1. Articles from Ou Tan

    25-48 of 61 « 1 2 3 »
    1. Combining measurements from three anatomical areas for glaucoma diagnosis using Fourier-domain optical coherence tomography

      Combining measurements from three anatomical areas for glaucoma diagnosis using Fourier-domain optical coherence tomography

      Aims To improve the diagnostic power for glaucoma by combining measurements of peripapillary nerve fibre layer (NFL), macular ganglion cell complex (GCC) and disc variables obtained with Fourier-domain optical coherence tomography (FD-OCT) into the glaucoma structural diagnostic index (GSDI). Methods In this observational, cross-sectional study of subjects from the Advanced Imaging of Glaucoma Study, GCC and NFL of healthy and perimetrical glaucoma subjects from four major academic referral centres of the Advanced Imaging of Glaucoma Study were mapped with the RTVue FD-OCT. Global loss volume and focal loss volume parameters were defined using NFL and GCC normative reference maps. Optimal ...

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    2. Measurement of retinal blood flow in normal Chinese American subjects by Doppler Fourier-domain optical coherence tomography

      Measurement of retinal blood flow in normal Chinese American subjects by Doppler Fourier-domain optical coherence tomography

      PURPOSE: To measure total retinal blood flow (TRBF) in normal, healthy Chinese-Americans using semi-automated analysis of Doppler Fourier-domain optical coherence tomography (FD-OCT) scans. METHODS: Two hundred sixty-six normal, healthy Chinese-American participants (266 eyes) were enrolled from The Chinese American Eye Study (CHES). All participants underwent complete ophthalmic examination, including best-corrected visual acuity, indirect ophthalmoscopy and Doppler FD-OCT imaging, using the circumpapillary double circular scan protocol. TRBF and other vascular parameters (e.g. venous and arterial cross-sectional area and their velocities) were calculated using Doppler OCT of Retinal Circulation software. Associations between TRBF and other clinical parameters were assessed using bivariate ...

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    3. Variability and Repeatability of Quantitative, Fourier Domain-OCT Doppler Blood Flow in Young and Elderly Healthy Subjects

      Variability and Repeatability of Quantitative, Fourier Domain-OCT Doppler Blood Flow in Young and Elderly Healthy Subjects

      The purpose of this study was to determine the within-session variability and between-session repeatability of spectral Fourier-domain optical coherence tomography (Doppler FD-OCT) Doppler retinal blood flow measurements in young, and elderly subjects. Methods: Doppler FD-OCT blood flow was measured using the RTVue system (Optovue Inc., USA). One eye of each of 20 healthy young (24.7 ± 2.7 years) and 16 healthy elderly (64.6 ± 5.1 years) subjects was randomly selected and the pupil was dilated. The double circular scanning pattern of the RTVue was employed. Six Doppler FD-OCT measurements (i.e. each separate measurement comprising an upper, and ...

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    4. Dual-Angle Protocol for Doppler Optical Coherence Tomography to Improve Retinal Blood Flow Measurement

      Dual-Angle Protocol for Doppler Optical Coherence Tomography to Improve Retinal Blood Flow Measurement

      Purpose: To compare the performance of two different multiple-scan protocols for total retinal blood flow (TRBF) measurement using Doppler optical coherence tomography (OCT). Methods: In the “single-angle” protocol, five Doppler scans were acquired at a single beam angle. In the “dual-angle” protocol, three scans were obtained with the OCT beam passing through the supranasal portion of the pupil and three through the infranasal portion. The data were analyzed using a custom software termed “Doppler OCT of Retinal Circulation” (DOCTORC) to generate TRBF measurements. In DOCTORC, the measurement of a vein was considered unreliable if the Doppler angle was less than ...

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    5. Assessment of total retinal blood flow using Doppler Fourier Domain Optical Coherence Tomography during systemic hypercapnia and hypocapnia

      Assessment of total retinal blood flow using Doppler Fourier Domain Optical Coherence Tomography during systemic hypercapnia and hypocapnia

      The purpose of this study was to investigate changes in total retinal blood flow (RBF) using Doppler Fourier Domain Optical Coherence Tomography (Doppler FD‐OCT) in response to the manipulation of systemic partial pressure of CO 2 (P ET CO 2 ). Double circular Doppler blood flow scans were captured in nine healthy individuals (mean age ± standard deviation: 27.1 ± 4.1, six males) using the RTVue ™ FD‐OCT (Optovue). P ET CO 2 was manipulated using a custom‐designed computer‐controlled gas blender (RespirAct ™ ) connected to a sequential gas delivery rebreathing circuit. Doppler FD‐OCT measurements were captured at baseline ...

