1. Articles from David Alonso-Caneiro

    1-24 of 24
    1. High-Density Optical Coherence Tomography Analysis Provides Insights Into Early/Intermediate Age-Related Macular Degeneration Retinal Layer Changes

      High-Density Optical Coherence Tomography Analysis Provides Insights Into Early/Intermediate Age-Related Macular Degeneration Retinal Layer Changes

      Purpose: To topographically map all of the thickness differences in individual retinal layers between early/intermediate age-related macular degeneration (AMDearly/AMDint) and normal eyes and to determine interlayer relationships. Methods: Ninety-six AMDtotal (48 AMDearly and 48 AMDint) and 96 normal eyes from 192 participants were propensity-score matched by age, sex, and refraction. Retrospective optical coherence tomography (OCT) macular cube scans were acquired, and high-density (60 × 60 0.01-mm2) grid thicknesses were custom extracted for comparison between AMDtotal and normal eyes corrected for confounding. Resultant "normal differences" underwent cluster, interlayer correlation, and dose-response analyses for the retinal nerve fiber layer (RNFL ...

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    2. Prediction of visual field defects from macular optical coherence tomography in glaucoma using cluster analysis

      Prediction of visual field defects from macular optical coherence tomography in glaucoma using cluster analysis

      Purpose To assess the accuracy of cluster analysis-based models in predicting visual field (VF) defects from macular ganglion cell-inner plexiform layer (GCIPL) measurements in glaucomatous and healthy cohorts. Methods GCIPL measurements were extracted from posterior pole optical coherence tomography (OCT), from locations corresponding to central VF test grids. Models incorporating cluster analysis methods and corrections for age and fovea to optic disc tilt were developed from 493 healthy participants, and 5th and 1st percentile limits of GCIPL thickness were derived. These limits were compared with pointwise 5th and 1st percentile limits by calculating sensitivities and specificities in an additional 40 ...

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    3. Anterior segment optical coherence tomography (AS-OCT) image analysis methods and applications: A systematic review

      Anterior segment optical coherence tomography (AS-OCT) image analysis methods and applications: A systematic review

      Background: Anterior segment optical coherence tomography (AS-OCT) constitutes an important imaging modality to examine the anterior eye, which is commonly used in research and clinical practice. Since its introduction, a range of image analysis methods have been developed to quantify these images using different analysis techniques for various applications. This systematic review aims to provide an in-depth summary and to classify image analysis techniques found in the literature applied to AS-OCT images. Methods: Scopus and Engineering Village databases were searched to retrieve relevant studies up to and including January 2022. Customized search statements were used along with cross reference and ...

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    4. Changes in Retinal Optical Coherence Tomography Angiography Indexes Over 24 Hours

      Changes in Retinal Optical Coherence Tomography Angiography Indexes Over 24 Hours

      Purpose: To evaluate changes in the retinal microvasculature of young adults over 24 hours using optical coherence tomography angiography (OCT-A). Methods: Participants (n = 44, mean age 23.2 ± 4.1 years, 24 myopes and 20 nonmyopes) with normal ophthalmological findings were recruited. Two macular OCT-A and OCT scans, systemic blood pressure, intraocular pressure (IOP), and biometry measurements were taken every four hours over 24 hours. Superficial and deep retinal layer en face images were analyzed to extract magnification-corrected vascular indexes using image analysis including foveal avascular zone metrics, vessel density, and perfusion density for the foveal, parafoveal, and perifoveal zones ...

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    5. OCT Retinal and Choroidal Layer Instance Segmentation Using Mask R-CNN

      OCT Retinal and Choroidal Layer Instance Segmentation Using Mask R-CNN

      Optical coherence tomography (OCT) of the posterior segment of the eye provides high-resolution cross-sectional images that allow visualization of individual layers of the posterior eye tissue (the retina and choroid), facilitating the diagnosis and monitoring of ocular diseases and abnormalities. The manual analysis of retinal OCT images is a time-consuming task; therefore, the development of automatic image analysis methods is important for both research and clinical applications. In recent years, deep learning methods have emerged as an alternative method to perform this segmentation task. A large number of the proposed segmentation methods in the literature focus on the use of ...

