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    1. Retinal Neurovascular Impairment in Patients with Essential Hypertension: An Optical Coherence Tomography Angiography Study

      Retinal Neurovascular Impairment in Patients with Essential Hypertension: An Optical Coherence Tomography Angiography Study

      Purpose : To investigate retinal neurovascular structural changes in patients with essential hypertension. Methods : This observational cross-sectional study consisted of 199 right eyes from 169 nondiabetic essential hypertensive patients, divided into groups as follows: group A, 113 patients with hypertensive retinopathy (HTNR); group B, 56 patients without HTNR; and a control group of 30 healthy subjects. Peripapillary retinal nerve fiber layer (RNFL), radial peripapillary segmented (RPC), ganglion cell–inner plexiform layer (GC-IPL), and superficial (SVP) and deep (DVP) vascular plexus density at the macula (6 × 6 mm 2 ) were measured by optical coherence tomography angiography (OCTA). Results : DVP density was significantly ...

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    2. Ultrahigh Resolution Spectral Domain Optical Coherence Tomography for the Assessment of Micro-Structural Changes in Central Serous Chorioretinopathy: A Pilot Study.

      Ultrahigh Resolution Spectral Domain Optical Coherence Tomography for the Assessment of Micro-Structural Changes in Central Serous Chorioretinopathy: A Pilot Study.

      Purpose : In central serous chorioretinopathy (CSCR), choroidal hyperpermeability associated with retinal pigment epithelium (RPE) impairment causes a leakage of fluid from the choroid into the subretinal space, with potential damage to the photoreceptors. We hypothesize that ultrahigh-resolution spectral domain optical coherence tomography (UHR SD-OCT) will enable more detailed assessment of structural changes in this condition. Methods : Patients in all stages of CSCR (acute, chronic and post-resolution) were imaged using an UHR SD-OCT prototype, with an 850 nm center wavelength and an axial resolution of ~2.7 µm in tissue at a 128kHz A-scan rate. Volumetric cube scans and high-density (HD ...

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    3. Evaluating the long-term effects of anti-vascular endothelial growth factor therapy on choroidal neovascularization in age-related macular degeneration using optical coherence tomography angiography

      Evaluating the long-term effects of anti-vascular endothelial growth factor therapy on choroidal neovascularization in age-related macular degeneration using optical coherence tomography angiography

      Purpose : Optical coherence tomography angiography (OCTA) allows for precise, non-invasive monitoring of changes to choroidal neovascularization (CNV) structure over time. The short-term effects of anti-vascular endothelial growth factor (anti-VEGF) treatment on CNV morphology is well described, but long-term studies on morphologic changes and correlation of such to the type of CNV have not been conducted. This study aims to determine if different types of CNVs in neovascular AMD (nAMD) behave differently with anti-VEGF treatment as visualized on OCTA. Methods : AMD Patients with treatment naive type 1, type 2, and type 3 CNVs were retrospectively screened for baseline and follow-up OCTA ...

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    4. Bringing Deep Learning Models to the Data: An Application in Recognizing Intra-Retinal Fluid on Optical Coherence Tomography (OCT) Images

      Bringing Deep Learning Models to the Data: An Application in Recognizing Intra-Retinal Fluid on Optical Coherence Tomography (OCT) Images

      Purpose : Amidst intense interest in deep learning in medicine, concerns regarding data privacy, security, and sharing are of increasing importance. A model-to-data approach, in which the model itself is transferred rather than data, can circumvent many of these challenges, but has not been previously tested in ophthalmology. The objective of our study was to determine whether a model-to-data deep learning approach (i.e. validation of the algorithm without any data transfer) can be successfully applied for the first time to deep learning in ophthalmology. Methods : This is a cross sectional study in which a deep learning algorithm model developed at ...

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    5. A machine learning method for optical coherence tomography scan quality assessment

      A machine learning method for optical coherence tomography scan quality assessment

      Purpose : The reliability of automated analysis of optical coherence tomography (OCT) scans depends on the scan quality. Quality indicators in commercial instruments only provide an overall score and do not provide localized information. Here we demonstrated a quality map using a semi-supervised machine learning technique which can aid with identifying local areas of poor quality. Methods : Our method first computes a set of feature maps using signal strength, signal-to-noise ratio (SNR), and contrast for individual or a group of neighboring A-scans of 580 6x6x2mm OCT volumes with good and poor quality (Fig 1A shows one volume). It then combines the ...

