1. Articles from Rohit Varma

    1-24 of 29 1 2 »
    1. Birefringent tissue-mimicking phantom for polarization-sensitive optical coherence tomography imaging

      Birefringent tissue-mimicking phantom for polarization-sensitive optical coherence tomography imaging

      Significance: Tissue birefringence is an important parameter to consider when designing realistic, tissue-mimicking phantoms. Options for suitable birefringent materials that can be used to accurately represent tissue scattering are limited. Aim: To introduce a method of fabricating birefringent tissue phantoms with a commonly used material-polydimethylsiloxane (PDMS)-for imaging with polarization-sensitive optical coherence tomography (PS-OCT). Approach: Stretch-induced birefringence was characterized in PDMS phantoms made with varying curing ratios, and the resulting phantom birefringence values were compared with those of biological tissues. Results: We showed that, with induced birefringence levels up to 2.1 × 10 - 4, PDMS can be used to resemble ...

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    2. Optimal number and orientation of anterior segment OCT images to measure ocular biometric parameters in angle closure eyes: the Chinese American Eye Study

      Optimal number and orientation of anterior segment OCT images to measure ocular biometric parameters in angle closure eyes: the Chinese American Eye Study

      Purpose: To assess the optimal number and orientation of anterior segment optical coherence tomography (AS-OCT) images for accurately measuring ocular biometric parameters in angle closure eyes. Methods: Subjects with angle closure, defined as >3 quadrants of non-visible pigmented trabecular meshwork on static gonioscopy, were selected from the Chinese American Eye Study. Mean angle opening distance (AOD500) was calculated using four images (0°-180°, 45°-225°, 90°-270° and 135°-315° meridians) from one eye per subject. Ten eyes from each quartile of AOD500 measurements were randomly selected for detailed 32-image analysis of 10 biometric parameters, including AOD500, iris curvature (IC ...

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    3. Generalisability and performance of an OCT-based deep learning classifier for community-based and hospital-based detection of gonioscopic angle closure

      Generalisability and performance of an OCT-based deep learning classifier for community-based and hospital-based detection of gonioscopic angle closure

      Purpose: To assess the generalisability and performance of a deep learning classifier for automated detection of gonioscopic angle closure in anterior segment optical coherence tomography (AS-OCT) images. Methods: A convolutional neural network (CNN) model developed using data from the Chinese American Eye Study (CHES) was used to detect gonioscopic angle closure in AS-OCT images with reference gonioscopy grades provided by trained ophthalmologists. Independent test data were derived from the population-based CHES, a community-based clinic in Singapore, and a hospital-based clinic at the University of Southern California (USC). Classifier performance was evaluated with receiver operating characteristic curve and area under the ...

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    4. Deep Neural Network for Scleral Spur Detection in Anterior Segment OCT Images: The Chinese American Eye Study

      Deep Neural Network for Scleral Spur Detection in Anterior Segment OCT Images: The Chinese American Eye Study

      Purpose : To develop a deep neural network that detects the scleral spur in anterior segment optical coherence tomography (AS-OCT) images. Methods : Participants in the Chinese American Eye Study, a population-based study in Los Angeles, California, underwent complete ocular examinations, including AS-OCT imaging with the Tomey CASIA SS-1000. One human expert grader provided reference labels of scleral spur locations in all images. A convolutional neural network (CNN)-based on the ResNet-18 architecture was developed to detect the scleral spur in each image. Performance of the CNN model was assessed by calculating prediction errors, defined as the difference between the Cartesian coordinates ...

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    5. Advances in Ocular Imaging in Glaucoma (Textbook)

      Advances in Ocular Imaging in Glaucoma (Textbook)

      Serving as a practical guide to the ocular imaging modalities that are currently available to eye care providers for the care of glaucoma patients, this book provides information on advances in ocular imaging and their applications in the diagnosis and management of glaucoma. Each chapter introduces the imaging modality, highlight its strengths and weaknesses for clinical care, and discuss its integration into the clinical examination and decision-making process. The chapters also provide an in-depth description of the interpretation of images from each imaging modality. When appropriate, the chapters will summarize past and ongoing research and propose future research directions and ...

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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. Effect of Scan Size on Glaucoma Diagnostic Performance Using OCT Angiography En Face Images of the Radial Peripapillary Capillaries

      Effect of Scan Size on Glaucoma Diagnostic Performance Using OCT Angiography En Face Images of the Radial Peripapillary Capillaries

      Precis: When comparing 4.5×4.5 mm to 6.0×6.0 mm optical coherence tomography angiography scans of the radial peripapillary capillaries (RPCs) for glaucoma diagnostic capability, there was a trend of 4.5 scans outperforming 6.0 scans, especially for inferior, nasal, and superior quadrants. Objectives: The main purpose of this study was to compare diagnostic ability of peripapillary vessel parameters from 4.5×4.5 mm (4.5) and 6.0×6.0 mm (6.0) spectral-domain optical coherence tomography angiography scans of the RPC in detecting primary open-angle glaucoma from nonglaucoma eyes. Methods: Consecutive patients ...