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    6. Application of Deep Learning Methods for Binarization of the Choroid in Optical Coherence Tomography Images

      Application of Deep Learning Methods for Binarization of the Choroid in Optical Coherence Tomography Images

      Purpose: The purpose of this study was to develop a deep learning model for automatic binarization of the choroidal tissue, separating choroidal blood vessels from nonvascular stromal tissue, in optical coherence tomography (OCT) images from healthy young subjects. Methods: OCT images from an observational longitudinal study of 100 children were used for training, validation, and testing of 5 fully semantic networks, which provided a binarized output of the choroid. These outputs were compared with ground truth images, generated from a local binarization technique after manually optimizing the analysis window size for each individual image. The performance was evaluated using accuracy ...

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    7. Ganglion cell-inner plexiform layer measurements derived from widefield compared to montaged 9-field optical coherence tomography

      Ganglion cell-inner plexiform layer measurements derived from widefield compared to montaged 9-field optical coherence tomography

      Purpose: To compare ganglion cell-inner plexiform layer (GCIPL) thicknesses obtained using a single WF-OCT scan and standard composite OCT scans acquired in 9 fields of gaze (9F-OCT). Methods: Thirteen healthy participants underwent WF-OCT and 9F-OCT using the Spectralis OCT. The GCIPL was automatically segmented with a manual review for 9F-OCT and was manually segmented for WF-OCT. After registration, differences in GCIPL thicknesses were compared using 95% confidence intervals computed from one-sample t-tests and Bland-Altman analyses. Location-specific differences in B-scan tilt were analysed using Spearman correlations and linear regression models. To determine whether B-scan tilt influences GCIPL measurements, regression models of ...

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    8. Quantitative compressive optical coherence elastography using structural OCT imaging and optical palpation to measure soft contact lens mechanical properties

      Quantitative compressive optical coherence elastography using structural OCT imaging and optical palpation to measure soft contact lens mechanical properties

      In this study, the principle of ‘optical palpation’ was applied to a compression optical coherence elastography (OCE) method using spectral domain optical coherence tomography (OCT). Optical palpation utilizes a compliant transparent material of known mechanical properties, which acts as a stress sensor, in order to derive the mechanical properties of a sample material under examination. This technique was applied to determine the mechanical properties of soft contact lenses, with one lens being used as the compliant stress sensor and the other as the sample under investigation to extract the mechanical properties. This compliant stress sensor allowed for the stress of ...

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    9. Static compression optical coherence elastography to measure the mechanical properties of soft contact lenses

      Static compression optical coherence elastography to measure the mechanical properties of soft contact lenses

      In this study, a novel method was developed for estimating the elastic modulus (Young's modulus) of soft contact lens materials using static compression optical coherence elastography. Using a commercially available spectral domain optical coherence tomography instrument, an experimental setup was developed to image a soft contact lens sample before and during compression with a known applied force, from which the lens material's mechanical properties can be derived. A semi-automatic segmentation method using graph-search theory and dynamic processing was used to trace the lens boundaries and to determine key structural changes within the images. To validate the method, five ...

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    10. Deep feature loss to denoise OCT images using deep neural networks

      Deep feature loss to denoise OCT images using deep neural networks

      Significance: Speckle noise is an inherent limitation of optical coherence tomography (OCT) images that makes clinical interpretation challenging. The recent emergence of deep learning could offer a reliable method to reduce noise in OCT images. Aim: We sought to investigate the use of deep features (VGG) to limit the effect of blurriness and increase perceptual sharpness and to evaluate its impact on the performance of OCT image denoising (DnCNN). Approach: Fifty-one macula-centered OCT pairs were used in training of the network. Another set of 20 OCT pair was used for testing. The DnCNN model was cascaded with a VGG network ...

