1. Articles from Leopold Schmetterer

    1-24 of 93 1 2 3 4 »
    1. Evaluation of Generative Adversarial Networks for High-Resolution Synthetic Image Generation of Circumpapillary Optical Coherence Tomography Images for Glaucoma

      Evaluation of Generative Adversarial Networks for High-Resolution Synthetic Image Generation of Circumpapillary Optical Coherence Tomography Images for Glaucoma

      Importance: Deep learning (DL) networks require large data sets for training, which can be challenging to collect clinically. Generative models could be used to generate large numbers of synthetic optical coherence tomography (OCT) images to train such DL networks for glaucoma detection. Objective: To assess whether generative models can synthesize circumpapillary optic nerve head OCT images of normal and glaucomatous eyes and determine the usability of synthetic images for training DL models for glaucoma detection. Design, setting, and participants: Progressively growing generative adversarial network models were trained to generate circumpapillary OCT scans. Image gradeability and authenticity were evaluated on a ...

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    2. Normative data and associations of Optical Coherence Tomography Angiography measurements of the macula: The Singapore Malay Eye Study

      Normative data and associations of Optical Coherence Tomography Angiography measurements of the macula: The Singapore Malay Eye Study

      Objective: To describe the normative quantitative parameters of macular retinal vasculature and their systemic and ocular associations, using optical coherence tomography angiography (OCTA). Design: Population based cross sectional study SUBJECTS: Adults above 50 years old were recruited from the third examination of the population-based Singapore Malay Eye Study. Methods: All participants underwent standardized comprehensive examination and Spectral domain-OCTA (Optovue, USA) of the macula. OCTA scans with pre-existing retinal disease, macular pathology, and poor quality were excluded. Main outcome measures: Normative quantitative vessel densities of the superficial, deep layer and foveal avascular zone were evaluated. Ocular and systemic associations with macular ...

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    3. The New Era of Retinal Imaging in Hypertensive Patients

      The New Era of Retinal Imaging in Hypertensive Patients

      Structural and functional alterations in the microcirculation by systemic hypertension can cause significant organ damage at the eye, heart, brain, and kidneys. As the retina is the only tissue in the body that allows direct imaging of small vessels, the relationship of hypertensive retinopathy signs with development of disease states in other organs have been extensively studied; large-scale epidemiological studies using fundus photography and advanced semi-automated analysis software have reported the association of retinopathy signs with hypertensive end-organ damage includes the following: stroke, dementia, and coronary heart disease. Although yielding much useful information, the vessels assessed from fundus photographs remain ...

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    4. A multi-regression approach to improve optical coherence tomography diagnostic accuracy in multiple sclerosis patients without previous optic neuritis

      A multi-regression approach to improve optical coherence tomography diagnostic accuracy in multiple sclerosis patients without previous optic neuritis

      Background: Optical coherence tomography (OCT) is a retinal imaging system that may improve the diagnosis of multiple sclerosis (MS) persons, but the evidence is currently equivocal. To assess whether compensating the peripapillary retinal nerve fiber layer (pRNFL) thickness for ocular anatomical features as well as the combination with macular layers can improve the capability of OCT in differentiating non-optic neuritis eyes of relapsing-remitting MS patients from healthy controls. Methods: 74 MS participants (n = 129 eyes) and 84 age- and sex-matched healthy controls (n = 149 eyes) were enrolled. Macular ganglion cell complex (mGCC) thickness was extracted and pRNFL measurement was compensated ...

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    5. Anterior Segment Optical Coherence Tomography Angiography Following Trabecular Bypass Minimally Invasive Glaucoma Surgery

      Anterior Segment Optical Coherence Tomography Angiography Following Trabecular Bypass Minimally Invasive Glaucoma Surgery

      Objective: To assess anterior segment optical coherence tomography angiography (AS-OCTA) imaging of the episcleral vessels before and after trabecular bypass minimally invasive glaucoma surgery (MIGS). Design: A prospective, clinical, single-centre, single-arm pilot feasibility study conducted at National University Hospital, Singapore. Subjects: Patients with primary glaucomatous optic neuropathy undergoing Hydrus Microstent (Ivantis Inc., Irvine, CA, USA) implantation, who require at least one intra-ocular pressure-lowering medication. One or two eyes per patient may be enrolled. Methods: We performed AS-OCTA (Nidek RS-3000 Advance 2, Gamagori, Japan) pre- and up to 6 months post-MIGS implantation using a standard protocol in all cornealimbal quadrants, to ...