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    8. Quantitative Evaluation of Gonioscopic and EyeCam Assessments of Angle Dimensions Using Anterior Segment Optical Coherence Tomography

      Quantitative Evaluation of Gonioscopic and EyeCam Assessments of Angle Dimensions Using Anterior Segment Optical Coherence Tomography

      Purpose : To evaluate the relationship between angle dimensions assessed by gonioscopy or EyeCam and anterior segment optical coherence tomography (AS-OCT). Methods : Subjects aged 50 years or older were recruited from the Chinese American Eye Study (CHES). Each subject underwent a complete ocular exam, including gonioscopy, AS-OCT, and EyeCam. Angle closure was defined as three or more quadrants in which pigmented trabecular meshwork could not be visualized. Angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), trabecular iris angle (TIA), and scleral spur angle (SSA) were measured in each AS-OCT image. Results : 709 eyes (272 angle closure ...

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      Mentions: UCLA
    9. Diagnostic Performance of Macular Versus Peripapillary Vessel Parameters by Optical Coherence Tomography Angiography for Glaucoma

      Diagnostic Performance of Macular Versus Peripapillary Vessel Parameters by Optical Coherence Tomography Angiography for Glaucoma

      Purpose : To compare the diagnostic ability of the vessel parameters in macular and peripapillary regions measured using spectral-domain optical coherence tomography angiography (SD-OCTA) in differentiating primary open-angle glaucoma (POAG) from healthy eyes. Methods : POAG patients and healthy subjects underwent 6 × 6-mm scans centered on the macula and optic nerve head. Commercially available automatic segmentation created en face images from SD-OCTA of the superficial retinal layer (SRL) of the macular (m) and peripapillary (cp) regions. Vessel area density (VAD), vessel skeleton density (VSD), vessel complexity index (VCI), and flux were calculated. Area under curve (AUC) statistics controlled for age and intereye ...

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    10. Peripapillary microvasculature in the retinal nerve fiber layer in glaucoma by optical coherence tomography angiography: focal structural and functional correlations and diagnostic performance

      Peripapillary microvasculature in the retinal nerve fiber layer in glaucoma by optical coherence tomography angiography: focal structural and functional correlations and diagnostic performance

      Purpose: To quantify peripapillary microvasculature within the retinal nerve fiber layer (RNFL) in primary open-angle glaucoma (POAG) and normal eyes, determine association of perfusion parameters with structural and functional measures, and report diagnostic accuracy of perfusion parameters. Patients and methods: POAG and normal patients underwent 6×6 mm2 optic nerve head scans (Angioplex optical coherence tomography angiography [OCTA]; Cirrus HD-OCT 5000) and Humphrey Field Analyzer II-i 24-2 visual field (VF) testing. Prototype software performed semiautomatic segmentation to create RNFL en face images and quantified vessel area density (VAD), vessel skeleton density (VSD), and vessel complexity index (VCI) in the optic ...

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    11. Correlation Between Intraocular Pressure and Angle Configuration Measured by Optical Coherence Tomography: The Chinese American Eye Study

      Correlation Between Intraocular Pressure and Angle Configuration Measured by Optical Coherence Tomography: The Chinese American Eye Study

      PURPOSE To characterize the relationship between angle configuration measured by anterior segment optical coherence tomography (AS-OCT) and intraocular pressure (IOP). DESIGN Cross-sectional study. PARTICIPANTS Subjects aged 50 years or older were identified from the Chinese American Eye Study (CHES), a population-based epidemiological study in Los Angeles, CA. METHODS Each subject underwent a complete ocular exam including Goldmann applanation tonometry, gonioscopy, and AS-OCT imaging. Four AS-OCT images were analyzed per eye and parameters describing angle configuration were measured, including angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), trabecular iris angle (TIA), and scleral spur angle (SSA ...