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    6. Clustering Spectral-Domain Optical Coherence Tomography Images using a Deep Variational Auto-encoder

      Clustering Spectral-Domain Optical Coherence Tomography Images using a Deep Variational Auto-encoder

      Purpose : To learn a low-dimensional representation of spectral-domain optical coherence tomography (SD OCT) peripapillary images that can be used to classify images into glaucoma versus healthy eyes. Methods : The study included 23,992 Spectralis SD OCT images from 1,336 eyes, of which 30% were healthy and the remaining were glaucoma or glaucoma suspects. The definition of groups was based on visual fields and inspection of the optic nerve. In order to learn a low-dimensional representation of the high-dimensional SD OCT images a variational auto-encoder (VAE) was used, an unsupervised deep learning technique. The encoder and decoder of the VAE ...

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      Mentions: Duke University
    7. Improved Denoising of Optical Coherence Tomography via Repeated Acquisitions and Unsupervised Deep Learning

      Improved Denoising of Optical Coherence Tomography via Repeated Acquisitions and Unsupervised Deep Learning

      Purpose : Optical Coherence Tomography (OCT) is widely used, yet its interpretation is confounded by strong speckle noise. Previous denoising methods make strong assumptions on noise characteristics and struggle to retain fine structure. We present a data-driven registration and denoising method which vastly improves image fidelity while requiring only repeated noisy acquisitions of individual subjects. Methods : Noise2Noise is an unsupervised denoising approach for repeatedly acquired noisy images (Lehtinen, ICML , 2018). By training a convolutional neural network on noisy image pairs with zero-mean noise, the mean of the clean image distribution is learned. However, repeats are assumed to vary only in noise ...

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    8. Imaging artifacts in widefield optical coherence tomography angiography in patients with retinitis pigmentosa

      Imaging artifacts in widefield optical coherence tomography angiography in patients with retinitis pigmentosa

      Purpose : Optical coherence tomography angiography (OCTA) provides high-resolution images of retinal vasculature whereby vessel density (VD) can be used as an outcome marker. VD is diminished in patients with retinitis pigmentosa (RP) but its quantification can be confounded by imaging artifacts. In this retrospective study, we investigate artifacts that may affect the clinical application of widefield OCTA (WF-OCTA) in patients with RP. Methods : University of Kentucky IRB (#48463) approved retrospective analysis of WF-OCTA images from 33 subjects with a diagnosis of RP and 12x12mm OCTA imaging (Plex Elite 9000, Zeiss, Dublin, CA). Images form the eye with higher signal strength ...

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    9. Functional optical coherence tomography of photoreceptor outer and inner segments in living eye.

      Functional optical coherence tomography of photoreceptor outer and inner segments in living eye.

      Purpose : This study is to investigate stimulus-evoked intrinsic optical signal (IOS) changes in photoreceptor outer segment (OS) and inner segment (IS), and thus to demonstrate the potential of functional IOS imaging of phototransduction and metabolic integrity of retinal photoreceptor. Methods : A custom-designed optical coherence tomography (OCT) was used for in vivo imaging of transient IOS changes in the retina of wild-type mice (C57BL/6J). A near-infrared superluminescent diode (SLD) was used as the light source for OCT imaging, and a visible light-emitting diode (LED) was employed for retinal stimulation. Depth-resolved IOSs were calculated at individual retina layers, based on the ...

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    10. Effects of water drinking test on ocular blood flow using optical coherence tomography angiography

      Effects of water drinking test on ocular blood flow using optical coherence tomography angiography

      Purpose : Increased intraocular pressure (IOP) is a major risk factor for the development of glaucoma and its progression. Literature has proposed the water drinking test (WDT) as a practical method to predict the IOP peak of diurnal tension curve. This preliminary study assesses changes in macular and peripapillary vascular microcirculation using optical coherence tomography angiography (OCTA) metrics after WDT in healthy eyes. Methods : Five healthy subjects (age 37±7.9 years) underwent the WDT, which involved drinking a 1-liter water load in 5 minutes after 4 hours of fasting. IOP using non-contact tonometry and OCTA scans from CIRRUS™ 6000 AngioPlex ...

