1. Articles from Tin Aung

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    1. Evaluation of Ocular Biometric and Optical Coherence Tomography Parameters in Preterm Children Without Retinopathy of Prematurity

      Evaluation of Ocular Biometric and Optical Coherence Tomography Parameters in Preterm Children Without Retinopathy of Prematurity

      Purpose: To evaluate and compare biometric and optical coherence tomography parameters of ocular structures in preterm children without retinopathy of prematurity with term children. Methods: A cross-sectional, comparative study was carried out from 2018 to 2019. In this study, 124 eyes of 62 preterm children were compared with 132 eyes of 66 term children aged between 7 and 9 years. Preterm children were born at 28 to 32 weeks with a birth weight of less than 2 kg with no ocular abnormalities, and term children were delivered at 37 or greater weeks and had a birth weight of 2 kg ...

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    2. Angle closure extent, anterior segment dimensions and intraocular pressure

      Angle closure extent, anterior segment dimensions and intraocular pressure

      Aim To investigate the association between the extent of iridotrabecular contact and other quantitative anterior segment dimensions measured by swept-source optical coherence tomography (SS-OCT; CASIA SS-1000, Tomey, Nagoya, Japan) with intraocular pressure (IOP). Methods Cross-sectional study. All subjects who were ≥50 years with no history of glaucoma, ocular surgery or trauma, underwent SS-OCT imaging (eight equally spaced radial scans), Goldman applanation tonometry and gonioscopy on the same day. We measured iridotrabecular contact (ITC) index and area, total volume of trabeculo-iris space area and angle opening distance at 500 and 750 from the scleral spur (TISA 500 and 750, AOD 500 ...

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    3. The Three-Dimensional Structural Configuration of the Central Retinal Vessel Trunk and Branches as a Glaucoma Biomarker

      The Three-Dimensional Structural Configuration of the Central Retinal Vessel Trunk and Branches as a Glaucoma Biomarker

      Purpose : To assess whether the three-dimensional (3D) structural configuration of the central retinal vessel trunk and its branches (CRVT&B) could be used as a diagnostic marker for glaucoma. Design : Retrospective, deep-learning approach diagnosis study. Method : We trained a deep learning network to automatically segment the CRVT&B from the B-scans of the optical coherence tomography (OCT) volume of the optic nerve head (ONH). Subsequently, two different approaches were used for glaucoma diagnosis using the structural configuration of the CRVT&B as extracted from the OCT volumes. In the first approach, we aimed to provide a diagnosis using only 3D ...

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    4. Non-optical coherence tomography modalities for assessment of angle closure

      Non-optical coherence tomography modalities for assessment of angle closure

      Primary angle closure glaucoma is a leading cause of irreversible blindness, particularly in Asia. Its pathophysiology is based in the closure of the anterior chamber angle (ACA). In addition to gonioscopy (current reference standard), in the past decade, anterior segment optical coherence tomography (AS-OCT) has been incorporated in routine ophthalmic practice to help assess the configuration of the ACA. Especially in nonspecialist ophthalmology practice, gonioscopy may be less frequently performed and AS-OCT may not be available, leading to the need of other anterior segment evaluation methods. Evaluating the anterior chamber depth (ACD) has long been recognized as screening tool for ...

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    5. Combining OCT and OCTA for Focal Structure-Function Modeling in Early Primary Open-Angle Glaucoma

      Combining OCT and OCTA for Focal Structure-Function Modeling in Early Primary Open-Angle Glaucoma

      Purpose: To investigate modeling of the focal visual field (VF) loss by combining structural measurements and vascular measurements in eyes with early primary open-angle glaucoma (POAG). Methods: In this cross-sectional study, subjects with early glaucoma (VF mean deviation, ≥-6 dB) underwent optical coherence tomography (OCT) imaging, optical coherence tomography angiography (OCTA) imaging, and Humphrey 24-2 VF tests. Capillary perfusion densities (CPDs) were calculated after the removal of large vessels in the OCTA images. Focal associations between VF losses at the individual VF test locations, circumpapillary retinal nerve fiber layer (RNFL) thickness measurements from OCT, and CPDs were determined using nerve ...