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    6. Grader learning effect and reproducibility of Doppler Spectral‐Domain Optical Coherence Tomography derived retinal blood flow measurements

      Grader learning effect and reproducibility of Doppler Spectral‐Domain Optical Coherence Tomography derived retinal blood flow measurements

      Purpose To investigate grader learning effect and to quantify intergrader reproducibility of Doppler Spectral-Domain Optical Coherence Tomography (SD-OCT) derived retinal blood flow measurements. Methods Fifteen healthy young subjects (mean age 28.44; SD 3 years) underwent Doppler SD-OCT scans of one eye using the circumpapillary double circular scan protocol of the Optovue RTVue by one of two experienced operators. One trained (i.e. having undergone certification) and one novice (i.e. preliminary training comprising five standard practice data sets) individual then graded a standardized set of scans, consisting of 15 data sets (session 1) using custom Doppler Optical Coherence Tomography ...

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    7. Quantitative Optical Coherence Tomography Angiography of Choroidal Neovascularization in Age-related Macular Degeneration

      Quantitative Optical Coherence Tomography Angiography of Choroidal Neovascularization in Age-related Macular Degeneration

      Purpose To detect and quantify choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD) using optical coherence tomography (OCT) angiography. Design Observational, cross-sectional study. Participants A total of 5 normal subjects and 5 subjects with neovascular AMD were included. Methods A total of 5 eyes with neovascular AMD and 5 normal age-matched controls were scanned by a high-speed (100 000 A-scans/seconds) 1050-nm wavelength swept-source OCT. The macular angiography scan covered a 3×3-mm area and comprised 200×200×8 A-scans acquired in 3.5 seconds. Flow was detected using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Motion artifacts were ...

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    8. Quantification Of Local Circulation With Oct Angiography

      Quantification Of Local Circulation With Oct Angiography

      Impaired intraocular blood flow within vascular beds in the human eye are associated with certain ocular diseases including, for example, glaucoma, diabetic retinopathy and age-related macular degeneration. A reliable method to quantify blood flow in one or more of the various intraocular vascular beds could provide insight into the vascular component of ocular disease pathophysiology.

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    9. Parafoveal Retinal Vascular Response to Pattern Visual Stimulation Assessed with OCT Angiography

      Parafoveal Retinal Vascular Response to Pattern Visual Stimulation Assessed with OCT Angiography

      We used optical coherence tomography (OCT) angiography with a high-speed swept-source OCT system to investigate retinal blood flow changes induced by visual stimulation with a reversing checkerboard pattern. The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to quantify blood flow as measured with parafoveal flow index (PFI), which is proportional to the density of blood vessels and the velocity of blood flow in the parafoveal region of the macula. PFI measurements were taken in 15 second intervals during a 4 minute period consisting of 1 minute of baseline, 2 minutes with an 8 Hz reversing checkerboard pattern stimulation, and 1 ...

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    10. Pilot Study of Doppler optical coherence tomography of retinal blood flow following laser photocoagulation in poorly controlled diabetic patients

      Pilot Study of Doppler optical coherence tomography of retinal blood flow following laser photocoagulation in poorly controlled diabetic patients

      Purpose: To investigate the effect of panretinal photocoagulation (PRP) on retinal blood flow and shear rate using Doppler Fourier-domain optical coherence tomography (FD-OCT) in poorly controlled diabetics with proliferative diabetic retinopathy (PDR). Methods: Prospective interventional pilot study in patients with a new clinical diagnosis of PDR. Retinal blood flow and vessel diameter was measured using Doppler FD-OCT according to a previously described method, immediately before PRP treatment and 7-8 weeks after the last PRP session. Results:10 patients with poorly controlled PDR (mean hemoglobin A1c= 9.2 +/-2.0%) and 10 control subjects were included in the study. PDR patients ...

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    11. Pattern analysis of retinal maps for the diagnosis of optic nerve diseases by optical coherence tomography

      Pattern analysis of retinal maps for the diagnosis of optic nerve diseases by optical coherence tomography

      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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    12. Assessment of Frame-Averaging Algorithms in OCT Image Analysis

      Assessment of Frame-Averaging Algorithms in OCT Image Analysis

      BACKGROUND AND OBJECTIVE: To evaluate frame registration and averaging algorithms for optical coherence tomography. PATIENTS AND METHODS: Twenty normal and 20 glaucomatous eyes were imaged. Objective differences were measured by comparing noise variance, spread of edge, and contrast-to-noise ratio. Subjective image quality was also evaluated. RESULTS: Two frame-averaging algorithms (FA400 and FA407) had better noise variance and contrast-to-noise ratio but worse spread of edge than did single frames ( P < .01). Both algorithms provided better subjective assessments of structure boundaries than did single images ( P < .001). FA407 had significantly lower spread of edge and better internal limiting membrane visualization than FA400 ...