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    11. Comparison of Subjective and Objective Methods of Corneoscleral Limbus Identification from Anterior Segment Optical Coherence Tomography Images

      Comparison of Subjective and Objective Methods of Corneoscleral Limbus Identification from Anterior Segment Optical Coherence Tomography Images

      Significance: This study evaluates the reliability and validity of an automatic method of the external and internal limbal points identification from anterior segment optical coherence tomography (OCT) images in comparison with manual delineation. Purpose: The purpose of this work was to evaluate the repeatability and precision of a previously proposed automatic method of external and internal limbal points identification and to compare them with the manual delineation by experienced clinicians in terms of limbus diameter. Methods: Optical coherence tomography tomograms obtained for 12 healthy volunteers without a history of eye diseases were analyzed. Fifteen OCT tomograms were captured for each ...

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    12. Retinal Boundary Segmentation in Stargardt Disease Optical Coherence Tomography Images Using Automated

      Retinal Boundary Segmentation in Stargardt Disease Optical Coherence Tomography Images Using Automated

      Purpose : To use a deep learning model to develop a fully automated method (fully semantic network and graph search [FS-GS]) of retinal segmentation for optical coherence tomography (OCT) images from patients with Stargardt disease. Methods : Eighty-seven manually segmented (ground truth) OCT volume scan sets (5171 B-scans) from 22 patients with Stargardt disease were used for training, validation and testing of a novel retinal boundary detection approach (FS-GS) that combines a fully semantic deep learning segmentation method, which generates a per-pixel class prediction map with a graph-search method to extract retinal boundary positions. The performance was evaluated using the mean absolute ...

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    13. Comparison of Choroidal Thickness Measurements Using Semiautomated and Manual Segmentation Methods

      Comparison of Choroidal Thickness Measurements Using Semiautomated and Manual Segmentation Methods

      SIGNIFICANCE This study demonstrated that a semiautomated segmentation method could help inexperienced practitioners to obtain choroidal thickness as good as experienced practitioners. PURPOSE The purpose of this study was to compare choroidal thickness measurements obtained by semiautomated and manual segmentation methods. METHODS Optical coherence tomography images of 37 eyes from 37 healthy young subjects acquired by a spectral-domain optical coherence tomography device were reviewed retrospectively. Two naive examiners measured choroidal thickness using manual and semiautomated methods, whereas two experienced examiners used only the semiautomated method. The semiautomated method referred to a fully automated segmentation program customized based on MATLAB and ...

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    14. Automatic choroidal segmentation in OCT images using supervised deep learning methods

      Automatic choroidal segmentation in OCT images using supervised deep learning methods

      The analysis of the choroid in the eye is crucial for our understanding of a range of ocular diseases and physiological processes. Optical coherence tomography (OCT) imaging provides the ability to capture highly detailed cross-sectional images of the choroid yet only a very limited number of commercial OCT instruments provide methods for automatic segmentation of choroidal tissue. Manual annotation of the choroidal boundaries is often performed but this is impractical due to the lengthy time taken to analyse large volumes of images. Therefore, there is a pressing need for reliable and accurate methods to automatically segment choroidal tissue boundaries in ...

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    15. Posterior Choroidal Stroma Reduces Accuracy of Automated Segmentation of Outer Choroidal Boundary in Swept Source Optical Coherence Tomography

      Posterior Choroidal Stroma Reduces Accuracy of Automated Segmentation of Outer Choroidal Boundary in Swept Source Optical Coherence Tomography

      Purpose : To determine the influence of choroidal boundary morphology on the accuracy of automated measurements of subfoveal choroidal thickness (SFCT) in swept source optical coherence tomography (SSOCT). Methods : A retrospective image analysis of foveal-centered horizontal line scans from normal and diseased eyes using the Topcon DRI OCT-1 Atlantis SSOCT was conducted. Subfoveal choroid-scleral junction (CSJ) and retina-choroidal junction (RCJ) morphologies were graded by two observers. Automated SFCT (A-SFCT) was compared with manual SFCT (M-SFCT) measurements from Bruch's membrane to the posterior limits of choroidal vessel, hyperreflective stroma, and hyporeflective lamina fusca. Agreement in boundary grading was assessed by Cohen ...

