All Articles from Mani Baskaran -Optical Coherence Tomography News

Articles from Mani Baskaran

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1. A Deep Learning System for Automated Angle-Closure Detection in Anterior Segment Optical Coherence Tomography Images
  
  Explore American Journal of Ophthalmology Mar 5 2019 Ophthalmology
  
  Purpose Anterior segment optical coherence tomography (AS-OCT) provides an objective imaging modality for visually identifying anterior segment structures. An automated detection system could assist ophthalmologists in interpreting AS-OCT images for presence of angle closure. Design Development of an artificial intelligence automated detection system for the presence of angle closure. Methods A deep learning system for automated angle-closure detection in AS-OCT images was developed, and this was compared with another automated angle-closure detection system based on quantitative features. A total of 4135 Visante AS-OCT images from 2113 subjects (8270 anterior chamber angle (ACA) images with 7375 open-angle and 895 angle-closure) were ...
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  Mentions: Singapore Eye Research Institute Mani Baskaran Tin Aung
2. Quantitative analysis of choriocapillaris in non-human primates using swept-source optical coherence tomography angiography (SS-OCTA)
  
  Explore OSA | OSA Publishing Dec 26 2018 Ophthalmology
  
  The choriocapillaris is a unique vascular plexus located posterior to the retinal pigment epithelium. In recent years, there is an increasing interest in the examination of the interrelationship between the choriocapillaris and eye diseases. We used several techniques to study choroidal perfusion, including laser Doppler flowmetry, laser speckle flowgraphy, and optical coherence tomography angiography (OCTA), but with the latter no standardized algorithm for quantitative analysis has been provided. We analyzed different algorithms to quantify flow voids in non-human primates that can be easily implemented into clinical research. In-vivo, high-resolution images of the non-human primate choriocapillaris were acquired with a swept-source ...
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  Mentions: Medical University of Vienna Carl Zeiss Meditec Nanyang Technological University
3. Assessment of Circumferential Angle Closure with Swept-Source Optical Coherence Tomography: a community based study
  
  Explore American Journal of Ophthalmology Nov 28 2018 Ophthalmology
  
  Purpose To evaluate the diagnostic performance of swept-source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan) for angle closure detection, in comparison with gonioscopy in a community setting. Design Reliability analysis. Methods A total of 2027 phakic subjects aged ≥50 years, with no previous history of glaucoma, laser (including peripheral iridotomy), intraocular surgery or ocular trauma, were consecutively recruited from a community polyclinic in Singapore. Gonioscopy was performed by a single trained ophthalmologist. SS-OCT angle scans, which obtain radial scans for the entire circumference of the angle, were analyzed by a single examiner, masked to the subject’s ...
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  Mentions: Johns Hopkins University Singapore Eye Research Institute David S. Friedman
4. Role of anterior segment optical coherence tomography in angle closure disease: a review
  
  Explore Wiley Online Library Nov 30 2017 Ophthalmology
  
  This article aims to review the published literature pertaining to the use of anterior segment optical coherence tomography (AS-OCT) in the evaluation of angle closure disease. Searches on the available published literature were last conducted on June 15, 2017. Rated as Level I evidence, we found that AS-OCT has shown good sensitivity and moderate diagnostic accuracy to detect narrow angles when compared with gonioscopy. AS-OCT quantitative and qualitative parameters demonstrated strong association with the presence of gonioscopically closed-angles. This technology provides an objective non-contact method of assessing the angle that is well tolerated by the patient and correlates well with ...
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  Mentions: Singapore Eye Research Institute Mani Baskaran Tin Aung
5. Segmentation and Quantification for Angle-Closure Glaucoma Assessment in Anterior Segment OCT
  
  Explore IEEE Xplore Aug 31 2017 Ophthalmology
  
  Angle-closure glaucoma is a major cause of irreversible visual impairment and can be identified by measuring the anterior chamber angle (ACA) of the eye. The ACA can be viewed clearly through anterior segment optical coherence tomography (AS-OCT), but the imaging characteristics and the shapes and locations of major ocular structures can vary significantly among different AS-OCT modalities, thus complicating image analysis. To address this problem, we propose a data-driven approach for automatic AS-OCT structure segmentation, measurement, and screening. Our technique first estimates initial markers in the eye through label transfer from a hand-labeled exemplar data set, whose images are collected ...
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  Mentions: Singapore Eye Research Institute National University of Singapore Mani Baskaran
6. Feature Of The Week 05/28/2017: In Vivo 3-Dimensional Strain Mapping Confirms Large Optic Nerve Head Deformations Following Horizontal Eye Movements
  
