1. Articles from Ou Tan

    1-24 of 61 1 2 3 »
    1. Prospective evaluation of optical coherence tomography for disease detection in the Casey mobile eye clinic

      Prospective evaluation of optical coherence tomography for disease detection in the Casey mobile eye clinic

      This study was designed to evaluate iVue Spectral-domain optical coherence tomography (SD-OCT) effectiveness in screening for eye disease compared to clinical examination. Subjects were recruited from the Casey Eye Community Outreach Program Mobile Clinic during its routinely scheduled outreach clinics to indigent, underserved populations throughout Oregon. Macular optical coherence tomography interpretation and automated optical coherence tomography analysis were compared to the clinical examination, with specific attention to findings indicative of retinal abnormalities, risks for glaucoma, and narrow angles. As a result, a total of 114 subjects were included in this study. In diabetics, optical coherence tomography and clinical exam were ...

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    2. Optical coherence tomographic angiography study of perfusion recovery after surgical lowering of intraocular pressure

      Optical coherence tomographic angiography study of perfusion recovery after surgical lowering of intraocular pressure

      We investigated the time and location of retinal perfusion recovery after surgical intraocular pressure (IOP) lowering in glaucoma by using optical coherent tomography angiography (OCTA). Seventeen patients were analyzed. The 4.5 × 4.5-mm OCTA scans centered on the disc were performed preoperatively and postoperatively at 6 weeks, 3 months, and 6 months. The peripapillary retinal nerve fiber layer (NFL) thickness, NFL plexus capillary density (NFLP-CD) and visual field (VF) were measured overall and in 8 corresponding sectors. The low-perfusion area (LPA) was used to assess the cumulative area where local NFLP-CD was significantly below normal. At 6 months, the ...

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    3. Effect of algorithms and covariates in glaucoma diagnosis with optical coherence tomography angiography

      Effect of algorithms and covariates in glaucoma diagnosis with optical coherence tomography angiography

      Purpose: To assess the effects of algorithms and covariates in glaucoma diagnosis with optical coherence tomography angiography (OCTA). Methods: In this prospective cross-sectional study, one eye each of 36 normal controls and 64 patients with glaucoma underwent 4.5 mm disc-centred and 6 mm macula-centred OCTA scans. The peripapillary nerve fibre layer plexus capillary density (NFLP-CD) and macular superficial vascular complex vessel density (SVC-VD) were measured using both a commercial algorithm (AngioAnalytics) and a custom algorithm (Center for Ophthalmic Optics & Lasers Angiography Reading Toolkit (COOL-ART)). The nerve fibre layer and ganglion cell complex thicknesses were measured on structural OCT. Results ...

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    4. Postdoctoral Research Fellowship position in the Center for Ophthalmic Optics and Lasers, Casey Eye Institute, Oregon Health & Science University

      Postdoctoral Research Fellowship position  in the Center for Ophthalmic Optics and Lasers, Casey Eye Institute, Oregon Health & Science University

      A postdoctoral research fellowship position is immediately available in the Center for Ophthalmic Optics and Lasers www.COOLLab.net , Casey Eye Institute, Oregon Health & Science University. The fellowship will focus on interdisciplinary project in the field of optical imaging, image analysis, and glaucoma diagnosis. Ph.D. in Biomedical Engineering, Electrical Engineering, Computing Science, Optics, or a related field is required. Demonstrated excellence in one or more of the following areas is preferred: expertise in optical coherence tomography, image processing, artificial intelligence and machine learning, statistical analysis, C++/Matlab/R programming for data analysis. Please Contact Dr. Ou Tan ( tano@ohsu ...