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    13. Quantitative OCT angiography of optic nerve head blood flow

      Quantitative OCT angiography of optic nerve head blood flow

      Optic nerve head (ONH) blood flow may be associated with glaucoma development. A reliable method to quantify ONH blood flow could provide insight into the vascular component of glaucoma pathophysiology. Using ultrahigh-speed optical coherence tomography (OCT), we developed a new 3D angiography algorithm called split-spectrum amplitude-decorrelation angiography (SSADA) for imaging ONH microcirculation. In this study, a method to quantify SSADA results was developed and used to detect ONH perfusion changes in early glaucoma. En face maximum projection was used to obtain 2D disc angiograms, from which the average decorrelation values (flow index) and the percentage area occupied by vessels (vessel ...

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    14. Corneal Epithelial Thickness Mapping by Fourier-Domain Optical Coherence Tomography in Normal and Keratoconic Eyes

      Corneal Epithelial Thickness Mapping by Fourier-Domain Optical Coherence Tomography in Normal and Keratoconic Eyes

      Objective To map the corneal epithelial thickness with Fourier-domain optical coherence tomography (OCT) and to develop epithelial thickness–based variables for keratoconus detection. Design Cross-sectional observational study. Participants One hundred forty-five eyes from 76 normal subjects and 35 keratoconic eyes from 22 patients. Methods A 26 000-Hz Fourier-domain OCT system with 5-μm axial resolution was used. The cornea was imaged with a Pachymetry+Cpwr scan pattern (6-mm scan diameter, 8 radials, 1024 axial-scans each, repeated 5 times) centered on the pupil. Three scans were obtained at a single visit in a prospective study. A computer algorithm was developed to ...

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    15. Does optic nerve head size variation affect circumpapillary retinal nerve fiber layer thickness measurement by optical coherence tomography?

      Does optic nerve head size variation affect circumpapillary retinal nerve fiber layer thickness measurement by optical coherence tomography?

      Purpose: To determine the relationship between retinal nerve fiber layer (RNFL) thickness, optic disc size and image magnification. Methods: The cohort consisted of 196 normal eyes of 101 participants in the Advanced Imaging for Glaucoma Study (AIGS), a multi-center, prospective, longitudinal study to develop advanced imaging technologies for glaucoma diagnosis. Scanning laser tomography (HRT II) was used to measure disc size. Optical coherence tomography (Stratus) was used to perform circumpapillary RNFL thickness measurements using the standard fixed 3.46 mm nominal scan diameter. A theoretical model of magnification effects was developed to relate RNFL thickness (overall average) with axial length ...

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    16. Patterns of Ganglion Cell Complex and Nerve Fiber Layer Loss in Non-Arteritic Ischemic Optic Neuropathy by Fourier-Domain Optical Coherence Tomography

      Patterns of Ganglion Cell Complex and Nerve Fiber Layer Loss in Non-Arteritic Ischemic Optic Neuropathy by Fourier-Domain Optical Coherence Tomography

      Purpose: To characterize by Fourier-domain optical coherence tomography (FD-OCT) the loss of nerve fiber layer (NFL) and ganglion cell complex (GCC) in non-arteritic ischemic optic neuropathy (NAION). Methods: Patients diagnosed with NAION were enrolled and categorized into "superior field loss (SFL)," "inferior field loss (IFL)," and "bihemispheric field loss (BFL)" groups based on the Swedish interactive threshold algorithm 30-2 achromatic visual field (VF) tests. Six months after presentation, they were scanned by FD-OCT to map peripapillary NFL and macular GCC thicknesses. Age-matched normals were selected from participants in the Advanced Imaging for Glaucoma Study (www.AIGStudy.net). Deviation maps were ...

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    17. Relationship among visual field, blood flow, and neural structure measurements in glaucoma

      Relationship among visual field, blood flow, and neural structure measurements in glaucoma

      Purpose:To determine the relationship among visual field, neural structural, and blood flow measurements in glaucoma. Methods:Case-control study. Forty-seven eyes of 42 patients with perimetric glaucoma were age-matched with 27 normal eyes of 27 patients. All patients underwent Doppler Fourier-domain optical coherence tomography to measure retinal blood flow and standard glaucoma evaluation with visual field testing and quantitative structural imaging. Linear regression analysis was performed to analyze the relationship among visual field, blood flow, and structure, after all variables were converted to logarithmic decibel scale. Results:Retinal blood flow was reduced in glaucoma eyes compared to normal eyes (p

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    18. 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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    19. Speckle reduction in swept source optical coherence tomography images with slow-axis averaging

      Speckle reduction in swept source optical coherence tomography images with slow-axis averaging

      The effectiveness of speckle reduction using traditional frame averaging technique was limited in ultrahigh speed optical coherence tomography (OCT). As the motion between repeated frames was very small, the speckle pattern of the frames might be identical. This problem could be solved by averaging frames acquired at slightly different locations. The optimized scan range depended on the spot size of the laser beam, the smoothness of the boundary, and the homogeneity of the tissue. In this study we presented a method to average frames obtained within a narrow range along the slow-axis. A swept-source OCT with 100,000 Hz axial ...