  Explore Optical Coherence Tomography News May 28 2017 Ophthalmology
  
  Glaucoma is characterized by an irreversible damage of retinal ganglion cells within the optic nerve head (ONH) at the back of the eye. Currently we know that elevated intraocular pressure (IOP) is associated with increased prevalence of glaucoma but not all glaucoma patients have an elevated IOP. The biomechanical theory of glaucoma hypothesizes that elevated (or fluctuating) IOP deforms the ONH tissues, including the lamina cribrosa (LC), and that these deformations drive retinal ganglion cell injury and death. However, IOP is not the only load that can deform the ONH. Eye movements have recently been hypothesized to be able to ...
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  Mentions: Duke University University College London National University of Singapore
7. Investigation of the variability of anterior chamber scan protocol with Cirrus high definition optical coherence tomography
  
  Explore Wiley Online Library Jan 18 2017 Ophthalmology
  
  Importance The evaluation of anterior chamber scan (ACS) of Cirrus optical coherence tomography (OCT) for routine clinical use Background To assess the variability of anterior chamber angle (ACA) measurements using the ACS Design Cross-sectional observational study Participants Forty subjects aged 40-80 years Methods One randomly selected eye from 40 subjects was imaged with Cirrus OCT (model 5000, Carl Zeiss Meditec, Dublin, CA) by two different operators (expert vs non-expert) with a 15-minute interval for inter- and intra-observer variability of image acquisition. For image grading, the angle opening distance (AOD750) and the trabecular iris space area (TISA750) of nasal and temporal ...
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  Mentions: National Institutes of Health Singapore Eye Research Institute Carl Zeiss Meditec
8. Evaluation of the Anterior Segment Angle-to-Angle Scan of Cirrus High-Definition Optical Coherence Tomography and Comparison With Gonioscopy and With the Visante OCT
  
  Explore IOVS Journal Jan 10 2017 Ophthalmology
  
  Purpose : To evaluate the diagnostic performance of the anterior segment angle-to-angle scan of the Cirrus high-definition optical coherence tomography (HD-OCT) in detecting eyes with closed angles. Methods : All subjects underwent dark-room gonioscopy by an ophthalmologist. A technician performed anterior segment imaging with Cirrus ( n = 202) and Visante OCT ( n = 85) under dark-room conditions. All eyes were categorized by two masked graders as per number of closed quadrants. Each quadrant of anterior chamber angle was categorized as a closed angle if posterior trabecular meshwork could not be seen on gonioscopy or if there was any irido-corneal contact anterior to scleral spur ...
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  Mentions: Singapore Eye Research Institute National University of Singapore Zeiss Cirrus HD-OCT
9. In Vivo 3-Dimensional Strain Mapping Confirms Large Optic Nerve Head Deformations Following Horizontal Eye Movements
  
  Explore IOVS Journal Oct 12 2016 Ophthalmology
  
  Purpose : To measure lamina cribrosa (LC) strains (deformations) following abduction and adduction in healthy subjects and to compare them with those resulting from a relatively high acute intraocular pressure (IOP) elevation. Methods : A total of 16 eyes from 8 healthy subjects were included. Among the 16 eyes, 11 had peripapillary atrophy (PPA). For each subject, both optic nerve heads (ONHs) were imaged using optical coherence tomography (OCT) at baseline (twice), in different gaze positions (adduction and abduction of 20°) and following an acute IOP elevation of approximately 20 mm Hg from baseline (via ophthalmodynamometry). Strains of LC for all loading ...
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  Mentions: National University of Singapore Mani Baskaran Tin Aung
10. Determinants of Optical Coherence Tomography–Derived Minimum Neuroretinal Rim Width in a Normal Chinese Population
  
