1. Articles from Tin A. Tun

    1-24 of 29 1 2 »
    1. Evaluation of meridional scans for angle closure assessment with anterior segment swept-source optical coherence tomography

      Evaluation of meridional scans for angle closure assessment with anterior segment swept-source optical coherence tomography

      Background/aims As swept-source optical coherence tomography (SS-OCT) simultaneously obtains 128 meridional scans, it is important to identify which scans are playing the main role in classifying gonioscopic angle closure to simplify the analysis. We aimed to evaluate the diagnostic performance of every meridional scan in its ability to detect gonioscopic angle closure. Methods Observational study with 2027 phakic subjects consecutively recruited from a community polyclinic. Gonioscopy and SS-OCT were performed. Gonioscopic angle closure was defined as non-visibility of the posterior trabecular meshwork in ≥180° of the angle, while SS-OCT was defined as iridotrabecular contact anterior to the scleral spur ...

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    2. Towards Label-Free 3D Segmentation of Optical Coherence Tomography Images of the Optic Nerve Head Using Deep Learning

      Towards Label-Free 3D Segmentation of Optical Coherence Tomography Images of the Optic Nerve Head Using Deep Learning

      Since the introduction of optical coherence tomography (OCT), it has been possible to study the complex 3D morphological changes of the optic nerve head (ONH) tissues that occur along with the progression of glaucoma. Although several deep learning (DL) techniques have been recently proposed for the automated extraction (segmentation) and quantification of these morphological changes, the device-specific nature and the difficulty in preparing manual segmentations (training data) limit their clinical adoption. With several new manufacturers and next-generation OCT devices entering the market, the complexity in deploying DL algorithms clinically is only increasing. To address this, we propose a DLbased 3D ...

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    3. Anterior Segment Optical Coherence Tomography: Is There a Clinical Role in the Management of Primary Angle Closure Disease?

      Anterior Segment Optical Coherence Tomography: Is There a Clinical Role in the Management of Primary Angle Closure Disease?

      Primary angle closure disease (PACD) covers a spectrum that includes primary angle closure suspect, primary angle closure, primary angle closure glaucoma, and acute primary angle closure. Accumulating evidence suggests that the pathogenesis of PACD is complex, with multiple contributory factors including variations in the anatomic or biometric characteristics of the angle segment structures. Advances in anterior segment optical coherence tomography technology have further enhanced our understanding of the risk factors and mechanisms involved in the disease process. This review discusses the potential clinical role of the anterior segment optical coherence tomography in the diagnosis, mechanistic evaluation, and as a predictor ...

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    4. A Deep Learning Approach to Denoise Optical Coherence Tomography Images of the Optic Nerve Head

      A Deep Learning Approach to Denoise Optical Coherence Tomography Images of the Optic Nerve Head

      Optical coherence tomography (OCT) has become an established clinical routine for the in vivo imaging of the optic nerve head (ONH) tissues, that is crucial in the diagnosis and management of various ocular and neuro-ocular pathologies. However, the presence of speckle noise affects the quality of OCT images and its interpretation. Although recent frame-averaging techniques have shown to enhance OCT image quality, they require longer scanning durations, resulting in patient discomfort. Using a custom deep learning network trained with 2,328 ‘clean B-scans’ (multi-frame B-scans; signal averaged), and their corresponding ‘noisy B-scans’ (clean B-scans + Gaussian noise), we were able to ...

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    5. Understanding diagnostic disagreement in angle closure assessment between anterior segment optical coherence tomography and gonioscopy

      Understanding diagnostic disagreement in angle closure assessment between anterior segment optical coherence tomography and gonioscopy

      Background/aims Although being a more objective tool for assessment and follow-up of angle closure, reliability studies have reported a moderate diagnostic performance for anterior segment optical coherence tomography (OCT) technologies when comparing with gonioscopy as the reference standard. We aim to determine factors associated with diagnostic disagreement in angle closure when assessed by anterior segment swept source OCT (SS-OCT, CASIA SS-1000; Tomey, Nagoya, Japan) and gonioscopy. Methods Cross-sectional study. A total of 2027 phakic subjects aged ≥50 years, with no relevant previous ophthalmic history, were consecutively recruited from a community polyclinic in Singapore. Gonioscopy and SS-OCT (128 radial scans ...

