1. Articles from paul t. k. chew

    1-8 of 8
    1. Complex wavelet based quality assessment for AS-OCT images with application to Angle Closure Glaucoma diagnosis

      Complex wavelet based quality assessment for AS-OCT images with application to Angle Closure Glaucoma diagnosis

      Background and objectives Angle closure disease in the eye can be detected using time-domain Anterior Segment Optical Coherence Tomography (AS-OCT). The Anterior Chamber (AC) characteristics can be quantified from AS-OCT image, which is dependent on the image quality at the image acquisition stage. To date, to the best of our knowledge there are no objective or automated subjective measurements to assess the quality of AS-OCT images. Methods To address AS-OCT image quality assessment issue, we define a method for objective assessment of AS-OCT images using complex wavelet based local binary pattern features. These features are pooled using the Naïve ...

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    2. Automated anterior segment OCT image analysis for Angle Closure Glaucoma mechanisms classification

      Automated anterior segment OCT image analysis for Angle Closure Glaucoma mechanisms classification

      Background and objectives Angle closure glaucoma (ACG) is an eye disease prevalent throughout the world. ACG is caused by four major mechanisms: exaggerated lens vault, pupil block, thick peripheral iris roll, and plateau iris. Identifying the specific mechanism in a given patient is important because each mechanism requires a specific medication and treatment regimen. Traditional methods of classifying these four mechanisms are based on clinically important parameters measured from anterior segment optical coherence tomography (AS-OCT) images, which rely on accurate segmentation of the AS-OCT image and identification of the scleral spur in the segmented AS-OCT images by clinicians. Methods In ...

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    3. Pretreatment Anterior Segment Imaging During Acute Primary Angle Closure: Insights into Angle Closure Mechanisms in the Acute Phase

      Pretreatment Anterior Segment Imaging During Acute Primary Angle Closure: Insights into Angle Closure Mechanisms in the Acute Phase

      Objective To describe anterior segment optical coherence tomography (ASOCT) parameters during acute primary angle closure (APAC) before therapeutic interventions and comparative analyses of biometric parameters of APAC eyes with fellow eyes. Design Prospective, comparative case series. Participants Thirty-one consecutive patients with APAC. Methods All patients underwent ASOCT imaging of both eyes during the attack, before therapeutic interventions were administered. Custom software was used to measure anterior chamber depth (ACD), anterior chamber area (ACA), anterior chamber volume (ACV), iris curvature (I-Curv), iris area (I-Area), lens vault (LV), and angle opening distance (AOD750), trabecular iris space area (TISA750), and iris thickness (IT750 ...

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    4. Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms

      Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms

      Background:  To evaluate different mechanisms of primary angle closure (PAC) and to quantify anterior chamber (AC) parameters in these mechanisms using anterior segment optical coherence tomography (AS-OCT) in an Asian population. Design:  Hospital based cross sectional observational study. Participants:  Forty-eight consecutive patients with PAC and PAC glaucoma. Methods:   Patients underwent complete ophthalmic examination and imaging of nasal-temporal angles with AS-OCT. Images were categorized into 4 PAC mechanisms: pupil block (PB), plateau (PL) iris configuration, Thick peripheral iris roll (PIR) and exaggerated lens vault (LV). Parameters computed: AC depth central (ACDC), ACD1000 and ACD2000 (ACD at 1000µm and 2000µm anterior to ...

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    5. Changes in Anterior Segment Morphology after Laser Peripheral Iridotomy: An Anterior Segment Optical Coherence Tomography Study

      Changes in Anterior Segment Morphology after Laser Peripheral Iridotomy: An Anterior Segment Optical Coherence Tomography Study

      Purpose Novel anterior segment optical coherence tomography (ASOCT) parameters associated with angle closure include anterior chamber area (ACA), anterior chamber volume (ACV), anterior chamber width (ACW), lens vault (LV), iris thickness (IT), iris area (I-area), and iris curvature (I-curv). We aimed to investigate changes in these parameters after laser peripheral iridotomy (LPI) in a cohort of primary angle-closure suspects (PACS). Design Prospective observational study. Participants and Controls A total of 176 PACS aged ≥50 years who underwent LPI in 1 eye. Methods We analyzed ASOCT images (Visante, Carl Zeiss Meditec, Dublin, CA) from all subjects using customized software before and ...

