1. Articles from Marcus Ang

    1-24 of 33 1 2 »
    1. Anterior segment optical coherence tomography angiography for iris vasculature in pigmented eyes

      Anterior segment optical coherence tomography angiography for iris vasculature in pigmented eyes

      Purpose To compare anterior segment optical coherence tomography angiography (AS-OCTA) systems in delineating normal iris vessels and iris neovascularisation (NVI) in eyes with pigmented irides. Methods Prospective study from January 2019 to June 2019 of 10 consecutive patients with normal pigmented iris, had AS-OCTA scans with a described illumination technique, before using the same protocol in five eyes with NVI (clinical stages 1–3). All scans were sequentially performed using a spectral-domain OCTA (SD-OCTA), and a swept-source OCTA (SS-OCTA, Plex Elite 9000). Images were graded by two masked observers for visibility, artefacts and NVI characteristics. The main outcome measure was ...

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    2. Optical Coherence Tomography Angiography in Diabetes and Diabetic Retinopathy

      Optical Coherence Tomography Angiography in Diabetes and Diabetic Retinopathy

      Diabetic retinopathy (DR) is a common complication of diabetes mellitus that disrupts the retinal microvasculature and is a leading cause of vision loss globally. Recently, optical coherence tomography angiography (OCTA) has been developed to image the retinal microvasculature, by generating 3-dimensional images based on the motion contrast of circulating blood cells. OCTA offers numerous benefits over traditional fluorescein angiography in visualizing the retinal vasculature in that it is non-invasive and safer; while its depth-resolved ability makes it possible to visualize the finer capillaries of the retinal capillary plexuses and choriocapillaris. High-quality OCTA images have also enabled the visualization of features ...

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    3. Optical Coherence Tomography Angiography Imaging to monitor Anti-VEGF treatment of Corneal Vascularization in a Rabbit Mode

      Optical Coherence Tomography Angiography Imaging to monitor Anti-VEGF treatment of Corneal Vascularization in a Rabbit Mode

      Optical coherence tomography angiography (OCTA) is a well-established non-invasive retinal vascular imaging technique. It has been recently adapted to image the anterior segment and has shown good potential to image corneal vascularisation. The purpose of the study is to evaluate the usefulness of OCTA to monitor regression of corneal vessels following anti-VEGF (vascular endothelial growth factor) treatment using a previously established corneal vascularisation rabbit model. The regression of vessels following the treatment with aflibercept and ranibizumab anti-VEGFs using both topical instillation and sub-conjunctival injection was quantified using OCTA and compared with ICGA (indocyanine green angiography). Overall vessel density measurements using ...

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    4. Optical coherence tomography angiography in diabetic retinopathy: a review of current applications

      Optical coherence tomography angiography in diabetic retinopathy: a review of current applications

      Background Diabetic retinopathy (DR) is a leading cause of vision loss in adults. Currently, the standard imaging technique to monitor and prognosticate DR and diabetic maculopathy is dye-based angiography. With the introduction of optical coherence tomography angiography (OCTA), it may serve as a potential rapid, non-invasive imaging modality as an adjunct. Main text Recent studies on the role of OCTA in DR include the use of vascular parameters e.g., vessel density, intercapillary spacing, vessel diameter index, length of vessels based on skeletonised OCTA, the total length of vessels, vascular architecture and area of the foveal avascular zone. These quantitative ...

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    5. 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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    6. Impact of systemic vascular risk factors on the choriocapillaris using optical coherence tomography angiography in patients with systemic hypertension

      Impact of systemic vascular risk factors on the choriocapillaris using optical coherence tomography angiography in patients with systemic hypertension

      We investigated the characteristics of the choriocapillaris flow voids using optical coherence tomography angiography (OCTA) in 85 patients (164 eyes) with hypertension (mean ± SD age, 56 ± 11 years; 45% women; 20% poorly controlled BP; 16% diabetes) who are without ocular diseases and determined possible correlations with systemic vascular risk factors. Data on 24-hour ambulatory blood pressure (BP), serum creatinine, and urine microalbumin/creatinine ratio (MCR) were collected. Estimated glomerular filtration rate (eGFR) was calculated based on CKD-EPI Creatinine Equation. OCTA imaging (6 × 6 mm scans; AngioVue) with quantitative microvascular analysis of the choriocapillaris was performed. Linear regression was used to ...

