1. Articles from Hla M. Htoon

    1-12 of 12
    1. Optical coherence tomography angiography for the assessment of choroidal vasculature in high myopia

      Optical coherence tomography angiography for the assessment of choroidal vasculature in high myopia

      Aims To assess specific layers of the choroid in highly myopic young adults and to examine their associations with levels of myopia. Methods We recruited 51 young myopes (n=91 eyes) from the Singapore Cohort of Risk Factors for Myopia cohort. We performed standardised optical coherence tomography (OCT) and OCT angiography imaging and developed a novel segmentation technique assessing choroidal layers’ thickness (overall choroidal thickness (CT), medium-vessel choroidal layer (MVCL) thickness, large-vessel choroidal layer (LVCL)) and vasculature (choroidal vessel density (%), choroidal branch area (CBA, %) and mean choroidal vessel width (MCVW, mm)). Results We found that eyes with extreme myopia (EM ...

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    2. Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

      Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

      Recent developments in optical coherence tomography (OCT) systems for the cornea have limited resolution or acquisition speed. In this study we aim to evaluate the use of a ‘micro-OCT’ (μOCT ~1 μm axial resolution) compared to existing imaging modalities using animal models of corneal endothelial disease. We used established cryoinjury and bullous keratopathy models in Sprague Dawley rats comparing ex vivo μOCT imaging in normal and diseased eyes to (1) histology; (2) in vivo confocal microscopy (IVCM); and (3) scanning electron microscopy (SEM). Qualitative and quantitative comparisons amongst imaging modalities were performed using mean endothelial cell circularity [(4π × Area)/Perimeter ...

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    3. 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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    4. 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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    5. 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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    6. Reproducibility and age-related changes of ocular parametric measurements in rabbits

      Reproducibility and age-related changes of ocular parametric measurements in rabbits

      Background The rabbit is a common animal model for ophthalmic research, especially corneal research. Ocular structures grow rapidly during the early stages of life. It is unclear when the rabbit cornea becomes mature and stabilized. We investigated the changes of keratometry, refractive state and central corneal thickness (CCT) with age. In addition, we studied the intra- and inter-observer reproducibility of anterior chamber depth (ACD) and anterior chamber width (ACW) measurements in rabbits using anterior segment-optical coherence tomography (AS-OCT). Results The growth of New Zealand White rabbits (n = 16) were monitored from age 1 to 12 months old. Corneal keratometric and ...

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    7. 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

      Purpose. To compare two spectral domain optical coherence tomography (SD-OCT) devices for the identification of angle structures and the presence of angle closure. Methods. This was a prospective comparative study. Consecutive patients underwent gonioscopy and anterior segment imaging using two SD-OCT devices (iVue and Cirrus). Images were evaluated for the ability to detect angle structures such as Schwalbe's line (SL), trabecular meshwork (TM), Schlemm's canal (SC), and scleral spur (SS), and the presence of angle closure. Angle closure was defined as iris contact with the angle wall anterior to the SS on SD-OCT, and nonvisibility of the posterior ...

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    8. 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

      Purpose. To compare two spectral domain optical coherence tomography (SD-OCT) devices for the identification of angle structures and the presence of angle closure Methods. This was a prospective comparative study. Consecutive patients underwent gonioscopy and anterior segment imaging using 2 SD-OCT devices (iVue [Optovue Corporation, Fremont, Ca] and Cirrus [Carl Zeiss Meditec, Dublin, Ca]). Images were evaluated for the ability to detect angle structures such as Schwalbe's line (SL), trabecular meshwork (TM), Schlemm's canal (SC), and scleral spur (SS); and the presence of angle closure. Angle closure was defined as iris contact with the angle wall anterior to ...

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    9. Reproducibility of Cornea Measurements in Anterior Segment OCT images of Normal Eyes and Eyes with Bullous Keratopathy Analyzed with the Zhongshan Assessment Program (ZAP)

      Reproducibility of Cornea Measurements in Anterior Segment OCT images of Normal Eyes and Eyes with Bullous Keratopathy Analyzed with the Zhongshan Assessment Program (ZAP)

      Purpose: To determine the interobserver and intraobserver measurement reproducibility of cornea parameters of both normal eyes and eyes with bullous keratopathy obtained with the Zhongshan Assessment Program (ZAP, Guangzhou, China) on Anterior segment optical coherence tomography (AS-OCT, Visante; Carl Zeiss Meditec, Dublin, CA) images. Methods: Comparative study of 24 healthy volunteers and 25 subjects with bullous keratopathy (BK). AS-OCT images were independently analyzed by two examiners. Parameters examined: anterior chamber depth (ACD), central corneal thickness (CCT), posterior corneal curvature (PCC) and posterior corneal arc length (PCAL). Interobserver and intraobserver reproducibility of the above parameters was calculated in terms of limits ...

