1. Articles from Peter M. Maloca

    1-14 of 14
    1. Imaging the Vitreous with a Novel Boosted Optical Coherence Tomography Technique: Posterior Vitreous Detachment

      Imaging the Vitreous with a Novel Boosted Optical Coherence Tomography Technique: Posterior Vitreous Detachment

      Purpose: To evaluate the anatomic changes in the vitreous associated with evolving posterior vitreous detachment (PVD) over the macula. Methods: A novel scanning method by which 4 A-scans at each position were averaged prior to the Fourier transform that boosted the image quality sufficiently such that frame averaging could occur. B-scans and volume rendered images of eyes with evidence of any partial separation of the vitreous in the macular regions were evaluated. Results: There were 43 eyes of 23 subjects with particular attention paid to the findings of 7 eyes with various stages of PVD occurring over the macula. In ...

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    2. Imaging the Vitreous with a Novel Boosted Optical Coherence Tomography Technique: Vitreous Degeneration and Cisterns

      Imaging the Vitreous with a Novel Boosted Optical Coherence Tomography Technique: Vitreous Degeneration and Cisterns

      Purpose: To evaluate the degenerative findings including cistern formation in the premacular vitreous using optical coherence tomography (OCT). Methods: A novel enhanced vitreous imaging method by which 4 A-scans at each position were averaged prior to the Fourier transform increased the image quality per frame so that subsequent image registration for averaging could occur. Analysis of B-scans and volume rendered images of eyes in subjects of various ages was performed. Results: There were 43 eyes of 23 subjects ranging in age from 23 - 68 years. The texture in the vitreous images suggests specific orientations of the vitreous fibers in the ...

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    3. Dynamic volume-rendered optical coherence tomography pupillometry

      Dynamic volume-rendered optical coherence tomography pupillometry

      Purpose: To assess intrapupillary space (IPS) changes in healthy subjects with regard to decreased iris motility in patients with pseudoexfoliation glaucoma (PEXG) or non-arteritic anterior ischaemic optic neuropathy (NAION) in a feasibility study in a clinical environment. Methods: Scotopic and photopic IPS measurements using three-dimensionally rendered swept-source optical coherence tomography (SS-OCT) data were obtained and compared for all subjects. Intrapupillary space (IPS) parameters were evaluated such as absolute volumetric differences, relative light response for volumetric ratios and pupillary ejection fraction (PEF) for functional contraction measurements. Results: From a total of 122 IPS from 66 subjects, 106 IPS were eligible for ...

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    4. Uncovering of intraspecies macular heterogeneity in cynomolgus monkeys using hybrid machine learning optical coherence tomography image segmentation

      Uncovering of intraspecies macular heterogeneity in cynomolgus monkeys using hybrid machine learning optical coherence tomography image segmentation

      The fovea is a depression in the center of the macula and is the site of the highest visual acuity. Optical coherence tomography (OCT) has contributed considerably in elucidating the pathologic changes in the fovea and is now being considered as an accompanying imaging method in drug development, such as antivascular endothelial growth factor and its safety profiling. Because animal numbers are limited in preclinical studies and automatized image evaluation tools have not yet been routinely employed, essential reference data describing the morphologic variations in macular thickness in laboratory cynomolgus monkeys are sparse to nonexistent. A hybrid machine learning algorithm ...

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    5. Unraveling the deep learning gearbox in optical coherence tomography image segmentation towards explainable artificial intelligence

      Unraveling the deep learning gearbox in optical coherence tomography image segmentation towards explainable artificial intelligence

      Machine learning has greatly facilitated the analysis of medical data, while the internal operations usually remain intransparent. To better comprehend these opaque procedures, a convolutional neural network for optical coherence tomography image segmentation was enhanced with a Traceable Relevance Explainability (T-REX) technique. The proposed application was based on three components: ground truth generation by multiple graders, calculation of Hamming distances among graders and the machine learning algorithm, as well as a smart data visualization (‘neural recording’). An overall average variability of 1.75% between the human graders and the algorithm was found, slightly minor to 2.02% among human graders ...