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    6. 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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    7. Digital Gonioscopy based on Three-dimensional Anterior Segment Optical Coherence Tomography: an international multicenter study

      Digital Gonioscopy based on Three-dimensional Anterior Segment Optical Coherence Tomography: an international multicenter study

      Objective: To develop and evaluate the performance of a three-dimensional deep-learning based automated digital gonioscopy system (3D DGS) in detecting two major characteristics in eyes suspected to have primary angle closure glaucoma (PACG): 1) narrow iridocorneal angles (static gonioscopy, Task I) and; 2) peripheral anterior synechiae (PAS) (dynamic gonioscopy, Task II) on optical coherence tomography scans. Design: International cross-sectional multicentre study. Subjects: A total of 1.112 million images of 8694 volume scans (2294 patients) from three centers were included in this study (Task I: training/internal validation/external testing - 4515, 1101, 2222 volume scans respectively; Task II: training/internal ...

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    8. Multi-modal Machine Learning using Visual Fields and Peripapillary Circular OCT Scans in Detection of Glaucomatous Optic Neuropathy

      Multi-modal Machine Learning using Visual Fields and Peripapillary Circular OCT Scans in Detection of Glaucomatous Optic Neuropathy

      Purpose: To develop and test a multi-modal artificial intelligence (AI) algorithm, FusionNet, using the pattern deviation probability plots (PDPs) from visual field (VF) reports and circular peripapillary optical coherence tomography (OCT) to detect glaucomatous optic neuropathy (GON). Design: Cross-sectional study. Subjects: A total of 2463 pairs of VF and OCT images from 1083 patients. Methods: A novel deep learning algorithm (FusionNet) based on bimodal input of VF-OCT paired data was developed to detect GON. VF data were collected using Humphrey Field Analyzer (HFA). OCT images were collected from three types of devices (DRI-OCT, Cirrus OCT and Spectralis OCT). A total ...

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    9. Evaluation of the diagnostic performance of swept-source anterior segment optical coherence tomography in primary angle closure disease

      Evaluation of the diagnostic performance of swept-source anterior segment optical coherence tomography in primary angle closure disease

      Purpose To evaluate the diagnostic performance of swept-source anterior segment optical coherence tomography (SS-OCT) in differentiating primary angle closure diseases (PACD) from control eyes, as well as primary angle closure (PAC) and primary angle closure glaucoma (PACG) from primary angle closure suspect (PACS) eyes. Design Multi-center cross-sectional study. Methods Chinese patients were classified into control, PACS and PAC/PACG groups. Area under the receiving operating characteristics curve (AUC) from logistic regression models was used to evaluate discriminating ability. Sensitivity and specificity were calculated and performance of the models was validated using an independent dataset. Results A total of 2,928 ...

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    10. Repeatability and Reproducibility of Anterior Chamber Angle Measurement with Swept-Source Optical Coherence Tomography in Patients with Primary Angle Closure Suspect

      Repeatability and Reproducibility of Anterior Chamber Angle Measurement with Swept-Source Optical Coherence Tomography in Patients with Primary Angle Closure Suspect

      Purpose : To evaluate the inter- and intra-observer reliability of anterior chamber (AC) angle measurements obtained by swept-source optical coherence tomography (SS-OCT). Methods: Forty-eight consecutive patients diagnosed with primary angle closure suspect (PACS) were included. Three masked observers at different training levels (one glaucoma specialist, one ophthalmology resident, and one pre-medical college student) measured 192 SS-OCT images of the PACS patients. One observer (the glaucoma specialist) repeated measurements 1 week later. SS-OCT parameters included: Anterior segment volume, including corneal, AC, and iris volume; anterior segment dimensions, including AC depth and width (ACD, ACW), and lens vault (LV); and angle parameters, including ...