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    5. Split-spectrum amplitude-decorrelation angiography with optical coherence tomography

      Split-spectrum amplitude-decorrelation angiography with optical coherence tomography

      Amplitude decorrelation measurement is sensitive to transverse flow and immune to phase noise in comparison to Doppler and other phase-based approaches. However, the high axial resolution of OCT makes it very sensitive to the pulsatile bulk motion noise in the axial direction. To overcome this limitation, we developed split-spectrum amplitude-decorrelation angiography (SSADA) to improve the signal-to-noise ratio (SNR) of flow detection. The full OCT spectrum was split into several narrower bands. Inter-B-scan decorrelation was computed using the spectral bands separately and then averaged. The SSADA algorithm was tested on in vivo images of the human macula and optic nerve head ...

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    6. Estimating Visual Field Mean Deviation using Optical Coherence Tomographic Nerve Fiber Layer Measurements in Glaucoma Patients

      Estimating Visual Field Mean Deviation using Optical Coherence Tomographic Nerve Fiber Layer Measurements in Glaucoma Patients

      To construct an optical coherence tomography (OCT) nerve fiber layer (NFL) parameter that has maximal correlation and agreement with visual field (VF) mean deviation (MD). The NFL_MD parameter in dB scale was calculated from the peripapillary NFL thickness profile nonlinear transformation and VF area-weighted averaging. From the Advanced Imaging for Glaucoma study, 245 normal, 420 pre-perimetric glaucoma (PPG), and 289 perimetric glaucoma (PG) eyes were selected. NFL_MD had significantly higher correlation (Pearson R: 0.68 vs 0.55, p < 0.001) with VF_MD than the overall NFL thickness. NFL_MD also had significantly higher sensitivity in detecting PPG (0.14 vs ...

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    7. Sectorwise Visual Field Simulation Using Optical Coherence Tomographic Angiography Nerve Fiber Layer Plexus Measurements in Glaucoma

      Sectorwise Visual Field Simulation Using Optical Coherence Tomographic Angiography Nerve Fiber Layer Plexus Measurements in Glaucoma

      Purpose To simulate 24-2 visual field (VF) using optical coherence tomographic angiography (OCTA) for glaucoma evaluation. Design Cross-sectional study. Methods One eye each of 39 glaucoma and 31 age-matched normal participants was scanned using 4.5-mm OCTA scans centered on the disc. The peripapillary retinal nerve fiber layer plexus capillary density (NFLP_CD, %area) was measured. The NFLP_CD and 24-2 VF maps were divided into 8 corresponding sectors using an extension of Garway-Heath scheme. Results Sector NFLP_CD was transformed to a logarithmic dB scale and converted to sector simulated VF deviation maps. Comparing simulated and actual 24-2 VF maps, the worst ...

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    8. Systems and methods of glaucoma diagnosis based on frequency analysis of inner retinal surface profile measured by optical coherence tomography

      Systems and methods of glaucoma diagnosis based on frequency analysis of inner retinal surface profile measured by optical coherence tomography

      A method for detecting glaucoma in a subject based on spatial frequency analysis of the inner limiting membrane (ILM) as obtained from optical coherence tomography (OCT) image data is disclosed. Based on the spatial frequency content of the analyzed ILM profile, a quantity called the Retinal surface contour variability (RSCV) is calculated and the presence or absence of a glaucoma condition is determined based on the RSCV magnitude.

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    9. Nerve Fiber Flux Analysis Using Wide-Field Swept-Source Optical Coherence Tomography

      Nerve Fiber Flux Analysis Using Wide-Field Swept-Source Optical Coherence Tomography

      Purpose : To devise a method to quantify nerve fibers over their arcuate courses over an extended peripapillary area using optical coherence tomography (OCT). Methods : Participants were imaged with 8 × 8-mm volumetric OCT scans centered at the optic disc. A new quantity, nerve fiber flux (NFF), represents the cross-sectional area transected perpendicular to the nerve fibers. The peripapillary area was divided into 64 tracks with equal flux. An iterative algorithm traced the trajectory of the tracks assuming that the relative distribution of the NFF was conserved with compensation for fiber connections to ganglion cells on the macular side. Average trajectory was ...