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    16. Enhanced Visualization of Subtle Outer Retinal Pathology by En Face Optical Coherence Tomography and Correlation with Multi-Modal Imaging

      Enhanced Visualization of Subtle Outer Retinal Pathology by En Face Optical Coherence Tomography and Correlation with Multi-Modal Imaging

      Purpose To present en face optical coherence tomography (OCT) images generated by graph-search theory algorithm-based custom software and examine correlation with other imaging modalities. Methods En face OCT images derived from high density OCT volumetric scans of 3 healthy subjects and 4 patients using a custom algorithm (graph-search theory) and commercial software (Heidelberg Eye Explorer software (Heidelberg Engineering)) were compared and correlated with near infrared reflectance, fundus autofluorescence, adaptive optics flood-illumination ophthalmoscopy (AO-FIO) and microperimetry. Results Commercial software was unable to generate accurate en face OCT images in eyes with retinal pigment epithelium (RPE) pathology due to segmentation error at ...

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    17. Tissue thickness calculation in ocular optical coherence tomography

      Tissue thickness calculation in ocular optical coherence tomography

      Thickness measurements derived from optical coherence tomography (OCT) images of the eye are a fundamental clinical and research metric, since they provide valuable information regarding the eye’s anatomical and physiological characteristics, and can assist in the diagnosis and monitoring of numerous ocular conditions. Despite the importance of these measurements, limited attention has been given to the methods used to estimate thickness in OCT images of the eye. Most current studies employing OCT use an axial thickness metric, but there is evidence that axial thickness measures may be biased by tilt and curvature of the image. In this paper, standard ...

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    18. Automatic segmentation of choroidal thickness in optical coherence tomography

      Automatic segmentation of choroidal thickness in optical coherence tomography

      The assessment of choroidal thickness from optical coherence tomography (OCT) images of the human choroid is an important clinical and research task, since it provides valuable information regarding the eye’s normal anatomy and physiology, and changes associated with various eye diseases and the development of refractive error. Due to the time consuming and subjective nature of manual image analysis, there is a need for the development of reliable objective automated methods of image segmentation to derive choroidal thickness measures. However, the detection of the two boundaries which delineate the choroid is a complicated and challenging task, in particular the ...

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    19. Choroidal thickness in myopic and non-myopic children assessed with enhanced depth imaging optical coherence tomography

      Choroidal thickness in myopic and non-myopic children assessed with enhanced depth imaging optical coherence tomography

      Purpose: To examine choroidal thickness (ChT) and its topographical variation across the posterior pole in myopic and non-myopic children. Methods: One hundred and four children aged 10-15 years of age (mean age 13.1±1.4 years) had ChT measured using enhanced depth imaging optical coherence tomography (OCT). Forty one children were myopic (mean spherical equivalent -2.4±1.5D) and 63 were non-myopic (mean +0.3±0.3D). ChT was assessed in a series of 6 radial OCT line scans centred on the fovea for each child. Subfoveal ChT and ChT across a series of parafoveal zones over the ...

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    20. Using Optical Coherence Tomography to Assess Corneoscleral Morphology After Soft Contact Lens Wear

      Using Optical Coherence Tomography to Assess Corneoscleral Morphology After Soft Contact Lens Wear
      Purpose. To evaluate the use of optical coherence tomography (OCT) for assessing the effect of different soft contact lenses on corneoscleral morphology. Methods. Ten subjects had anterior segment OCT B-scans taken in the morning and again after 6 h of soft contact lens wear. For each subject, three different contact lenses were used in the right eye on non-consecutive days, including a hydrogel sphere, a silicone hydrogel sphere, and a silicone hydrogel toric. After image registration and layer segmentation, analyses were performed of the first hyper-reflective layer (HRL), the epithelial basement membrane (EBL), and the epithelial thickness (HRL to EBL ...
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    21. Diurnal Variation of Retinal Thickness with Spectral Domain OCT

      Diurnal Variation of Retinal Thickness with Spectral Domain OCT

      Purpose. To investigate whether diurnal variation occurs in retinal thickness measures derived from spectral domain optical coherence tomography (SD-OCT). Methods. Twelve healthy adult subjects had retinal thickness measured with SD-OCT every 2 h over a 10 h period. At each measurement session, three average B-scan images were derived from a series of multiple B-scans (each from a 5 mm horizontal raster scan along the fovea, containing 1500 A-scans/B-scan) and analyzed to determine the thickness of the total retina, as well as the thickness of the outer retinal layers. Average thickness values were calculated at the foveal center, at the ...