  Explore IOVS Journal May 30 2015 Ophthalmology
  
  Purpose. To characterize an optical coherence tomography (OCT)–derived parameter, Bruch's membrane opening–minimum rim width (BMO-MRW), and its association with demographic and clinical parameters in normal Chinese subjects. Methods. Right eyes of 466 consecutive healthy subjects from a population-based study of Singaporean Chinese underwent Cirrus OCT imaging. The retinal internal limiting membrane (ILM) and BMO were automatically delineated using the built-in Cirrus algorithm. The standard 36 interpolated radial B-scans (72 BMO points, 5° increments) of each optic nerve head were manually extracted from the central circle (3.46-mm diameter). We used Matlab to measure the shortest distance from ...
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  Mentions: Duke University Singapore Eye Research Institute Zeiss Cirrus HD-OCT
11. Lamina Cribrosa Visibility using Optical Coherence Tomography: Comparison of Devices and Effects of Image Enhancement Techniques
  
  Explore iovs.org Jan 17 2015 Ophthalmology
  
  Purpose: To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC). Methods: A horizontal B-scan was acquired through the centre of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. AC was applied post-acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1,200 images in a randomised sequence. The anterior LC was graded from 0 to 4 ...
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  Mentions: University College London Singapore Eye Research Institute National University of Singapore
12. Swept-source optical coherence tomography assessment of iris-trabecular contact after phacoemulsification with or without goniosynechialysis in eyes with primary angle closure glaucoma
  
  Explore BJO Online Jan 8 2015 Ophthalmology
  
  Aims To compare the change in iris–trabecular contact (ITC) area using swept-source optical coherence tomography (SS-OCT) in eyes with primary angle closure glaucoma (PACG) and cataract that underwent phacoemulsification (PE) with intraocular lens implantation alone compared with PE with goniosynechialysis (GSL). Methods One eye of 22 patients with PACG with peripheral anterior synechiae (PAS) detected by indentation gonioscopy was randomised into two groups (PE alone (n=11) and PE+GSL (n=11)). The anterior chamber angles were evaluated by SS-OCT under dark conditions before and 12 months after surgery using the three-dimensional angle analysis scan protocol that simultaneously obtains ...
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  Mentions: Singapore Eye Research Institute National University of Singapore Tin Aung
13. Sectoral variations of iridocorneal angle width and iris volume in Chinese Singaporeans: a swept-source optical coherence tomography study
  
  Explore Home - Springer May 4 2014 Ophthalmology
  
  Purpose To assess variations in the iridocorneal angle width and iris volume in Chinese subjects using swept-source optical coherence tomography (SS-OCT). Methods Consecutive subjects, aged 40–80 years, with no previous ophthalmic problems were recruited from a population-based study of Chinese Singaporeans. All subjects underwent 360° SS-OCT (SS-1000 CASIA, Tomey Corporation, Nagoya, Japan) angle imaging and gonioscopy in one randomly selected eye in the dark. For each eye, 16 frames (11.25° apart) were selected for analysis from 128 cross-sectional images, and measurements of the trabecular iris space area 750 μm from the scleral spur (TISA750) and iris volume were ...
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  Mentions: Singapore Eye Research Institute National University of Singapore Tomey Corporation
14. Development of a Score and Probability Estimate for Detecting Angle Closure Based on Anterior Segment Optical Coherence Tomography
  
  Explore American Journal of Ophthalmology Nov 12 2013 Ophthalmology
  
  Purpose To develop a score along with an estimated probability of disease for detecting angle closure based on anterior segment optical coherence tomography (AS OCT) imaging. Design Cross-sectional study. Methods A total of 2047 subjects 50 years of age and older were recruited from a community polyclinic in Singapore. All subjects underwent standardized ocular examination including gonioscopy and imaging by AS OCT (Carl Zeiss Meditec). Customized software (Zhongshan Angle Assessment Program) was used to measure AS OCT parameters. Complete data were available for 1368 subjects. Data from the right eyes were used for analysis. A stepwise logistic regression model with ...
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  Mentions: Johns Hopkins University Singapore Eye Research Institute David S. Friedman
15. Anterior Segment Optical Coherence Tomography Parameters in Subtypes of Primary Angle Closure
  
