1. Articles from Ou Tan

    1-24 of 54 1 2 3 »
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. 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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    15. 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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    16. 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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    17. 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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    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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    23. 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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    24. 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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    1. (54 articles) David Huang
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