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      Mentions: UCLA
    12. 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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    13. Benefit of Measuring Anterior Segment Structures Using an Increased Number of Optical Coherence Tomography Images: The Chinese American Eye Study

      Benefit of Measuring Anterior Segment Structures Using an Increased Number of Optical Coherence Tomography Images: The Chinese American Eye Study

      Purpose : The purpose of this study was to evaluate the benefit of analyzing an increased number of anterior segment optical coherence tomography (AS-OCT) images on measurement values of various anterior segment parameters. Methods : Subjects for this cross-sectional study were recruited from the Chinese American Eye Study (CHES), a population-based study in Los Angeles, CA. Thirty-two AS-OCT images were acquired from one eye each of 83 consecutive subjects. Sixteen parameters were analyzed in each image, including angle opening distance (AOD), angle recess area (ARA), trabecular iris space area (TISA), trabecular iris angle (TIA), scleral spur angle (SSAngle), lens vault (LV), pupillary ...

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      Mentions: UCLA
    14. 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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    15. 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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    16. 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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    17. 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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    18. 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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    19. Advanced Imaging for Glaucoma Study: Design, Baseline Characteristics, and Inter-Site Comparison

      Advanced Imaging for Glaucoma Study: Design, Baseline Characteristics, and Inter-Site Comparison

      Purpose To report the baseline characteristics of the participants in the Advanced Imaging for Glaucoma Study. To compare the participating sites for variations among subjects and the performance of imaging instruments. Design Multi-center longitudinal observational cohort study Methods A total of 788 participants (1,329 eyes) were enrolled from three academic referral centers. There were 145 participants (289 eyes) in the normal group, 394 participants (663 eyes) in the glaucoma suspect/preperimetric glaucoma group, and 249 participants (377 eyes) in the perimetric glaucoma group. Participants underwent a full clinical exam, standard automated perimetry, and imaging with time-domain and Fourier-domain optical ...

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    20. Combining Information From 3 Anatomic Regions in the Diagnosis of Glaucoma With Time-Domain Optical Coherence Tomography

      Combining Information From 3 Anatomic Regions in the Diagnosis of Glaucoma With Time-Domain Optical Coherence Tomography

      Purpose: To improve the diagnosis of glaucoma by combining time-domain optical coherence tomography (TD-OCT) measurements of the optic disc, circumpapillary retinal nerve fiber layer (RNFL), and macular retinal thickness. Patients and Methods: Ninety-six age-matched normal and 96 perimetric glaucoma participants were included in this observational, cross-sectional study. Or-logic, support vector machine, relevance vector machine, and linear discrimination function were used to analyze the performances of combined TD-OCT diagnostic variables. Results: The area under the receiver-operating curve (AROC) was used to evaluate the diagnostic accuracy and to compare the diagnostic performance of single and combined anatomic variables. The best RNFL thickness ...

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    21. 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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    22. 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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    23. Variation in Optic Nerve and Macular Structure with Age and Race with Spectral-Domain Optical Coherence Tomography

      Variation in Optic Nerve and Macular Structure with Age and Race with Spectral-Domain Optical Coherence Tomography
      Purpose: To evaluate the effects of age and race on optic disc, retinal nerve fiber layer, and macular measurements with spectral-domain optical coherence tomography (SD OCT).Design: Cross-sectional observational study.Participants: Three hundred fifty adult subjects without ocular disease.Methods: Data from SD OCT imaging of the optic nerve head, peripapillary retinal nerve fiber layer (RNFL), and macula of 632 eyes from 350 subjects without ocular disease were imaged with SD OCT. Multivariate models were used to determine the effect of age and race on quantitative measurements of optic disc, RNFL, and macula.Main Outcome Measures: Optic nerve, RNFL, and ...
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    24. 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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    Detection of Macular Ganglion Cell Loss in Glaucoma by Fourier-Domain Optical Coherence Tomography Topographic Differences in the Age-related Changes in the Retinal Nerve Fiber Layer of Normal Eyes Measured by Stratus Optical Coherence Tomography Pilot Study of Optical Coherence Tomography Measurement of Retinal Blood Flow in Retinal and Optic Nerve Diseases Variation in Optic Nerve and Macular Structure with Age and Race with Spectral-Domain Optical Coherence Tomography Relationship among visual field, blood flow, and neural structure measurements in glaucoma Does optic nerve head size variation affect circumpapillary retinal nerve fiber layer thickness measurement by optical coherence tomography? Combining Information From 3 Anatomic Regions in the Diagnosis of Glaucoma With Time-Domain Optical Coherence Tomography In-hospital heart failure in patients with Takotsubo cardiomyopathy due to coronary artery disease: An artificial intelligence and optical coherence tomography study Risk factors for epiretinal membrane formation and peeling following pars plana vitrectomy for primary rhegmatogenous retinal detachment, an OCT guided analysis In vivo tracking of individual stem cells labeled with nanowire lasers using multimodality imaging Spatial resolution in optical coherence elastography of bounded media Detecting vulnerable carotid plaque and its component characteristics: Progress in related imaging techniques