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    10. Assessment Of Retinal Blood Flow In Diabetic Retinopathy Using Doppler FOURIER-DOMAIN Optical Coherence Tomography

      Assessment Of Retinal Blood Flow In Diabetic Retinopathy Using Doppler FOURIER-DOMAIN Optical Coherence Tomography

      Purpose: To evaluate retinal blood flow measurements in normal eyes and eyes with varying levels of diabetic retinopathy (DR) using Doppler Fourier-domain optical coherence tomography (FD-OCT). Methods: Twenty-two eyes of 19 subjects, 10 with severe nonproliferative DR (NPDR) and 12 with proliferative DR (PDR), were compared with 44 eyes of 40 healthy control subjects. All eyes were scanned by RTvue FD-OCT. Color disk photographs and cube/volume scans of the optic nerve head were obtained. Doppler OCT scans and accessory imaging data were imported into Doppler OCT of Retinal Circulation grading software to calculate TRBF and vascular parameters (e.g ...

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    11. Comparison of Glaucoma Progression Detection by Optical Coherence Tomography and Visual Field

      Comparison of Glaucoma Progression Detection by Optical Coherence Tomography and Visual Field

      Purpose To compare longitudinal glaucoma progression detection using optical coherence tomography (OCT) and visual field (VF). Design Validity assessment Method We analyzed subjects with more than 5 follow-up visits (every 6 months) in the multi-center Advanced Imaging for Glaucoma Study. Fourier-domain optical coherence tomography (OCT) was used to map the thickness of the peripapillary retinal nerve fiber layer (NFL) and ganglion cell complex (GCC). OCT-based progression detection was defined as a significant negative trend for either NFL or GCC. VF progression was reached if either the event or trend analysis reached significance. Result The analysis included 417 glaucoma suspect/pre-perimetric ...

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    12. Optical coherence tomography angiography enhances the detection of optic nerve damage in multiple sclerosis

      Optical coherence tomography angiography enhances the detection of optic nerve damage in multiple sclerosis

      Background Quantitative assessment of optic nerve damage is important in the evaluation of optic neuritis (ON) and multiple sclerosis (MS). Objective To detect optic nerve damage using optical coherence tomography (OCT) and OCT angiography in MS. Methods Peripapillary retinal nerve fibre layer (NFL) thickness, macular ganglion cell complex (GCC) thickness and Optic Nerve Head Flow Index (ONH-FI) were measured. The ONH-FI was defined as flow signal averaged over the optic disc. Diagnostic accuracy was evaluated by the area under the receiver-operating characteristics curve (AROC). Results Sixty-eight eyes of 45 MS participants and 55 eyes of 32 healthy controls (HCs) were ...

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    13. Handheld OCT Angiography and Ultra–Wide-Field OCT in Retinopathy of Prematurity

      Handheld OCT Angiography and Ultra–Wide-Field OCT in Retinopathy of Prematurity

      Importance Retinopathy of prematurity (ROP) is a leading cause of childhood blindness worldwide. Optical coherence tomography (OCT) has improved the care of adults with vitreoretinal disease, and OCT angiography (OCTA) is demonstrating promise as a technique to visualize the retinal vasculature with lower risk and cost than fluorescein angiography. However, to date, there are no commercially available devices able to obtain ultra–wide-field OCT or OCTA images in neonates. Objective To obtain ultra–wide-field OCT and OCTA images in neonates with ROP using a prototype handheld OCT and OCTA device. Design, Setting, and Participants This observational case series was conducted ...