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    6. A Deep Learning System for Automated Angle-Closure Detection in Anterior Segment Optical Coherence Tomography Images

      A Deep Learning System for Automated Angle-Closure Detection in Anterior Segment Optical Coherence Tomography Images

      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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    7. Assessment of Circumferential Angle Closure with Swept-Source Optical Coherence Tomography: a community based study

      Assessment of Circumferential Angle Closure with Swept-Source Optical Coherence Tomography: a community based study

      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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    8. A Deep Learning Approach to Denoise Optical Coherence Tomography Images of the Optic Nerve Head

      A Deep Learning Approach to Denoise Optical Coherence Tomography Images of the Optic Nerve Head

      Purpose: To develop a deep learning approach to de-noise optical coherence tomography (OCT) B-scans of the optic nerve head (ONH). Methods: Volume scans consisting of 97 horizontal B-scans were acquired through the center of the ONH using a commercial OCT device (Spectralis) for both eyes of 20 subjects. For each eye, single-frame (without signal averaging), and multi-frame (75x signal averaging) volume scans were obtained. A custom deep learning network was then designed and trained with 2,328 "clean B-scans" (multi-frame B-scans), and their corresponding "noisy B-scans" (clean B-scans + gaussian noise) to de-noise the single-frame B-scans. The performance of the de-noising ...

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    9. Quantification of the Posterior Cornea Using Swept Source Optical Coherence Tomography

      Quantification of the Posterior Cornea Using Swept Source Optical Coherence Tomography

      Purpose : We define optical coherence tomography (OCT) measurement parameters of the corneal endothelium/Descemet's membrane (DM) complex and peripheral transition zone (TZ) and describe these measurements in an ethnically Chinese population. Methods : OCT images of the anterior segment and iridocorneal angle were obtained from 129 healthy Chinese subjects (129 eyes), aged 40 to 81 years. The scleral spur (SS) and Schwalbe's line (SL) were identified in each image. Endothelium/DM diameter, referred to as endothelial arc length (EAL), is the SL-to-SL distance. The SS-to-SL distance encompasses the TZ and trabecular meshwork (TM). Since the TZ cannot be visualized ...

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    10. DRUNET: a dilated-residual U-Net deep learning network to segment optic nerve head tissues in optical coherence tomography images

      DRUNET: a dilated-residual U-Net deep learning network to segment optic nerve head tissues in optical coherence tomography images

      Given that the neural and connective tissues of the optic nerve head (ONH) exhibit complex morphological changes with the development and progression of glaucoma, their simultaneous isolation from optical coherence tomography (OCT) images may be of great interest for the clinical diagnosis and management of this pathology. A deep learning algorithm (custom U-NET) was designed and trained to segment 6 ONH tissue layers by capturing both the local (tissue texture) and contextual information (spatial arrangement of tissues). The overall Dice coefficient (mean of all tissues) was 0.91 ± 0.05 when assessed against manual segmentations performed by an expert observer ...

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    11. DRUNET: A Dilated-Residual U-Net Deep Learning Network to Digitally Stain Optic Nerve Head Tissues in Optical Coherence Tomography Images

      DRUNET: A Dilated-Residual U-Net Deep Learning Network to Digitally Stain Optic Nerve Head Tissues in Optical Coherence Tomography Images

      Given that the neural and connective tissues of the optic nerve head (ONH) exhibit complex morphological changes with the development and progression of glaucoma, their simultaneous isolation from optical coherence tomography (OCT) images may be of great interest for the clinical diagnosis and management of this pathology. A deep learning algorithm was designed and trained to digitally stain (i.e. highlight) 6 ONH tissue layers by capturing both the local (tissue texture) and contextual information (spatial arrangement of tissues). The overall dice coefficient (mean of all tissues) was 0.91 ± 0.05 when assessed against manual segmentations performed by an ...

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    12. A Deep Learning Approach to Digitally Stain Optical Coherence Tomography Images of the Optic Nerve Head

      A Deep Learning Approach to Digitally Stain Optical Coherence Tomography Images of the Optic Nerve Head

      Purpose. To develop a deep learning approach to digitally-stain optical coherence tomography (OCT) images of the optic nerve head (ONH). Methods. A horizontal B-scan was acquired through the center of the ONH using OCT (Spectralis) for 1 eye of each of 100 subjects (40 normal & 60 glaucoma). All images were enhanced using adaptive compensation. A custom deep learning network was then designed and trained with the compensated images to digitally stain (i.e. highlight) 6 tissue layers of the ONH. The accuracy of our algorithm was assessed (against manual segmentations) using the Dice coefficient, sensitivity, and specificity. We further studied ...