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    6. A multi-regression framework to improve diagnostic ability of optical coherence tomography retinal biomarkers to discriminate mild cognitive impairment and Alzheimer’s disease

      A multi-regression framework to improve diagnostic ability of optical coherence tomography retinal biomarkers to discriminate mild cognitive impairment and Alzheimer’s disease

      Background: Diagnostic performance of optical coherence tomography (OCT) to detect Alzheimer's disease (AD) and mild cognitive impairment (MCI) remains limited. We assessed whether compensating the circumpapillary retinal nerve fiber layer (cpRNFL) thickness for multiple demographic and anatomical factors as well as the combination of macular layers improves the detection of MCI and AD. Methods: This cross-sectional study of 62 AD (n = 92 eyes), 108 MCI (n = 158 eyes), and 55 cognitively normal control (n = 86 eyes) participants. Macular ganglion cell complex (mGCC) thickness was extracted. Circumpapillary retinal nerve fiber layer (cpRNFL) measurement was compensated for several ocular factors. Thickness ...

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    7. Outcome Measures for Disease Monitoring in Intraocular Inflammatory and Infectious Diseases (OCTOMERIA): Understanding the Choroid in Uveitis with Optical Coherence Tomography (OCT)

      Outcome Measures for Disease Monitoring in Intraocular Inflammatory and Infectious Diseases (OCTOMERIA): Understanding the Choroid in Uveitis with Optical Coherence Tomography (OCT)

      Purpose: To compare imaging modalities for the choroid of the eye, and evaluate various choroidal changes in uveitides entities. Methods: A comprehensive systematic literature review was conducted looking at current imaging modalities available to assess choroid architecture and commonly used parameters available to qualify and quantify choroidal changes, before looking at specific uveitides entities with choroidal involvement which have been broadly separated into non-infectious and infectious in etiology. Results: We describe the various modalities currently available to evaluate the choroid of the eye such as Ultrasound B Scan, ICGA, and OCT. Choroidal changes in various ocular and systemic diseases such ...

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    8. Combining retinal and choroidal microvascular metrics improves discriminative power for diabetic retinopathy

      Combining retinal and choroidal microvascular metrics improves discriminative power for diabetic retinopathy

      Purpose To use optical coherence tomography angiography (OCTA) parameters from both the retinal and choroidal microvasculature to detect the presence and severity of diabetic retinopathy (DR). Method This is a cross-sectional case–control study. OCTA parameters from retinal vasculature, fovea avascular zone (FAZ) and choriocapillaris were evaluated from 3×3 mm 2 fovea-centred scans. Areas under the receiver operating characteristic (ROC) curve were used to compare the discriminative power on the presence of diabetes mellitus (DM), the presence of DR and need for referral: group 1 (no DM vs DM no DR), group 2 (no DR vs any DR) and ...

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    9. Multi-task learning approach for volumetric segmentation and reconstruction in 3D OCT images

      Multi-task learning approach for volumetric segmentation and reconstruction in 3D OCT images

      The choroid is the vascular layer of the eye that supplies photoreceptors with oxygen. Changes in the choroid are associated with many pathologies including myopia where the choroid progressively thins due to axial elongation. To quantize these changes, there is a need to automatically and accurately segment the choroidal layer from optical coherence tomography (OCT) images. In this paper, we propose a multi-task learning approach to segment the choroid from three-dimensional OCT images. Our proposed architecture aggregates the spatial context from adjacent cross-sectional slices to reconstruct the central slice. Spatial context learned by this reconstruction mechanism is then fused with ...

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    10. Quantification of intrinsic optical signals in the outer human retina using optical coherence tomography

      Quantification of intrinsic optical signals in the outer human retina using optical coherence tomography

      Intrinsic optical signals constitute a noninvasive biomarker promising the objective assessment of retinal photoreceptor function. We employed a commercial optical coherence tomography (OCT) system and an OCT signal model for evaluation of optical path length (OPL) changes in the temporal outer retina of five healthy subjects during light adaptation. Data were acquired at 30 time points, in ambient light and during long duration stimulation with white light, and analyzed, employing a signal model based on the sum of seven Gaussian curves corresponding to all relevant anatomical structures of the outer retina. During light stimulation, mean OPL between rod outer segment ...

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    11. Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography

      Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography

      Purpose: To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer. Methods: Twenty-four healthy volunteers participated in this randomized, double-masked, cross-over study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusion density was calculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of ...

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    12. 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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    13. The Application of Optical Coherence Tomography Angiography in Systemic Hypertension: A Meta-Analysis

      The Application of Optical Coherence Tomography Angiography in Systemic Hypertension: A Meta-Analysis

      Objective: Multiple studies have compared various optical coherence tomography angiography (OCTA) parameters in participants with systemic hypertension vs. controls and have presented discordant findings. We conducted a meta-analysis to pool together data from different studies to generate an overall effect size and find out whether OCTA parameter(s) significantly differed in participants with systemic hypertension as compared to controls. Methods: We conducted a literature search through a search of electronic databases to identify studies before 19 June 2021, which compared OCTA parameters in non-diabetic participants with systemic hypertension vs. controls. If the OCTA parameter had a minimum number of 3 ...