  Explore iovs.org Jun 21 2013 Ophthalmology
  
  Purpose: To compare anterior segment parameters, assessed by anterior segment optical coherence tomography (ASOCT), in subjects categorized as primary angle closure suspect (PACS), primary angle closure (PAC), primary angle closure glaucoma (PACG), and previous acute PAC (APAC); and to identify factors associated with APAC. Methods: This was a prospective ASOCT study of 425 subjects with angle closure (176 PACS, 66 PAC, 125 PACG, and 58 APAC). Customized software (Zhongshan Angle Assessment Program, Guangzhou, China) was used to measure ASOCT parameters, including angle opening distance (AOD750), trabecular-iris space area (TISA750), anterior chamber depth, width, area and volume (ACD, ACW, ACA, ACV ...
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  Mentions: Singapore Eye Research Institute Mani Baskaran Tin Aung
16. Assessment of Circumferential Angle-Closure by the Iris–Trabecular Contact Index with Swept-Source Optical Coherence Tomography
  
  Explore Ophthalmology Jun 16 2013 Ophthalmology
  
  Purpose To evaluate the diagnostic performance of the iris–trabecular contact (ITC) index, a measure of the degree of angle-closure, using swept-source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan) in comparison with gonioscopy. Design Prospective observational study. Participants A total of 108 normal subjects and 32 subjects with angle-closure. Methods The SSOCT 3-dimensional angle scans, which obtain radial scans for the entire circumference of the angle, were performed under dark conditions and analyzed using customized software by a single examiner masked to the subjects' clinical details. The ITC index was calculated as a percentage of the angle ...
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  Mentions: Johns Hopkins University Singapore Eye Research Institute David S. Friedman
17. Assessment of trabecular meshwork width using swept source optical coherence tomography
  
  Explore Home - Springer Feb 26 2013 Ophthalmology
  
  Purpose Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 μm from the scleral spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement. Methods Participants underwent gonioscopy and SS-OCT imaging in the dark. High-definition SS-OCT images were corrected for refractive distortion; and customized software (ImageJ; National Institutes of Health, Bethesda, MD, USA) was utilized ...
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  Mentions: Johns Hopkins University National Institutes of Health Singapore Eye Research Institute
18. Automatic segmentation of the choroid in enhanced depth imaging optical coherence tomography images
  
  Explore opticsinfobase.org Feb 16 2013 Ophthalmology
  
  Enhanced Depth Imaging (EDI) optical coherence tomography (OCT) provides high-definition cross-sectional images of the choroid in vivo, and hence is used in many clinical studies. However, the quantification of the choroid depends on the manual labelings of two boundaries, Bruch’s membrane and the choroidal-scleral interface. This labeling process is tedious and subjective of inter-observer differences, hence, automatic segmentation of the choroid layer is highly desirable. In this paper, we present a fast and accurate algorithm that could segment the choroid automatically. Bruch’s membrane is detected by searching the pixel with the biggest gradient value above the retinal pigment ...
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  Mentions: Singapore Eye Research Institute Nanyang Technological University Mani Baskaran
19. Relationship Between Intraocular Pressure and Angle Configuration: An Anterior Segment OCT Study
  
  Explore iovs.org Jan 9 2013 Ophthalmology
  
  Purpose: To assess the relationship between intra-ocular pressure (IOP) and anterior chamber angle (ACA) configuration as assessed by gonioscopy and anterior segment optical coherence tomography (AS-OCT). Methods: 2045 subjects aged 50 years and over, recruited from a community clinic, underwent AS-OCT, Goldmann applanation tonometry, and gonioscopy. A quadrant was classified as closed on gonioscopy if the posterior trabecular meshwork could not be seen. A closed quadrant on AS-OCT was defined by the presence of any contact between the iris and angle wall anterior to the scleral spur. Customized software (Zhongshan Angle Assessment Program, Guangzhou, China) was used to measure AS-OCT ...
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  Mentions: Singapore Eye Research Institute Sun Yat-Sen University Tien Yin Wong
20. Classification Algorithms Based on Anterior Segment Optical Coherence Tomography Measurements for Detection of Angle Closure
  