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    11. Impact of retinal dewarping on thickness measurements in widefield optical coherence tomography volumes

      Impact of retinal dewarping on thickness measurements in widefield optical coherence tomography volumes

      Purpose : Recent developments in optical coherence tomography (OCT) imaging have demonstrated widefield imaging up to 90° field of view (FOV). The purpose of this study is to develop a two-dimensional dewarping method for retinal OCT volumes and to evaluate the impact of retinal dewarping on thickness measurements. Methods : The method developed by Steidle (Biophotonics: Photonic Solutions for Better Health Care VI, 2018) was expanded to dewarp widefield OCT volumes. A digital model dataset of two retinal layers with a thickness of 200 µm was created. We compared the traditional thickness measurement along the OCT A-scan with a thickness measurement that ...

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    12. 3D Image Registration Based Atlas for Large Field of View Human Eye Optical Coherence Tomography

      3D Image Registration Based Atlas for Large Field of View Human Eye Optical Coherence Tomography

      Purpose : Optical coherence tomography (OCT) is a non-invasive imaging modality used for high resolution (10 μ) imaging of ocular tissue. Retinal cell layers are clearly visible on OCT providing a means for quantitative and topographical analysis. Medical atlases are important tools for detecting abnormal structural and anatomical tissue alterations, relative to a standardized normal. They can also serve as a reference for registration of individual images for deformation-based analysis. The purpose of the current study is to present a method for generating an atlas of the human eye using large field of view 3D OCT image volumes. Methods : Imaging was performed ...

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    13. Multi-label multi-task macular Optical Coherence Tomography (OCT) scans classification system

      Multi-label multi-task macular Optical Coherence Tomography (OCT) scans classification system

      Purpose : Macular OCT cubes generally contain multiple B-scans, making the clinical decision time-consuming and tedious. For an effective and fast clinical decision, it is essential to develop an automatic algorithm that identifies the anomalous cube and B-scans, the pathologies present within the B-scans, and overall disease. We present an algorithm that predicts whether the B-scan contains abnormality or not along with the presence of multiple pathologies and also the cube level abnormalities. Methods : The multi-label multi-task algorithm is developed in two phases using 1485 OCT macular cubes (75,264 B-scans) of 328 subjects (132 normal, 196 with macular pathologies) acquired ...

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    14. Ultrahigh-Resolution Optical Coherence Tomography Investigation of Age-Related Changes in the Photoreceptors, Retinal Pigment Epithelium and Bruch’s Membrane

      Ultrahigh-Resolution Optical Coherence Tomography Investigation of Age-Related Changes in the Photoreceptors, Retinal Pigment Epithelium and Bruch’s Membrane

      Purpose : Aging is the biggest risk factor for age-related macular degeneration (AMD). Previous histological and ultrastructural studies have suggested that photoreceptors (PR), retinal pigment epithelium (RPE), and Bruch’s membrane (BM) undergo changes with aging and in AMD. A new high-speed, ultrahigh-resolution optical coherence tomography (UHR OCT) prototype instrument with depth tracking and software motion correction was used to investigate PR/RPE/BM alterations in normal aging and early AMD. Methods : We developed a high-speed UHR OCT instrument with 2.7 µm axial resolution and 128 kHz A-scan rate. A galvanometer scanner actuates the OCT reference arm to match the ...

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    15. Detection of Venous Loops in Diabetic Retinopathy using Widefield Swept-Source Optical Coherence Tomography Angiography

      Detection of Venous Loops in Diabetic Retinopathy using Widefield Swept-Source Optical Coherence Tomography Angiography

      Purpose : Retinal venous loops (RVL) are rare manifestations of diabetic retinopathy (DR) usually identified by color fundus photography. The prevalence and its predictive value reported in the literature may be underestimated due to the limitations of detection techniques. This study investigated the prevalence of RVL and their associated microvascular changes using widefield swept-source optical coherence tomography angiography (WF SS-OCTA). Methods : In this retrospective, observational study at Mass Eye and Ear from December 2018 to December 2019, diabetic patients with proliferative diabetic retinopathy (PDR), non-proliferative diabetic retinopathy (NPDR) and without DR were included. All patients were imaged with a WF SS-OCTA ...