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    11. Diagnostic accuracy of swept source optical coherence tomography classification algorithms for detection of gonioscopic angle closure

      Diagnostic accuracy of swept source optical coherence tomography classification algorithms for detection of gonioscopic angle closure

      Purpose To evaluate the performance of swept source optical coherence tomography (SS-OCT) to detect gonioscopic angle closure using different classification algorithms. Methods This was a cross-sectional study of 2028 subjects without ophthalmic symptoms recruited from a community-based clinic. All subjects underwent gonioscopy and SS-OCT (Casia, Tomey Corporation, Nagoya, Japan) under dark room conditions. For each eye, 8 out of 128 frames (22.5° interval) were selected to measure anterior chamber parameters namely anterior chamber width, depth, area and volume (ACW, ACD, ACA, and ACV), lens vault (LV), iris curvature (IC), iris thickness (IT) from 750 µm and 2000 µm from ...

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    12. The Effect of Medical Lowering of Intraocular Pressure on Peripapillary and Macular Blood Flow as Measured by Optical Coherence Tomography Angiography in Treatment-naïve Eyes

      The Effect of Medical Lowering of Intraocular Pressure on Peripapillary and Macular Blood Flow as Measured by Optical Coherence Tomography Angiography in Treatment-naïve Eyes

      Prcis: Reduction of intraocular pressure by latanoprost in treatment-naïve eyes is significantly correlated to an increase in vessel density at the optic nerve head. Purpose: To evaluate the effect of topical latanoprost on ocular microvasculature using optical coherence tomography angiography (OCTA). Patients and methods: In this prospective case-control study, 26 eyes from 18 treatment-naïve subjects in whom prostaglandin analogue (PGA) latanoprost 0.005% was initiated, were included as cases. In 10 out of the 18 subjects, medication was initiated in only one eye; their contralateral untreated eyes were used as controls. OCTA (AngioVue®, Optovue inc., Fremont, California, USA ...

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    13. OCT-GAN: single step shadow and noise removal from optical coherence tomography images of the human optic nerve head

      OCT-GAN: single step shadow and noise removal from optical coherence tomography images of the human optic nerve head

      Speckle noise and retinal shadows within OCT B-scans occlude important edges, fine textures and deep tissues, preventing accurate and robust diagnosis by algorithms and clinicians. We developed a single process that successfully removed both noise and retinal shadows from unseen single-frame B-scans within 10.4ms. Mean average gradient magnitude (AGM) for the proposed algorithm was 57.2% higher than current state-of-the-art, while mean peak signal to noise ratio (PSNR), contrast to noise ratio (CNR), and structural similarity index metric (SSIM) increased by 11.1%, 154% and 187% respectively compared to single-frame B-scans. Mean intralayer contrast (ILC) improvement for the retinal ...

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    14. Utilisation of poor-quality optical coherence tomography scans: adjustment algorithm from the Singapore Epidemiology of Eye Diseases (SEED) study

      Utilisation of poor-quality optical coherence tomography scans: adjustment algorithm from the Singapore Epidemiology of Eye Diseases (SEED) study

      Purpose To evaluate the effect of signal strength (SS) on optical coherence tomography (OCT) parameters, and devise an algorithm to adjust the effect, when acceptable SS cannot be obtained. Methods 5085 individuals (9582 eyes), aged ≥40 years from the Singapore Epidemiology of Eye Diseases population-based study were included. Everyone underwent a standardised ocular examination and imaging with Cirrus HD-OCT. Effect of SS was evaluated using multiple structural breaks linear mixed-effect models. Expected change for increment in SS between 4 and 10 for individual parameter was calculated. Subsequently we devised and evaluated an algorithm to adjust OCT parameters to higher SS ...