  Explore Ophthalmology Sep 23 2012 Ophthalmology
  
  Objective: A recent study found that a combination of 6 anterior segment optical coherence tomography (ASOCT) parameters (anterior chamber area, volume, and width [ACA, ACV, ACW], lens vault [LV], iris thickness at 750 μm from the scleral spur, and iris cross-sectional area) explain >80% of the variability in angle width. The aim of this study was to evaluate classification algorithms based on ASOCT measurements for the detection of gonioscopic angle closure.Design: Cross-sectional study.Participants: We included 2047 subjects aged ≥50 years.Methods: Participants underwent gonioscopy and ASOCT (Carl Zeiss Meditec, Dublin, CA). Customized software (Zhongshan Angle Assessment Program, Guangzhou ...
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  Mentions: Johns Hopkins University Singapore Eye Research Institute David S. Friedman
21. Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure
  
  Explore SpringerLink Home Sep 22 2012 Ophthalmology
  
  Purpose To evaluate the inter- and intra-observer agreement of measurement of the iris–trabecular contact (ITC) index, a measure of the degree of angle closure, using swept source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan). Methods One randomly selected eye of 60 subjects was imaged under dark room conditions. The SSOCT 3-dimensional angle scan simultaneously obtains 128 radial scans of the anterior chamber for the entire circumference of the angle. Post-imaging analysis estimated the ITC index using in-built software. For intra-observer agreement for image grading, one examiner performed the grading twice in a masked fashion and random ...
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  Mentions: Johns Hopkins University David S. Friedman Tomey Corporation
22. Comparison of EyeCam and anterior segment optical coherence tomography in detecting angle closure
  
  Explore Wiley Online Library Sep 4 2012 Ophthalmology
  
  Purpose: To compare the diagnostic performance of EyeCam (Clarity Medical Systems, Pleasanton, CA, USA) and anterior segment optical coherence tomography (ASOCT, Visante; Carl Zeiss Meditec, Dublin, CA, USA) in detecting angle closure, using gonioscopy as the reference standard. Methods: Ninety-eight phakic patients, recruited from a glaucoma clinic, underwent gonioscopy by a single examiner, and EyeCam and ASOCT imaging by another examiner. Another observer, masked to gonioscopy findings, graded EyeCam and ASOCT images. For both gonioscopy and EyeCam, a closed angle in a particular quadrant was defined if the posterior trabecular meshwork was not visible. For ASOCT, angle closure was defined ...
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  Mentions: Johns Hopkins University Singapore Eye Research Institute David S. Friedman
23. Automatic measurements of choroidal thickness in EDI-OCT images
  
  Explore IEEE Xplore Sep 1 2012 Ophthalmology
  
  Enhanced Depth Imaging (EDI) optical coherence tomography (OCT) provides high-definition cross-sectional images of the choroid in vivo, and hence is used in many clinical studies. However, measurement of choroidal thickness depends on the manual labeling, which is tedious and subjective of inter-observer differences. In this paper, we propose a fast and accurate algorithm that could measure the choroidal thickness automatically. The lower boundary of the choroid is detected by searching the biggest gradient value above the retinal pigment epithelium (RPE) and the upper boundary is formed by finding the shortest path of the graph formed by valley pixels using dynamic ...
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  Mentions: Nanyang Technological University Mani Baskaran Tin Aung
24. Determinants of Ganglion Cell–Inner Plexiform Layer Thickness Measured by High-Definition Optical Coherence Tomography
  
  Explore iovs.org Aug 25 2012 Ophthalmology
  
  Purpose. To determine the distribution, variation, and determinants of ganglion cell–inner plexiform layer (GC-IPL) thickness in nonglaucomatous eyes measured by high-definition optical coherence tomography (HD-OCT). Methods. Six hundred twenty-three Chinese adults aged 40 to 80 years were consecutively recruited from a population-based study. All subjects underwent a standardized interview, ophthalmic examination, and automated perimetry. HD-OCT with macular cube protocol was used to measure the GC-IPL thickness. Univariate and multiple linear regression analyses were performed to examine the relationship between GC-IPL thickness with ocular and systemic factors. Results. The mean (±SD) age of study subjects was 52.84 ± 6.14 ...
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  Mentions: Singapore Eye Research Institute Carl Zeiss Meditec University of Melbourne
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