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    16. Impacts of Axial Length on Retinal and Choriocapillaris Blood Flow Quantification in Myopia with Swept-Source Optical Coherence Tomography Angiography

      Impacts of Axial Length on Retinal and Choriocapillaris Blood Flow Quantification in Myopia with Swept-Source Optical Coherence Tomography Angiography

      Purpose : To evaluate the impact of image magnification correction on retinal and choriocapillaris (CC) blood flow quantification using swept-source optical coherence tomography angiography (OCTA) in myopic eyes. Methods : Subjects with myopia were recruited for ocular biometry, refraction, and OCTA imaging with a 6 × 6-mm protocol. The retinal vascular area density (RVAD), retinal vascular skeleton density (RVSD), retinal flow impairment area (RFIA), percentage of CC flow deficits (FD%), and the mean size of CC flow deficits (FDs) were quantified within a 5-mm-diameter circle centered on the fovea before and after magnification correction using the Littman and the modified Bennett formulae. Results ...

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    17. Retinal capillary perfusion heterogeneity in diabetic retinopathy detected by optical coherence tomography angiography

      Retinal capillary perfusion heterogeneity in diabetic retinopathy detected by optical coherence tomography angiography

      Purpose : To investigate the ability of a commercially available optical coherence tomography angiography (OCTA) machine to describe retinal capillary perfusion heterogeneity in diabetic retinopathy (DR) patients. Methods : Ten consecutive en face 6x6mm foveal OCTA images were obtained from both eyes of 13 DR patients and 5 healthy controls using a Zeiss PLEX Elite 9000. Fifteen DR and eight healthy eyes met the inclusion criteria: a centered fovea, little motion artifacts, and a signal of at least 8/10 in all frames. Each eye was analysed for capillary perfusion changes between frames in the superficial and deep capillary plexuses (SCP and ...

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    18. Atlas of Human Retinal Pigment Epithelium Organelles Significant for Clinical Imaging

      Atlas of Human Retinal Pigment Epithelium Organelles Significant for Clinical Imaging

      Purpose : To quantify organelles impacting imaging in the cell body and intact apical processes of human retinal pigment epithelium (RPE), including melanosomes, lipofuscin–melanolipofuscin (LM), mitochondria, and nuclei. Methods : A normal perifovea of a 21-year-old white male was preserved after rapid organ recovery. An aligned image stack was generated using serial block-face scanning electron microscopy and was annotated by expert readers (TrakEM, ImageJ). Acquired measures included cell body and nuclear volume ( n = 17); organelle count in apical processes ( n = 17) and cell bodies ( n = 8); distance of cell body organelles along a normalized apical–basal axis ( n = 8); and dimensions ...

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    19. Optical Coherence Tomography Angiography Quantitative Assessment of Macular Neovascularization in Best Vitelliform Macular Dystrophy

      Optical Coherence Tomography Angiography Quantitative Assessment of Macular Neovascularization in Best Vitelliform Macular Dystrophy

      Purpose : To describe quantitative characteristics of macular neovascularization (MNV) in vitelliform macular dystrophy (VMD) patients by means of optical coherence tomography angiography (OCTA). Methods : The study design was a prospective case series. All patients underwent complete ophthalmologic assessment, optical coherence tomography, and OCTA. The quantitative OCTA parameters examined included vessel tortuosity and vessel dispersion of the MNV. The primary outcome was OCTA characterization of MNV in VMD. Secondary outcomes included the evolution of MNV over the follow-up. Results : A total of 78 eyes were recruited for the study. MNV was identified in 50 eyes (64%) at baseline and in 51 ...