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    13. Investigation of the variability of anterior chamber scan protocol with Cirrus high definition optical coherence tomography

      Investigation of the variability of anterior chamber scan protocol with Cirrus high definition optical coherence tomography

      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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    14. 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

      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

      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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    15. Association of iris surface features with iris parameters assessed by swept-source optical coherence tomography in Asian eyes

      Association of iris surface features with iris parameters assessed by swept-source optical coherence tomography in Asian eyes

      Background/aims To characterise the association of iris surface features (crypts, furrows and colour) with iris volume and curvature assessed by swept-source optical coherence tomography (SSOCT) in Asian eyes. Methods Iris crypts (by number and size) and furrows (by number and circumferential extent) were graded from iris photographs. Iris colour was measured by a customised algorithm written on MATLAB (MathWorks, Natick, Massachusetts, USA). The iris was imaged by SSOCT (SS-1000, CASIA, Tomey, Nagoya, Japan). The associations of surface features with iris parameters were analysed using a generalised estimating equation. Results A total of 1704 subjects (3297 eyes) were included in ...

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    16. Determinants of Optical Coherence Tomography–Derived Minimum Neuroretinal Rim Width in a Normal Chinese Population

      Determinants of Optical Coherence Tomography–Derived Minimum Neuroretinal Rim Width in a Normal Chinese Population

      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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    17. Repeatability of tear meniscus evaluation using spectral-domain Cirrus® HD-OCT and time-domain Visante® OCT

      Repeatability of tear meniscus evaluation using spectral-domain Cirrus® HD-OCT and time-domain Visante® OCT

      Purpose To investigate the intra-rater, inter-rater and inter-device repeatability of a spectral-domain OCT (Cirrus) and a time-domain OCT (Visante) for tear meniscus height (TMH) and area (TMA) measurements. Methods 20 participants with no known eye disease were recruited. Both eyes of participants were imaged with both OCTs under the similar conditions. The inferior tear meniscus was imaged at 6 o’clock position whereas the superior meniscus was imaged at 12 o’clock position. Data from the right eyes was analyzed. Two raters independently measured TMH and TMA using the OCT images, and one rater repeated the measurements. Intra-rater, inter-rater and ...

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    18. Lamina Cribrosa Visibility using Optical Coherence Tomography: Comparison of Devices and Effects of Image Enhancement Techniques

      Lamina Cribrosa Visibility using Optical Coherence Tomography: Comparison of Devices and Effects of Image Enhancement Techniques

      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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    19. Swept-source optical coherence tomography assessment of iris-trabecular contact after phacoemulsification with or without goniosynechialysis in eyes with primary angle closure glaucoma

      Swept-source optical coherence tomography assessment of iris-trabecular contact after phacoemulsification with or without goniosynechialysis in eyes with primary angle closure glaucoma

      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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    20. Sectoral variations of iridocorneal angle width and iris volume in Chinese Singaporeans: a swept-source optical coherence tomography study

      Sectoral variations of iridocorneal angle width and iris volume in Chinese Singaporeans: a swept-source optical coherence tomography study

      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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    21. Assessment of Circumferential Angle-Closure by the Iris–Trabecular Contact Index with Swept-Source Optical Coherence Tomography

      Assessment of Circumferential Angle-Closure by the Iris–Trabecular Contact Index with Swept-Source Optical Coherence Tomography

      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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    22. Assessment of trabecular meshwork width using swept source optical coherence tomography

      Assessment of trabecular meshwork width using swept source optical coherence tomography

      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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    23. Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure

      Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure

      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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    24. Comparison of EyeCam and anterior segment optical coherence tomography in detecting angle closure

      Comparison of EyeCam and anterior segment optical coherence tomography in detecting angle closure

      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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    Novel anterior-chamber angle measurements by high-definition optical coherence tomography using the Schwalbe line as the landmark Imaging of the Iridocorneal Angle with the RTVue Spectral Domain Optical Coherence Tomography Comparison of two spectral domain optical coherence tomography devices for angle closure assessment Comparison of Two Spectral Domain Optical Coherence Tomography Devices for Angle-Closure Assessment Comparison of EyeCam and anterior segment optical coherence tomography in detecting angle closure Swept source optical coherence tomography measurement of the iris–trabecular contact (ITC) index: a new parameter for angle closure Assessment of trabecular meshwork width using swept source optical coherence tomography Assessment of Circumferential Angle-Closure by the Iris–Trabecular Contact Index with Swept-Source Optical Coherence Tomography Determinants of Optical Coherence Tomography–Derived Minimum Neuroretinal Rim Width in a Normal Chinese Population DRUNET: A Dilated-Residual U-Net Deep Learning Network to Digitally Stain Optic Nerve Head Tissues in Optical Coherence Tomography Images Carotid Disease and Retinal Optical Coherence Tomography Angiography Parameters in Type 2 Diabetes: The Fremantle Diabetes Study Phase II Retinal Vascular Density on Optical Coherence Tomography Angiography and Age-related Central and Peripheral Hearing Loss in a Southern Italian Older Population