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    7. Optical Coherence Tomography Angiography for Evaluation of Reperfusion following Pterygium Surgery

      Optical Coherence Tomography Angiography for Evaluation of Reperfusion following Pterygium Surgery

      Purpose To describe the use of optical coherence tomography angiography (OCTA) to quantitatively monitor the conjunctival graft revascularization after pterygium excision and conjunctival autograft (CAG) transplantation. Design Prospective, interventional case series. Methods Ten patients undergoing pterygium excision and femtosecond laser-assisted CAG transplantation were included. OCTA was performed at 1 week, 1 and 3 months postoperatively at the CAG transplantation site and harvested area. The vessel density at three different depths: conjunctival epithelium or CAG epithelium, conjunctival stroma or CAG stroma, and episclera, was evaluated and quantified. The revascularization rate was assessed and correlated with the postoperative CAG thickness. Results No ...

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    8. Optical coherence tomography angiography for the anterior segment

      Optical coherence tomography angiography for the anterior segment

      Optical coherence tomography angiography (OCTA) is a rapid and non-invasive technique for imaging vasculature in the eye. As OCTA can produce high-resolution cross-sectional images and allow depth-resolved analysis for accurate localization of pathology of interest, it has become a promising method for anterior segment imaging. Furthermore, OCTA offers a more patient-friendly alternative to the conventional invasive dye-based fluorescent angiography. However, conventional OCTA systems are typically designed and optimized for the posterior segment of the eye, and thus using OCTA for anterior segment imaging can present several difficulties and limitations. In this review, we summarized the recent developments and clinical applications ...

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    9. Vessel density and En-face segmentation of optical coherence tomography angiography to analyse corneal vascularisation in an animal model

      Vessel density and En-face segmentation of optical coherence tomography angiography to analyse corneal vascularisation in an animal model

      Background Optical coherence tomography angiography (OCTA) is a novel non-invasive angiography technology that has recently been extensively studied for its utility in anterior segment imaging. In this study, we compared a split-spectrum amplitude decorrelation angiography (SSADA) OCTA and an optical micro-angiography (OMAG SD) OCTA system to current angiographic technique, indocyanine green angiography (ICGA), to assess corneal vascularisation in an animal model. Methods We imaged 16 rabbits, (one eye per animal) with corneal vascularisation using SSADA OCTA (AngioVue; Optovue Inc., USA), OMAG OCTA (Angioscan; RS-3000 Nidek Co. Ltd., Japan) and ICGA in the same region of interest of the cornea at ...

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    10. Imaging in myopia: potential biomarkers, current challenges and future developments

      Imaging in myopia: potential biomarkers, current challenges and future developments

      Myopia is rapidly increasing in Asia and around the world, while it is recognised that complications from high myopia may cause significant visual impairment. Thus, imaging the myopic eye is important for the diagnosis of sight-threatening complications, monitoring of disease progression and evaluation of treatments. For example, recent advances in high-resolution imaging using optical coherence tomography may delineate early myopic macula pathology, optical coherence tomography angiography may aid early choroidal neovascularisation detection, while multimodal imaging is important for monitoring treatment response. However, imaging the eye with high myopia accurately has its challenges and limitations, which are important for clinicians to ...

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    11. Quantitative analysis of choriocapillaris in non-human primates using swept-source optical coherence tomography angiography (SS-OCTA)

      Quantitative analysis of choriocapillaris in non-human primates using swept-source optical coherence tomography angiography (SS-OCTA)

      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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    12. Future clinical applicability of optical coherence tomography angiography

      Future clinical applicability of optical coherence tomography angiography

      Optical coherence tomography angiography (OCT‐A) is an emerging technology that allows for the non‐invasive imaging of the ocular microvasculature. Despite the wealth of observations and numerous research studies illustrating the potential clinical uses of OCT‐A, this technique is currently rarely used in routine clinical settings. In this review, technical and clinical aspects of OCT‐A imaging are discussed, and the future clinical potential of OCT‐A is considered. An understanding of the basic principles and limitations of OCT‐A technology will better inform clinicians of its future potential in the diagnosis and management of ocular diseases.

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    13. 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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    14. Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model

      Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model

      Corneal neovascularization (CoNV) could be treated by novel anti-angiogenic therapies, though reliable and objective imaging tools to evaluate corneal vasculature and treatment efficacy is still lacking. Optical coherence tomography angiography (OCTA) –currently designed as a retinal vascular imaging system— has been recently adapted for anterior-segment and showed good potential for successful imaging of CoNV. However, further development requires an animal model where parameters can be studied more carefully with histological comparison. Our study evaluated the OCTA in suture-induced CoNV in a rabbit model compared to indocyanine green angiography (ICGA) and slit-lamp photography (SLP). Overall vessel density measurements from OCTA showed ...