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    15. Focal Structure-Function Relationships in Primary Open-Angle Glaucoma Using OCT and OCT-A Measurements

      Focal Structure-Function Relationships in Primary Open-Angle Glaucoma Using OCT and OCT-A Measurements

      Purpose: To evaluate the focal structure-function associations among visual field (VF) loss, optical coherence tomography angiography (OCT-A) vascular measurements, and optical coherence tomography (OCT) structural measurements in glaucoma. Methods: In this cross-sectional study, subjects underwent standard automated perimetry, OCT-based nerve fiber thickness measurements, and OCT-A imaging. Mappings of focal VF test locations with OCT and OCT-A measurements were defined using anatomically adjusted nerve fiber trajectories and were studied using multivariate mixed-effects analysis. Segmented regression analysis was used to determine the presence of breakpoints in the structure-function associations. Results: The study included 119 eyes from 86 Chinese subjects with primary open-angle ...

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    16. Longitudinal assessment of optic nerve head changes using optical coherence tomography in a primate microbead model of ocular hypertension

      Longitudinal assessment of optic nerve head changes using optical coherence tomography in a primate microbead model of ocular hypertension

      In humans, the longitudinal characterisation of early optic nerve head (ONH) damage in ocular hypertension (OHT) is difficult as patients with glaucoma usually have structural ONH damage at the time of diagnosis. Previous studies assessed glaucomatous ONH cupping by measuring the anterior lamina cribrosa depth (LCD) and minimal rim width (MRW) using optical coherence tomography (OCT). In this study, we induced OHT by repeated intracameral microbead injections in 16 cynomolgus primates (10 unilateral; 6 bilateral) and assessed the structural changes of the ONH longitudinally to observe early changes. Elevated intraocular pressure (IOP) in OHT eyes was maintained for 7 months ...

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    17. Effect of Pharmacological Pupil Dilatation on Angle Configuration in Untreated Primary Angle Closure Suspects: A Swept Source Anterior Segment Optical Coherence Tomography Study

      Effect of Pharmacological Pupil Dilatation on Angle Configuration in Untreated Primary Angle Closure Suspects: A Swept Source Anterior Segment Optical Coherence Tomography Study

      Precis: Angle closure worsens with pharmacological dilatation in about 50.0% of the subjects diagnosed as primary angle closure suspects. Purpose: To evaluate the changes in angle configuration with swept source anterior segment optical coherence tomography before and after pharmacological pupil dilatation in untreated primary angle closure suspects. Patients & Methods: 106 subjects over the age of 50 years and diagnosed as primary angle closure suspects were included in this cross-sectional cohort study.360-degree scans of the angles were captured using swept source optical coherence tomography (SS-1000, Tomey Corporation, Nagoya, Japan) before and 1 hour after pharmacological dilatation . The angle scans ...

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    18. 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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    19. 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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    20. 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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    21. Recent advances in anterior chamber angle imaging

      Recent advances in anterior chamber angle imaging

      Differentiating the two main forms of primary glaucoma (open-angle and closed-angle glaucoma) depends on the correct assessment of the anterior chamber angle (ACA). This assessment will determine the management plan and prognosis for the disease. The standard method of examining the angle has been, for many years, slit-lamp gonioscopy. This method, although clinically still useful, is less robust for patient follow up and clinical research, given its low reproducibility. Several imaging technologies have been developed in recent years to improve the evaluation of the ACA and overcome the shortcomings of gonioscopy. These recent advances include three-dimensional and 360° analysis by ...

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    22. 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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    23. 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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    24. Anterior Segment Optical Coherence Tomography Is there a Clinical Role in Management of Primary Angle Closure Disease?

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

      Primary angle-closure disease (PACD) covers a spectrum that includes primary angle-closure suspect (PACS), primary angle-closure (PAC), primary angle-closure glaucoma (PACG), as well as acute primary angle closure (APAC). Accumulating evidence suggests that the pathogenesis of PACD is complex, with multiple contributory factors including variations in the anatomical or biometric characteristics of the angle segment structures. Advances in anterior segment optical coherence tomography (ASOCT) 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 ASOCT in the diagnosis, mechanistic evaluation and as a predictor for ...

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