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    14. Ultrawide field, distortion-corrected ocular shape estimation with MHz optical coherence tomography (OCT)

      Ultrawide field, distortion-corrected ocular shape estimation with MHz optical coherence tomography (OCT)

      Ocular deformation may be associated with biomechanical alterations in the structures of the eye, especially the cornea and sclera in conditions such as keratoconus, congenital glaucoma, and pathological myopia. Here, we propose a method to estimate ocular shape using an ultra-wide field MHz swept-source optical coherence tomography (SS-OCT) with a Fourier Domain Mode-Locked (FDML) laser and distortion correction of the images. The ocular biometrics for distortion correction was collected by an IOLMaster 700, and localized Gaussian curvature was proposed to quantify the ocular curvature covering a field-of-view up to 65°×62°. We achieved repeatable curvature shape measurements (intraclass coefficient = 0 ...

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    15. Role of anterior segment optical coherence tomography angiography in the assessment of acute chemical ocular injury: a pilot animal model study

      Role of anterior segment optical coherence tomography angiography in the assessment of acute chemical ocular injury: a pilot animal model study

      To examine the use of anterior segment-optical coherence tomography angiography (AS-OCTA) in the assessment of limbal ischemia in an animal model chemical ocular injury. We conducted a prospective study using an established chemical ocular injury model in 6 rabbits (12 eyes), dividing the cornea limbus into 4 quadrants. Chemical injury grade was induced based on extent of limbal injury (0 to 360 degrees) and all eyes underwent serial slit-lamp with AS-OCTA imaging up to one month. Main outcome measure was changes in AS-OCTA vessel density (VD) comparing injured and control cornea limbal quadrants within 24 h and at one month ...

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    16. Developing a normative database for retinal perfusion using optical coherence tomography angiography

      Developing a normative database for retinal perfusion using optical coherence tomography angiography

      Visualizing and characterizing microvascular abnormalities with optical coherence tomography angiography (OCTA) has deepened our understanding of ocular diseases, such as glaucoma, diabetic retinopathy, and age-related macular degeneration. Two types of microvascular defects can be detected by OCTA: focal decrease because of localized absence and collapse of retinal capillaries, which is referred to as the non-perfusion area in OCTA, and diffuse perfusion decrease usually detected by comparing with healthy case-control groups. Wider OCTA allows for insights into peripheral retinal vascularity, but the heterogeneous perfusion distribution from the macula, parapapillary area to periphery hurdles the quantitative assessment. A normative database for OCTA ...

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    17. Framework for quantitative three-dimensional choroidal vasculature analysis using optical coherence tomography

      Framework for quantitative three-dimensional choroidal vasculature analysis using optical coherence tomography

      Choroidal vasculature plays an important role in the pathogenesis of retinal diseases, such as myopic maculopathy, age-related macular degeneration, diabetic retinopathy, central serous chorioretinopathy, and ocular inflammatory diseases. Current optical coherence tomography (OCT) technology provides three-dimensional visualization of the choroidal angioarchitecture; however, quantitative measures remain challenging. Here, we propose and validate a framework to segment and quantify the choroidal vasculature from a prototype swept-source OCT (PLEX Elite 9000, Carl Zeiss Meditec, USA) using a 3×3 mm scan protocol centered on the macula. Enface images referenced from the retinal pigment epithelium were reconstructed from the volumetric data. The boundaries of ...

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    18. Anterior Segment Optical Coherence Tomography Angiography Assessment of Corneal Vascularisation After Combined Fine-Needle Diathermy with Subconjunctival Ranibizumab: A Pilot Study

      Anterior Segment Optical Coherence Tomography Angiography Assessment of Corneal Vascularisation After Combined Fine-Needle Diathermy with Subconjunctival Ranibizumab: A Pilot Study

      Introduction: To describe anterior segment optical coherence tomography angiography (AS-OCTA) imaging to monitor corneal vascularisation (CoNV) and scar reduction after combined fine-needle diathermy (FND) with subconjunctival ranibizumab. Methods: Prospective clinical study of six eyes from six subjects with corneal scar and CoNV which underwent combined FND with subconjunctival ranibizumab. All eyes were imaged using slit-lamp photography (SLP) and AS-OCTA (Optovue, Inc., Fremont, CA, wavelength: 840 nm) before and after the operation, with two independent masked assessors analysing all images. Main outcome measures were changes in median corneal scar area and vessel density (AS-OCTA) comparing pre- and postoperative imaging up to ...