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    15. Novel application of In Vivo Micro-Optical Coherence Tomography to assess Cornea scarring in an Animal Model

      Novel application of In Vivo Micro-Optical Coherence Tomography to assess Cornea scarring in an Animal Model

      This pilot study uses a micro-optical coherence tomography (micro-OCT) system with ~1 μm axial resolution specifically to image the cornea and corneal scars in vivo . We used an established murine corneal scar model by irregular phototherapeutic keratectomy in ten C57BL/6 mice, with serial imaging using the micro-OCT and compared to anterior segment (AS-OCT) (RTvue, Optovue, Fremont, CA) before and after scar induction. Main outcome was agreement between the AS-OCT and micro-OCT using Bland-Altman plots (95% limits of agreement, LoA).We analysed 10 control eyes and 10 eyes with corneal scars and found that there was good agreement between AS-OCT ...

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    16. Optical coherence tomography angiography: a review of current and future clinical applications

      Optical coherence tomography angiography: a review of current and future clinical applications

      Optical coherence tomography angiography is a non-invasive imaging technique that now allows for simultaneous in vivo imaging of the morphology as well as the vasculature in the eye. In this review, we provide an update on the existing clinical applications of optical coherence tomography angiography technology from the anterior to posterior segment of the eye. We also discuss the limitations of optical coherence tomography angiography technology, as well as the caveats to the interpretation of images. As current optical coherence tomography angiography systems are optimized for the retina, most studies have focused on interpreting images from conditions such as age ...

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    17. Comparison of anterior segment optical coherence tomography angiography systems for corneal vascularisation

      Comparison of anterior segment optical coherence tomography angiography systems for corneal vascularisation

      Aim To newly describe a spectral-domain (SD) optical coherence tomography angiography (OCTA) for the cornea and directly compare two OCTA system scans of the same eyes with corneal vascularisation. Methods Cross-sectional, observational, comparative case series. We performed sequential OCTA scans (10 eyes of 10 subjects with corneal vascularisation,4 scans each eye) repeated using split-spectrum amplitude decorrelation algorithm angiography system (SSADA, AngioVue; Optovue Inc, USA) and SD OCTA (Angioscan; Nidek Co. Ltd, Japan) in the same region of interest. We analysed all scan images for repeatability, image quality and vessel density measurements and compared OCTA systems. Results We obtained substantial ...

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    18. Optical coherence tomography angiography in acute non-arteritic anterior ischaemic optic neuropathy

      Optical coherence tomography angiography in acute non-arteritic anterior ischaemic optic neuropathy

      Purpose To characterise vascular changes in eyes with acute non-arteritic anterior ischaemic optic neuropathy (NAION), using optical coherence tomography angiography (OCT-A) imaging. Methods This hospital-based observational case-control study included included five patients with acute NAION (6 eyes), within 7 days after onset of symptoms and 19 age-matched healthy controls (19 eyes). OCT-A (RTVue XR 100; Optovue, Fremont, California, USA), covering a 4.5×4.5 mm scan area, was used to evaluate peripapillary blood flow in cases and controls. The flow densities at the retinal and choroidal level were measured using the split-spectrum amplitude-decorrelation angiography algorithm. Results The mean age ...

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    19. Serial optical coherence tomography angiography for corneal vascularization

      Serial optical coherence tomography angiography for corneal vascularization

      Purpose Recently, optical coherence tomography angiography (OCTA) has been used to successfully delineate vessels within the retina. This current study aims to assess corneal vascularization secondary to herpetic keratitis pre- and post-treatment using serial OCTA imaging adapted for the anterior segment. Methods All eyes were scanned using the split-spectrum amplitude decorrelation angiography (SSADA) algorithm on the AngioVue OCTA system (Optovue Inc. Fremont, CA, USA) with an anterior segment lens adapter. Multiple scans in the regions of interest (ROI) before and after treatment were analysed to assess change in corneal vascularization in response to each treatment modality. Results We analyzed a ...