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    14. Methods and systems to measure corneal epithelial thickness and power, stromal thickness, subepithelial corneal power and topography for disease diagnosis

      Methods and systems to measure corneal epithelial thickness and power, stromal thickness, subepithelial corneal power and topography for disease diagnosis

      This invention discloses methods and systems for measuring corneal epithelial thickness and power, stromal thickness, subepitheila corneal power and topography. The systems and methods disclosed herein are non-invasive, non-contact and automated imaging methods which preferably makes use of Fourier-domain optical tomography. Also disclosed herein are scanning patterns and image analysis methods for utilizing and analyzing Fourier-domain optical coherence tomography images to obtain information about conical epithelial and stromal properties as well as parameters useful for evaluating the properties. The methods and systems described herein are useful as eye disease diagnostic tools and eye surgery planning tools.

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    15. Retinal Blood Flow Response to Hyperoxia Measured With En Face Doppler Optical Coherence Tomography

      Retinal Blood Flow Response to Hyperoxia Measured With En Face Doppler Optical Coherence Tomography

      Purpose : To use multiplane en face Doppler optical coherence tomography (OCT) to measure the change in total retinal blood flow (TRBF) in response to hyperoxia. Methods : One eye of each healthy human participant ( n = 8) was scanned with a commercial high-speed (70-kHz) spectral OCT system. Three repeated scans were captured at baseline and after 10 minutes of oxygen (hyperoxia) by open nasal mask. The procedure was performed twice on day 1 and once more on day 2. Blood flow of each vein was estimated using Doppler OCT at an optimized en face plane. The TRBF was summed from all veins ...

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    16. Glaucoma Increases Retinal Surface Contour Variability as Measured by Optical Coherence Tomography

      Glaucoma Increases Retinal Surface Contour Variability as Measured by Optical Coherence Tomography

      Purpose : We investigated the feasibility of glaucoma detection by measuring retinal surface contour variability (RSCV) using optical coherence tomography (OCT). Methods : The peripapillary region in one eye of each participant was scanned over an 8 × 8 mm area with a swept source OCT prototype. The retinal surface contour was sampled at approximately 1.5- to 3.5-mm radius circles centered on the optic nerve head. The RSCV is defined as the average log value within a middle spatial frequency band of the Fourier transform to the elevation profile of the inner retinal surface. The spatial frequency band was optimized to ...

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    17. Subclinical keratoconus detection by pattern analysis of corneal and epithelial thickness maps with optical coherence tomography

      Subclinical keratoconus detection by pattern analysis of corneal and epithelial thickness maps with optical coherence tomography

      Purpose To screen for subclinical keratoconus by analyzing corneal, epithelial, and stromal thickness map patterns with Fourier-domain optical coherence tomography (OCT). Setting Four centers in the United States. Design Cross-sectional observational study. Methods Eyes of normal subjects, subclinical keratoconus eyes, and the topographically normal eye of a unilateral keratoconus patient were studied. Corneas were scanned using a 26 000 Hz Fourier-domain OCT system (RTVue). Normal subjects were divided into training and evaluation groups. Corneal, epithelial, and stromal thickness maps and derived diagnostic indices, including pattern standard deviation (PSD) variables and pachymetric map–based keratoconus risk scores, were calculated from the ...

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    18. Longitudinal and Cross-Sectional Analyses of Age and Intraocular Pressure Effects on Retinal Nerve Fiber Layer and Ganglion Cell Complex Thickness

      Longitudinal and Cross-Sectional Analyses of Age and Intraocular Pressure Effects on Retinal Nerve Fiber Layer and Ganglion Cell Complex Thickness

      Purpose : To study the effect of age and intraocular pressure (IOP) on retinal nerve fiber layer (NFL) and ganglion cell complex (GCC) thickness in normal eyes. Methods : We analyzed the data from subjects enrolled in the multi-center longitudinal Advanced Imaging for Glaucoma (AIG) Study (www.AIGStudy.net). The data included yearly visits from the normal subjects group in the AIGS study. Fourier-domain optical coherence tomography (OCT) was used to map the thickness of NFL and GCC three times on each visit. To adjust for the repeated measurements for the same subjects, mixed effect models were used to evaluate the longitudinal ...