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    22. Speckle reduction in optical coherence tomography imaging by affine-motion image registration

      Speckle reduction in optical coherence tomography imaging by affine-motion image registration
      Signal-degrading speckle is one factor that can reduce the quality of optical coherence tomography images. We demonstrate the use of a hierarchical model-based motion estimation processing scheme based on an affine-motion model to reduce speckle in optical coherence tomography imaging, by image registration and the averaging of multiple B-scans. The proposed technique is evaluated against other methods available in the literature. The results from a set of retinal images show the benefit of the proposed technique, which provides an improvement in signal-to-noise ratio of the square root of the number of averaged images, leading to clearer visual information in the ...
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    23. Feature Of The Week 11/6/11: Nicolaus Copernicus University Researchers Develop Technique to Study Biomechanical Properties of The Cornea Using OCT

      Feature Of The Week 11/6/11: Nicolaus Copernicus University Researchers Develop Technique to Study Biomechanical Properties of The Cornea Using OCT
      Researchers from Nicolaus Copernicus University have a long history of development of OCT in general and ophthalmology in particular. Recently NCU developed a technique to study the mechanical dynamics of the cornea using high speed OCT combined with an air puff system. Below is a summary of their work.We present a novel method and instrument for in vivo imaging and measurement of the human corneal dynamics during an air puff. The instrument is based on high-speed swept source optical coherence tomography (ssOCT) combined with a custom adapted air puff chamber from a non-contact tonometer, which uses an air stream ...
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    24. Assessment of corneal dynamics with high-speed swept source Optical Coherence Tomography combined with an air puff system

      Assessment of corneal dynamics with high-speed swept source Optical Coherence Tomography combined with an air puff system
      We present a novel method and instrument for in vivo imaging and measurement of the human corneal dynamics during an air puff. The instrument is based on high-speed swept source optical coherence tomography (ssOCT) combined with a custom adapted air puff chamber from a non-contact tonometer, which uses an air stream to deform the cornea in a non-invasive manner. During the short period of time that the deformation takes place, the ssOCT acquires multiple A-scans in time (M-scan) at the center of the air puff, allowing observation of the dynamics of the anterior and posterior corneal surfaces as well as ...
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    1-24 of 24
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    Assessment of corneal dynamics with high-speed swept source Optical Coherence Tomography combined with an air puff system Feature Of The Week 11/6/11: Nicolaus Copernicus University Researchers Develop Technique to Study Biomechanical Properties of The Cornea Using OCT Speckle reduction in optical coherence tomography imaging by affine-motion image registration Diurnal Variation of Retinal Thickness with Spectral Domain OCT Using Optical Coherence Tomography to Assess Corneoscleral Morphology After Soft Contact Lens Wear Choroidal thickness in myopic and non-myopic children assessed with enhanced depth imaging optical coherence tomography Automatic segmentation of choroidal thickness in optical coherence tomography Tissue thickness calculation in ocular optical coherence tomography Enhanced Visualization of Subtle Outer Retinal Pathology by En Face Optical Coherence Tomography and Correlation with Multi-Modal Imaging Posterior Choroidal Stroma Reduces Accuracy of Automated Segmentation of Outer Choroidal Boundary in Swept Source Optical Coherence Tomography OCT Macular Volume as a Predictor of Vascular Leakage in Uveitis Vanderbilt University Receives NIH Grant for Smart-phone-integrated, non-invasive, depth-resolved optical spectroscopy for the detection of neonatal jaundice