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    10. Laser in situ keratomileusis flap measurements: Comparison between observers and between spectral-domain and time-domain anterior segment optical coherence tomography

      Laser in situ keratomileusis flap measurements: Comparison between observers and between spectral-domain and time-domain anterior segment optical coherence tomography

      Purpose To evaluate the between-observer (interobserver) and between-instrument (intraobserver) variability in flap thickness measurements after laser in situ keratomileusis (LASIK) using spectral-domain and time-domain anterior segment optical coherence tomography (AS-OCT). Setting Singapore National Eye Centre. Design Evaluation of diagnostic test or technology. Methods Two independent masked observers measured flap thickness 1 month after LASIK using spectral-domain (RTVue) or time-domain (Visante) AS-OCT. The measurements were taken at central (0.0 mm), −1.5 mm, and +1.5 mm locations. Measurements were repeated to assess between-instrument variability. Results There was no statistically significant difference in mean flap thickness between the 2 observers ...

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    11. Biometry of the Cornea and Anterior Chamber in Chinese Eyes: an Anterior Segment Optical Coherence Tomography Study

      Purpose: To investigate the normative data of corneal and anterior segment biometric parameters in Chinese adults and their associations for use in preoperative assessment for corneal and anterior segment surgery. Methods: This cross-sectional, population based study included 750 subjects aged 50 years. The subjects underwent an ophthalmic examination including imaging using anterior segment optical coherence tomography (AS-OCT). Dimensions were subsequently measured with the Zhongshan Assessment Program (ZAP). We also include posterior corneal arc length (PCAL), a novel parameter defined as the arc distance between scleral spurs on the posterior border of the cornea. Correlations with age, gender, height, weight, body ...

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    12. Variation of Angle Parameters in Asians: An Anterior Segment Optical Coherence Tomography Study in a Population of Singapore Malays

      Objective: To assess variations in angle parameters using anterior segment optical coherence tomography (AS-OCT) and to investigate demographic, ocular and systemic associations of angle width. Methods: This was a sub-study of a population based, cross-sectional survey of 3,280 (78.7% response rate) Malay people aged 40-80 years in Singapore. All participants underwent a standardized interview and ocular and systemic examination. AS-OCT was performed on 291 consecutive patients under standardized dark conditions. Angle opening distance (AOD-500) and trabecular-iris space area (TISA-500) 500 um from the scleral spur were determined for the nasal and temporal angles. Anterior chamber depth (ACD) was ...

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    1-12 of 12
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    1. (11 articles) Singapore Eye Research Institute
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    Laser in situ keratomileusis flap measurements: Comparison between observers and between spectral-domain and time-domain anterior segment optical coherence tomography Reproducibility of Cornea Measurements in Anterior Segment OCT images of Normal Eyes and Eyes with Bullous Keratopathy Analyzed with the Zhongshan Assessment Program (ZAP) 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 Reproducibility and age-related changes of ocular parametric measurements in rabbits Sectoral variations of iridocorneal angle width and iris volume in Chinese Singaporeans: a swept-source optical coherence tomography study Determinants of Optical Coherence Tomography–Derived Minimum Neuroretinal Rim Width in a Normal Chinese Population Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model Evaluating Retinal and Choroidal Perfusion Changes After Ocular Massage of Healthy Eyes Using Optical Coherence Tomography Angiography Dermal Epidermal Junction Detection for Full-Field Optical Coherence Tomography Data of Human Skin by Deep Learning OctNET: A Lightweight CNN for Retinal Disease Classification from Optical Coherence Tomography Images The Association between Tear Film Thickness as Measured with OCT and Symptoms and Signs of Dry Eye Disease: A Pooled Analysis of 6 Clinical Trials