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    19. Regression Analysis of Optical Coherence Tomography Disc Variables for Glaucoma Diagnosis

      Regression Analysis of Optical Coherence Tomography Disc Variables for Glaucoma Diagnosis

      Purpose: To report diagnostic accuracy of optical coherence tomography (OCT) disc variables using both time-domain (TD) and Fourier-domain (FD) OCT, and to improve the use of OCT disc variable measurements for glaucoma diagnosis through regression analyses that adjust for optic disc size and axial length-based magnification error. Design: Observational, cross-sectional. Participants: In total, 180 normal eyes of 112 participants and 180 eyes of 138 participants with perimetric glaucoma from the Advanced Imaging for Glaucoma Study. Methods: Diagnostic variables evaluated from TD-OCT and FD-OCT were: disc area, rim area, rim volume, optic nerve head volume, vertical cup-to-disc ratio (CDR), and horizontal ...

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    20. Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography

      Predicting Development of Glaucomatous Visual Field Conversion Using Baseline Fourier-Domain Optical Coherence Tomography

      Purpose To predict the development of glaucomatous visual field (VF) defects using Fourier-domain optical coherence tomography (FD-OCT) measurements at baseline visit. Design Multi-center longitudinal observational study. Glaucoma suspects and pre-perimetric glaucoma participants in the Advanced Imaging for Glaucoma Study. Methods The optic disc, the peripapillary retinal nerve fiber layer (NFL), and macular ganglion cell complex (GCC) were imaged with FD-OCT VF was assessed every 6 months. Conversion to perimetric glaucoma was defined by VF pattern standard deviation (PSD) or glaucoma hemifield test (GHT) outside normal limits on 3 consecutive tests. Hazard ratios were calculated with the Cox proportional hazard model ...

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    21. Effect of Signal Intensity on Measurement of Ganglion Cell Complex and Retinal Nerve Fiber Layer Scans in Fourier-Domain Optical Coherence Tomography

      Effect of Signal Intensity on Measurement of Ganglion Cell Complex and Retinal Nerve Fiber Layer Scans in Fourier-Domain Optical Coherence Tomography

      Purpose : We determined the effect of Fourier-domain optical coherence tomography (OCT) signal strength index (SSI) and cropping on retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC) scan repeatability and measurement thickness. Methods : Eyes were enrolled in the longitudinal Advanced Imaging for Glaucoma Study. At each visit, three repeat scans from the optic nerve head and macular protocols were obtained. Each measurement was associated with an SSI value from 0 to 100. Measurements with similar SSI scores were grouped to calculate repeatability defined as pooled standard deviation. Within-visit analysis was used to determine how measured thickness changed in ...

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    22. Optical Coherence Tomography Glaucoma Detection Based On Retinal Vessel Relief Height

      Optical Coherence Tomography Glaucoma Detection Based On Retinal Vessel Relief Height

      Systems and techniques for detecting glaucoma in a subject based on retinal vessel relief height obtained from optical coherence tomography (OCT) image data are disclosed. In one example approach, a retinal vessel relief height relative to a retinal plane may be calculated from OCT image data and the presence or absence of a glaucoma condition may be determined based on the retinal vessel relief height.

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    23. En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

      En face Doppler total retinal blood flow measurement with 70 kHz spectral optical coherence tomography

      An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans ( 2 × 2     mm ) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The ...

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    24. Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography

      Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography

      We propose methods to align interferograms affected by trigger jitter to a reference interferogram based on the information (amplitude/phase) at a fixed-pattern noise location to reduce residual fixed-pattern noise and improve the phase stability of swept source optical coherence tomography (SS-OCT) systems. One proposed method achieved this by introducing a wavenumber shift (k-shift) in the interferograms of interest and searching for the k-shift that minimized the fixed-pattern noise amplitude. The other method calculated the relative k-shift using the phase information at the residual fixed-pattern noise location. Repeating this wavenumber alignment procedure for all A-lines of interest produced fixed-pattern noise ...

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