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    6. High-definition imaging of trabeculectomy blebs using spectral domain optical coherence tomography adapted for the anterior segment

      Background: The aim of this work was to image trabeculectomy blebs using spectral domain optical coherence tomography (SDOCT).Methods: In this prospective cross-sectional study, patients who had undergone trabeculectomy with at least 3 months of follow up were included. Blebs were imaged using an adapted SDOCT system (Cirrus HD-OCT, Carl Zeiss Meditec Inc., Dublin, CA, USA) and time domain anterior segment optical coherence tomography (ASOCT) (Visante OCT, Carl Zeiss Meditec Inc.). An observer masked to clinical data assessed the utility of SDOCT and ASOCT in visualizing structures in successful and failed blebs.Results: Fifty-one eyes were imaged, of which 43 ...
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    7. Changes in Angle Configuration After Phacoemulsification Measured by Anterior Segment Optical Coherence Tomography.

      Purpose: To measure changes in angle width after phacoemulsification and intraocular lens (IOL) implantation using anterior segment optical coherence tomography (AS-OCT). Materials and Methods: Twenty-one patients undergoing cataract surgery were recruited from the National University Hospital, Singapore. AS-OCT images were obtained of nasal and temporal angle quadrants before and at 1-month after surgery. Optical measurements of central anterior chamber depth were obtained, and gonioscopic measurement of angle width was recorded. AS-OCT angle width parameters measured in the nasal and temporal quadrants included the angle opening distance at 500 [mu]m (AOD500) anterior to the scleral spur and the trabecular iris ...

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    8. Changes in anterior segment morphology in response to illumination and after laser iridotomy in Asian eyes: an anterior segment OCT study

      Aim: Using the anterior segment optical coherence tomography (AS-OCT) to quantify changes in anterior segment morphology going from light to dark and following laser iridotomy (LI). Methods: Prospective observational study. 17 consecutive subjects without peripheral anterior synechiae undergoing LI were evaluated using gonioscopy and AS-OCT. Angle configuration including angle opening distance (AOD) at 500 microns anterior to the scleral spur, AOD500, trabecular-iris space area up to 750 microns from the scleral spur, TISA750 and the increase in angle opening going from dark to light conditions was determined. Results: Both mean AOD500 and TISA750 increased nearly threefold going from dark to ...

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    1-8 of 8
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    1. (7 articles) National University of Singapore
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    Changes in Anterior Segment Morphology after Laser Peripheral Iridotomy: An Anterior Segment Optical Coherence Tomography Study Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms Pretreatment Anterior Segment Imaging During Acute Primary Angle Closure: Insights into Angle Closure Mechanisms in the Acute Phase Automated anterior segment OCT image analysis for Angle Closure Glaucoma mechanisms classification Complex wavelet based quality assessment for AS-OCT images with application to Angle Closure Glaucoma diagnosis A Deep Learning Framework for the Detection and Quantification of Reticular Pseudodrusen and Drusen on Optical Coherence Tomography Quantitative assessment of textural features in the early detection of diabetic retinopathy with optical coherence tomography angiography Line-field confocal optical coherence tomography of fibroepithelioma of Pinkus Assessment of demineralized tooth lesions using optical coherence tomography and other state-of-the-art technologies: a review Optic disc and retinal vessel densities assessment by optical coherence tomography angiography in patients with keratoconus Optical coherence tomography angiography in Bietti crystalline dystrophy Choroidal vascularity profile in diabetic eyes using wide field optical coherence tomography