1. Articles from Michael J. Collins

    1-18 of 18
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. Anterior segment optical coherence tomography scanning protocols and corneal thickness repeatability

      Anterior segment optical coherence tomography scanning protocols and corneal thickness repeatability

      Purpose To examine the influence of anterior segment optical coherence tomography imaging protocols on the intraobserver and intrasession repeatability of epithelial, stromal, and total corneal thickness measurements. Methods Repeated anterior segment optical coherence tomography (AS-OCT) images (Spectralis, Heidelberg) were obtained from 15 adults using single 8.3 mm wide horizontal line scans with an average of 2, 10, 20, 30, 50 and 100 B-scans. Volumetric scans consisting of nine 8.3 mm horizontal line scans encompassing a 1.3 mm vertical region were also captured (with 20 B-scans per line scan). Single point thickness measures (at the normal to the ...

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    8. 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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    9. Repeatability of wide‐field choroidal thickness measurements using enhanced‐depth imaging optical coherence tomography

      Repeatability of wide‐field choroidal thickness measurements using enhanced‐depth imaging optical coherence tomography

      Background To examine the repeatability of choroidal thickness measurements across a 55° field, in a sample of healthy young adults using wide‐field enhanced‐depth imaging optical coherence tomography. Methods High‐resolution wide‐field volumetric enhanced‐depth imaging scans were obtained from the right eye of 27 adults (mean age 27 ± 5 years) during two sessions, separated by 19 ± 15 days, using the follow‐up feature of the Spectralis instrument, while controlling for confounding factors known to influence choroidal thickness. Semi‐automatic segmentation of the choroidal boundaries was corrected by a single masked observer. This process was repeated on images ...

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    10. Choroidal changes in human myopia: insights from optical coherence tomography imaging

      Choroidal changes in human myopia: insights from optical coherence tomography imaging

      The choroid is a vascular tissue which plays a range of critical roles in the normal physiology of the eye, such as supplying the outer retina with oxygen and nutrients and the regulation of intraocular pressure. There is also substantial evidence, particularly from animal studies, that the choroid plays an important role in the regulation of eye growth and the development of common refractive errors like myopia. In recent years, advances in optical coherence tomography technology have improved our ability to image and measure the choroid in the human eye. Research using this technology over the past decade has dramatically ...

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    11. Impact of image averaging on wide‐field choroidal thickness measurements using enhanced‐depth imaging optical coherence tomography

      Impact of image averaging on wide‐field choroidal thickness measurements using enhanced‐depth imaging optical coherence tomography

      Background The aim of this study was to examine the influence of B‐scan averaging on choroidal thickness using wide‐field enhanced‐depth imaging optical coherence tomography. Methods Six high‐resolution trans‐foveal horizontal enhanced‐depth imaging line scans (spanning a 60° field) were acquired consecutively from the right eye of 10 healthy adults (mean age 30 ± 5 years), with each line scan an average of 10, 20, 30, 40, 50 or 100 B‐scans, using the automated real‐time image averaging and follow‐up features of a Spectralis device. The impact of B‐scan averaging on regional measures of ...

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    12. Optical coherence tomography and scleral contact lenses: clinical and research applications

      Optical coherence tomography and scleral contact lenses: clinical and research applications

      Anterior segment optical coherence tomography (OCT) provides a wealth of opportunities for modern contact lens practice. OCT imaging has numerous clinical and research applications related to the tear film, cornea, conjunctiva, sclera and ocular adnexae, in addition to soft, rigid, and hybrid contact lenses. This review summarises the potential use of OCT imaging in modern scleral contact lens practice including initial lens selection, assessing the scleral contact lens fit with respect to the cornea and sclera, and accurately quantifying the ocular response to lens wear. Recent advances in the understanding of anterior segment metrics including scleral thickness, curvature, toricity, and ...

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    13. 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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    14. 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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    15. 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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    16. 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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    17. 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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    18. 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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    1-18 of 18
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    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 Optical coherence tomography and scleral contact lenses: clinical and research applications Choroidal changes in human myopia: insights from optical coherence tomography imaging Automatic choroidal segmentation in OCT images using supervised deep learning methods Retinal Boundary Segmentation in Stargardt Disease Optical Coherence Tomography Images Using Automated PREcise Percutaneous Coronary Intervention for Stent OptimizatION in Treatment of COMPLEX Lesion (PRECISION-COMPLEX) Real-Time Risk Score for Glaucoma Mass Screening by Spectral Domain Optical Coherence Tomography: Development and Validation