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    19. Segregation of neuronal-vascular components in a retinal nerve fiber layer for thickness measurement using OCT and OCT angiography

      Segregation of neuronal-vascular components in a retinal nerve fiber layer for thickness measurement using OCT and OCT angiography

      Assessment of the circumpapillary retinal nerve fiber layer (RNFL) provides crucial knowledge on the status of the optic nerve. Current circumpapillary RNFL measurements consider only thickness, but an accurate evaluation should also consider blood vessel contribution. Previous studies considered the presence of major vessels in RNFL thickness measurements from optical coherence tomography (OCT). However, such quantitative measurements do not account for smaller vessels, which could also affect circumpapillary RNFL measurements. We present an approach to automatically segregate the neuronal and vascular components in circumpapillary RNFL by combining vascular information from OCT angiography (OCTA) and structural data from OCT. Automated segmentation ...

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    20. Towards ‘automated gonioscopy’: a deep learning algorithm for 360° angle assessment by swept-source optical coherence tomography

      Towards ‘automated gonioscopy’: a deep learning algorithm for 360° angle assessment by swept-source optical coherence tomography

      Aims: To validate a deep learning (DL) algorithm (DLA) for 360° angle assessment on swept-source optical coherence tomography (SS-OCT) (CASIA SS-1000, Tomey Corporation, Nagoya, Japan). Methods: This was a reliability analysis from a cross-sectional study. An independent test set of 39 936 SS-OCT scans from 312 phakic subjects (128 SS-OCT meridional scans per eye) was analysed. Participants above 50 years with no previous history of intraocular surgery were consecutively recruited from glaucoma clinics. Indentation gonioscopy and dark room SS-OCT were performed. Gonioscopic angle closure was defined as non-visibility of the posterior trabecular meshwork in ≥180° of the angle. For each ...

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    21. Using image data to numerically correct the jitter in polarization depth encoding PS-OCT

      Using image data to numerically correct the jitter in polarization depth encoding PS-OCT

      In swept source polarization depth encoding polarization sensitive optical coherence tomography (PS-OCT), the laser jitter induces additional noise to the polarization sensitive measurement. In this Letter, we developed a numerical algorithm to correct the jitter phases based on the image data using the Mueller matrix calculus. The algorithm was demonstrated on in vivo retina imaging of a guinea pig with a custom-built PS-OCT system. The performance of the proposed algorithm was almost comparable to the conventional method of using a physical calibration signal. By not requiring a hardware generated calibration signal and k -clock, the proposed algorithm is useful to ...

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    22. Role of anterior segment optical coherence tomography angiography in assessing limbal vasculature in acute chemical injury of the eye

      Role of anterior segment optical coherence tomography angiography in assessing limbal vasculature in acute chemical injury of the eye

      Purpose: To study the role of two anterior segment optical coherence tomography angiography (AS-OCTA) systems in eyes with acute chemical injury. Methods: Prospective study in subjects with unilateral chemical injuries. Sequential slit-lamp assessment with spectral domain (SD) (AngioVue, Optovue, USA) and swept source (SS) (Plex Elite, Zeiss, Carl Zeiss Meditec, Dublin, California, USA) AS-OCTA was performed in both eyes within 24-48 hours of injury. Subjects were managed with a standard clinical protocol and followed-up for 3 months. We assessed limbal disruption (loss of normal limbal vessel architecture), limbal vessel density measurements and agreement (kappa coefficient, κ) between masked assessors of limbal ...

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    23. Optical Coherence Tomography Angiography Monitors Cutaneous Wound Healing under Angiogenesis-Promoting Treatment in Diabetic and Non-Diabetic Mice

      Optical Coherence Tomography Angiography Monitors Cutaneous Wound Healing under Angiogenesis-Promoting Treatment in Diabetic and Non-Diabetic Mice

      During wound healing, the rapid re-establishment of a functional microcirculation in the wounded tissue is of utmost importance. We applied optical coherence tomography (OCT) angiography to evaluate vascular remodeling in an excisional wound model in the pinnae of C57BL/6 and db/db mice receiving different proangiogenic topical treatments. Analysis of the high-resolution OCT angiograms, including the four quantitative parameters vessel density, vessel length, number of bifurcations, and vessel tortuosity, revealed changes of the microvasculature and allowed identification of the overlapping wound healing phases hemostasis, inflammation, proliferation, and remodeling. Angiograms acquired in the inflammatory phase in the first days showed ...

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    24. 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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