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    20. Longitudinal Structural and Microvascular Observation in RCS Rat Eyes Using Optical Coherence Tomography Angiography

      Longitudinal Structural and Microvascular Observation in RCS Rat Eyes Using Optical Coherence Tomography Angiography

      Purpose : To evaluate the change of retinal thickness and ocular microvasculature in a rat model of retinitis pigmentosa using swept source optical coherence tomography angiography (SS-OCTA) Methods : Three-weeks-old Royal College of Surgeons (RCS) rats ( n = 8) and age-matched control rats ( n = 14) were imaged by a prototype SS-OCTA system. Follow-up measurements occurred every three weeks on six RCS rats until week 18, and cross-sectional measurements were conducted on control rats. Thicknesses of different retinal layers and the total retina were measured. The enface angiograms from superficial vascular plexiform (SVP) and deep capillary plexiform (DCP) were analyzed, and the image sharpness ...

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    21. Imaging of Macrophage-Like Cells in Living Human Retina Using Clinical OCT

      Imaging of Macrophage-Like Cells in Living Human Retina Using Clinical OCT

      Purpose : To image retinal macrophages at the vitreoretinal interface in the living human retina using a clinical optical coherence tomography (OCT) device. Methods : Eighteen healthy controls and three patients with retinopathies were imaged using a clinical spectral-domain OCT. In controls, 10 sequential scans were collected at three different locations: (1) ∼9 degrees temporal to the fovea, (2) the macula, and (3) the optic nerve head (ONH). Intervisit repeatability was evaluated by imaging the temporal retina twice on the same day and 3 days later. Only 10 scans at the temporal retina were obtained from each patient. A 3-µm OCT ...

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    22. Retinal Vascular Reactivity in Type 1 Diabetes Patients Without Retinopathy Using Optical Coherence Tomography Angiography

      Retinal Vascular Reactivity in Type 1 Diabetes Patients Without Retinopathy Using Optical Coherence Tomography Angiography

      Purpose : We hypothesize that patients with type 1 diabetes (T1D) may have abnormal retinal vascular responses before diabetic retinopathy (DR) is clinically evident. Optical coherence tomography angiography (OCTA) was used to dynamically assess the retinal microvasculature of diabetic patients with no clinically visible retinopathy. Methods : Controlled nonrandomized interventional study. The studied population included 48 eyes of 24 T1D patients and 24 demographically similar healthy volunteers. A commercial OCTA device (AngioVue) was used, and two tests were applied: (1) the hypoxia challenge test (HCT) and (2) the handgrip test to induce a vasodilatory or vasoconstrictive response, respectively. The HCT is a ...

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    23. Volume Rendering of Dense B-Scan Optical Coherence Tomography Angiography to Evaluate the Connectivity of Macular Blood Flow

      Volume Rendering of Dense B-Scan Optical Coherence Tomography Angiography to Evaluate the Connectivity of Macular Blood Flow

      Purpose : To characterize macular blood flow connectivity using volume rendering of dense B-scan (DB) optical coherence tomography angiography (OCTA) data. Methods : This was a prospective, cross-sectional, observational study. DB OCTA perifoveal scans were performed on healthy subjects using the Spectralis HRA+OCT2. A volumetric projection artifact removal algorithm and customized filters were applied to raw OCTA voxel data. Volume rendering was performed using a workflow on Imaris 9.5 software. Vascular graphs were obtained from angiographic data using the algorithm threshold-loops. Superficial arteries and veins were identified from color fundus photographs and connections between adjacent arteries and veins displayed using ...

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    24. Quasi-Static Optical Coherence Elastography to Characterize Human Corneal Biomechanical Properties

      Quasi-Static Optical Coherence Elastography to Characterize Human Corneal Biomechanical Properties

      Purpose : Quasi-static optical coherence elastography (OCE) is an emerging technology to investigate corneal biomechanical behavior in situations similar to physiological stress conditions. Herein OCE was applied to evaluate previously inaccessible biomechanical characteristics of human corneal tissue and to study the role of Bowman's layer in corneal biomechanics. Methods : Human corneal donor buttons ( n = 23) were obtained and Descemet's membrane and endothelium were removed. In 11 corneas, Bowman's layer was ablated by a 20 µm stromal excimer laser ablation. Buttons were mounted on an artificial anterior chamber and subjected to a pressure modulation from 10 to 30 mm ...

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