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    20. Reproducibility of Retinal Blood Flow Measurements Derived From Semi-Automated Doppler OCT Analysis

      Reproducibility of Retinal Blood Flow Measurements Derived From Semi-Automated Doppler OCT Analysis
      BACKGROUND AND OBJECTIVE: To evaluate reproducibility and intergrader agreement of total retinal blood flow (TRBF) measurements obtained by semi-automated grading of Doppler Fourier-domain optical coherence tomography (FD-OCT) scans. PATIENTS AND METHODS: Doppler FD-OCT scans were obtained from 20 eyes of 18 subjects (10 glaucomatous, 10 normal). Scans were obtained using a circumpapillary scan protocol and analyzed using the Doppler OCT of Retinal Circulation software (version 2). Two masked, independent human graders manually refined the scans, adding or deleting vessels, changing vessel boundaries, and classifying vessels as veins or arteries. TRBF was calculated automatically by software summing flow in all veins ...
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    21. Mapping and diagnosis of macular edema by optical coherence tomography

      Mapping and diagnosis of macular edema by optical coherence tomography
      The present invention discloses a method for comparing the detection of clinically significant diabetic macular edema by an optical coherence tomography (OCT) grid scanning protocol and biomicroscopic examination. Also provided are computer implemented, automated systems for performing the method thereof and computer readable media encoding the method thereof.
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    22. Flicker-induced changes in retinal blood flow assessed by Doppler optical coherence tomography

      Flicker-induced changes in retinal blood flow assessed by Doppler optical coherence tomography

      We used Doppler Fourier-domain optical coherence tomography (OCT) to investigate flicker-induced changes of total retinal blood flow. Total retinal blood flow was measured by summing flows in veins imaged in double-circular scans around the optic disc. In 3 healthy volunteers, total retinal blood flow was measured before and 10-15 seconds after 30 seconds of flicker stimulation. The average blood flow increased 22.2% (p = 0.002). The total venous and arterial vessel cross-sectional area increased 11.3% (p < 0.001) and +2.7% (p = 0.28) respectively. The average venous and arterial flow velocity were calculated indirectly by dividing total retinal blood flow by total venous and arterial cross-sectional areas. They also increased by 8.8% (p = 0.046) and 18.3% (p = 0.004), respectively. These results show that human retinal blood flow increases after visible flicker stimulation, and this could be measured with OCT.

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    23. Methods for diagnosing glaucoma utilizing combinations of FD-OCT measurements from three anatomical regions of the eye

      Methods for diagnosing glaucoma utilizing combinations of FD-OCT measurements from three anatomical regions of the eye
      This invention discloses methods and systems for diagnosing glaucoma by combining diagnostic parameters derived from optical coherence tomography images of three different anatomic regions of the eye, including the macular ganglion cell complex (mGCC), the peripapillary nerve fiber layer (ppNFL), and the optic nerve head (ONH). The combined diagnostic parameters form a reduced set of global parameters, which are then fed to pre-trained machine classifiers as input to arrive at a single diagnostic indicator for glaucoma. Also disclosed are methods for training a machine classifier to be used in methods and systems of this invention.
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    24. 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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    Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography Statistics of Optical Coherence Tomography Data From Human Retina Split-spectrum amplitude-decorrelation angiography with optical coherence tomography Patterns of Ganglion Cell Complex and Nerve Fiber Layer Loss in Non-Arteritic Ischemic Optic Neuropathy by Fourier-Domain Optical Coherence Tomography Corneal Epithelial Thickness Mapping by Fourier-Domain Optical Coherence Tomography in Normal and Keratoconic Eyes Assessment of total retinal blood flow using Doppler Fourier Domain Optical Coherence Tomography during systemic hypercapnia and hypocapnia Quantification of biomechanical properties of human corneal scar using acoustic radiation force optical coherence elastography Longitudinal changes in complete avascular area assessed using anterior segmental optical coherence tomography angiography in filtering trabeculectomy bleb Quantitative Analysis of Radial Peripapillary Capillary Network in Patients With Papilledema Compared with Healthy Subjects Using Optical Coherence Tomography Angiography Reproducibility of Retinal Nerve Fiber Layer and Macular Thickness Measurements Using Spectral Domain Optical Coherence Tomography Analysis of Parainflammation in Chronic Glaucoma Using Vitreous-OCT Imaging Impact of Epiretinal Membrane on Optical Coherence Tomography Tools Used for Monitoring Glaucoma