabetic patients by Doppler Fourier domain optical coherence tomography

      We present human retinal blood flow investigation for diabetic patients using Doppler Fourier domain optical coherence tomography (FDOCT). The scanning pattern consisted of two concentric circles around the optic nerve head. The blood flow in one patient with diabetes and no retinpathy and another ... [Opt. Express 17, 4061-4073 (2009)]

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    19. Investigation of retinal blood flow in normal and glaucoma subjects by doppler fourier-domain optical coherence tomography

      We present in vivo human retinal blood flow investigation using Fourier domain optical coherence tomography. A pilot study was performed to evaluate the total retinal blood flow in glaucoma patients and normal subjects. For normal people, the measured total retinal flow was between 40.8 and 52.9 [mu ... [Proc. SPIE 7168, 71680B (2009)] published Thu Feb 19, 2009.

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    20. Measurement of total blood flow in the normal human retina using Doppler Fourier-domain optical coherence tomography

      Aim: To measure total retinal blood flow in normal human eyes using Doppler Fourier-domain optical coherence tomography (FD-OCT). Methods: 10 normal people aged 35 to 69 years were measured for the right eye using Doppler FD-OCT. Double circular scans around the optic nerve heads were used. Four pairs of circular scans that transected all retinal branch vessels were completed in 2 seconds. Total retinal blood flow was obtained by summing the flows in the branch veins. Measurements from the eight scans were averaged. Veins with diameters > 33 µm were taken into account. Results: Total retinal blood flow could be measured ...

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    21. Agreement Between Stratus and Visante Optical Coherence Tomography Systems in Tear Meniscus Measurements.

      Aim: To compare the tear meniscus height (TMH) measurements provided by the Stratus and Visante optical coherence tomography systems. Methods: A cross-section image of the lower tear meniscus was captured with both instruments in 26 volunteers. An external application was used to manually measure the TMH as imaged by the Stratus; measurements by the Visante were analyzed by the internal software. Only 1 eye for each subject was considered for statistical analysis. Results: The mean (±SD) TMH was higher when measured by the Visante (0.28 ± 0.12 mm) compared with the Stratus (0.23 ± 0.07 mm, P = 0 ...
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    22. Pattern Analysis Of Retinal Maps For Diagnosis Of Optic Nerve Diseases By Optical Coherence Tomography (Wo 2008/157406)

      Pattern Analysis Of Retinal Maps For Diagnosis Of Optic Nerve Diseases By Optical Coherence Tomography (Wo 2008/157406)
      Methods for analyzing retinal tomography maps to detect patterns of optic nerve diseases such as glaucoma, optic neuritis, anterior ischemic optic neuropathy are disclosed in this invention. The areas of mapping include the macula centered on the fovea, and the region centered on the optic nerve head. The retinal layers that are analyzed include the nerve fiber, ganglion cell, inner plexiform and inner nuclear layers and their combinations. The overall retinal thickness can also be analyzed. Pattern analysis are applied to the maps to create single parameter for diagnosis and progression analysis of glaucoma and optic neuropathy.
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    23. Retinal blood flow measurement by circumpapillary Fourier domain Doppler optical coherence tomography

      We present in vivo human total retinal blood flow measurements using Doppler Fourier domain optical coherence tomography (OCT). The scan pattern consisted of two concentric circles around the optic nerve head, transecting all retinal branch arteries and veins. The relative positions of each blood vessel in the two OCT conic cross sections were measured and used to determine the angle between the OCT beam and the vessel. The measured angle and the Doppler shift profile were used to compute blood flow in the blood vessel. The flows in the branch veins was summed to give the total retinal blood flow ...

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    24. Keratoconus Diagnosis with Optical Coherence Tomography Pachymetry Mapping

      Objective To detect abnormal corneal thinning in keratoconus using pachymetry maps measured by high-speed anterior segment optical coherence tomography (OCT). Design Cross-sectional observational study. Participants Thirty-seven keratoconic eyes from 21 subjects and 36 eyes from 18 normal subjects. Methods The OCT system operated at a 1.3 μm wavelength with a scan rate of 2000 axial scans per second. A pachymetry scan pattern (8 radials, 128 axial scans each; 10 mm diameter) centered at the corneal vertex was used to map the corneal thickness. The pachymetry map was divided into zones by octants and annular rings. Five pachymetric parameters were ...
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    193-216 of 237 « 1 2 3 4 5 6 7 8 9 10 »
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    1. (237 articles) David Huang
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