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      Mentions: Optovue
    20. Swept Source Optical Coherence Tomography Angiography for Contact Lens-Related Corneal Vascularization

      Swept Source Optical Coherence Tomography Angiography for Contact Lens-Related Corneal Vascularization

      Purpose . To describe a novel technique of adapting a swept-source optical coherence tomography angiography (OCTA) to image corneal vascularization. Methods . In this pilot cross-sectional study, we obtained 3 × 3 mm scans, where 100,000 A-scans are acquired per second with optical axial resolution of 8  μ m and lateral resolution of 20  μ m. This was performed with manual “XYZ” focus without the anterior segment lens, until the focus of the corneoscleral surface was clearly seen and the vessels of interest were in focus on the corresponding red-free image. En face scans were evaluated based on image quality score and repeatability. Results ...

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    21. Enhancement of Corneal Visibility in Optical Coherence Tomography Images with Corneal Opacification

      Enhancement of Corneal Visibility in Optical Coherence Tomography Images with Corneal Opacification

      Purpose : To establish and to rank the performance of a corneal adaptive compensation (CAC) algorithm in enhancing corneal images with scars acquired from three commercially available anterior segment optical coherence tomography (ASOCT) devices. Methods : Horizontal B-scans of the cornea were acquired from 10 patients using three ASOCT devices (Spectralis, RTVue, and Cirrus). We compared ASOCT image quality (with and without CAC) by computing the intralayer contrast (a measure of shadow removal), the interlayer contrast (a measure of tissue boundary visibility), and the tissue/background contrast (a measure of overall corneal visibility). All six groups (Spectralis, RTVue, Cirrus, Spectralis+CAC, RTVue ...

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    22. 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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    23. Optical coherence tomography angiography in dural carotid-cavernous sinus fistula

      Optical coherence tomography angiography in dural carotid-cavernous sinus fistula

      Background Recently, applications of optical coherence tomography angiography (OCTA) have been limited to the retina and posterior segment. Although early studies have described its use for other clinical applications, its role in anterior segment vasculature and optic disc imaging has been limited thus far. Case presentation We describe a novel clinical application of OCTA in a patient with dural carotid-cavernous sinus fistula (CCF), which was complicated by increased intra-ocular pressure (IOP). In this case report, we used the OCTA to delineate increased epsicleral venous flow in the affected eye with secondary raised IOP. Current measurements of episcleral venous pressure are ...

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    24. Optical coherence tomography angiography and indocyanine green angiography for corneal vascularisation

      Optical coherence tomography angiography and indocyanine green angiography for corneal vascularisation

      Background/Aim To describe an optical coherence tomography angiography (OCTA) system adapted for anterior segment imaging, compared with indocyanine green angiography (ICGA) in eyes with corneal vascularisation. Methods Retrospective study of subjects with corneal vascularisation secondary to microbial keratitis who had OCTA scans performed using a commercially available split-spectrum amplitude-decorrelation algorithm angiography system (AngioVue; Optovue Inc., Fremont, California, USA) and ICGA images (Spectralis; Heidelberg Engineering, Heidelberg, Germany). The agreement between OCTA and ICGA techniques in terms of area of vascularisation measured, using Bland–Altman 95% limits of agreement (LOA). Results We compared the area of corneal vascularisation in 64 scan ...

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    1-24 of 33 1 2 »
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    Quantitative Assessment of Changes in Trabeculectomy Blebs After Laser Suture Lysis Using Anterior Segment Coherence Tomography Anterior Segment Optical Tomography Study of the Cornea and Anterior Segment in Adult Ethnic South Asian Indian Eyes Comparison of Anterior Segment Optical Tomography Parameters Measured Using a Semi-Automatic Software to Standard Clinical Instruments Intraoperative Anterior Segment Optical Coherence Tomography: A Novel Assessment Tool during Deep Anterior Lamellar Keratoplasty Pretreatment Anterior Segment Imaging During Acute Primary Angle Closure: Insights into Angle Closure Mechanisms in the Acute Phase Descemet Membrane Endothelial Keratoplasty: Intraoperative and Postoperative Imaging Spectral-Domain Optical Coherence Tomography Enhancement of Corneal Visibility in Optical Coherence Tomography Images Using Corneal Adaptive Compensation Optical Coherence Tomography Angiography for Anterior Segment Vasculature Imaging Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model Optical coherence tomography angiography in acute non-arteritic anterior ischaemic optic neuropathy Long-Term Arterial Remodeling After Bioresorbable Scaffold Implantation 4-Year Follow-up of Quantitative Coronary Angiography, Histology and Optical Coherence Tomography Visualization of Bacterial Colonization and Cellular Layers in a Gut-on-a-Chip System Using Optical Coherence Tomography