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    6. Negative Vessel Remodeling in Stargardt Disease Quantified with Volume-Rendered Optical Coherence Tomography Angiography

      Negative Vessel Remodeling in Stargardt Disease Quantified with Volume-Rendered Optical Coherence Tomography Angiography

      Purpose: To quantify retinal vasculature changes in Stargardt disease1 with volume-rendered optical coherence tomography angiography (OCTA). Methods: OCTA volumes from heathy subjects and two subgroups of STGD1 patients with the presence/absence of definitely decreased autofluorescence (DDAF) areas were compared. OCTA vessel surface area (VSA) and vessel volume (VV) were measured in central zones (Z) of 1, 2 and 3mm diameter. Results: 29 eyes of 15 STGD1 patients (20/9 eyes with/without DDAF) and 30 eyes of 15 controls contributed data. An enlarged foveal avascular zone was found in STGD1 patients without and even more with DDAF associated with ...

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    7. A 3D model to evaluate retinal nerve fiber layer thickness deviations caused by the displacement of optical coherence tomography circular scans in cynomolgus monkeys (Macaca fascicularis)

      A 3D model to evaluate retinal nerve fiber layer thickness deviations caused by the displacement of optical coherence tomography circular scans in cynomolgus monkeys (Macaca fascicularis)

      The main objective of the study was to analyze deviations in retinal nerve fiber layer (RNFL) thickness measurements caused by the displacement of circular optic disc optical coherence tomography scans. High-density radial scans of the optic nerve heads of cynomolgus monkeys were acquired. The retinal nerve fiber layer was manually segmented, and a surface plot of the discrete coordinates was generated. From this plot, the RNFL thicknesses were calculated and compared between accurately centered and intentionally displaced circle scans. Circle scan displacement caused circumpapillary retinal nerve fiber layer thickness deviations of increasing magnitude with increasing center offset. As opposed to ...

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    8. Comparison of Current Optical Coherence Tomography Angiography Methods in Imaging Retinal Hemangioblastomas

      Comparison of Current Optical Coherence Tomography Angiography Methods in Imaging Retinal Hemangioblastomas

      Purpose : To compare spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) for imaging retinal capillary hemangioblastomas (RCHs) in von Hippel-Lindau disease (VHLD). Methods : Prospective single-center cross-sectional study. Tumor size (TS) of perfused RCHs was assessed clinically in relation to the optic disc size. For both technologies, SD-OCTA and SS-OCTA, corresponding images with a scan size of 3 × 3 mm 2 and 6 × 6 mm 2 , respectively, were overlaid according to the set of marker positions to determine the TS. Results : From 200 patients with VHLD, 48 patients showed 84 RCHs. SD-OCTA images of 39 RCHs (46.4%) and ...

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    9. Retinal Features in Cynomolgus Macaques (Macaca fascicularis) Assessed by Using Scanning Laser Ophthalmoscopy and Spectral Domain Optical Coherence Tomography

      Retinal Features in Cynomolgus Macaques (Macaca fascicularis) Assessed by Using Scanning Laser Ophthalmoscopy and Spectral Domain Optical Coherence Tomography

      Cynomolgus macaques are an important and commonly used species in preclinical toxicology studies, but structural reports of in vivo retinal findings are rare in this species. The purpose of this study was to diminish this gap and document optical coherence tomography and scanning laser ophthalmoscopy imaging data in the healthy posterior pole of cynomolgus monkeys’ eyes at predose examinations. The current study is a retrospective assessment of baseline spectral domain OCT data obtained from the 768 eyes of 384 cynomolgus monkeys (192 males and 192 females) of Mauritian origin. The data set was obtained from studies conducted over a 4-y ...

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    10. Novel biomarker of sphericity and cylindricity indices in volume-rendering optical coherence tomography angiography in normal and diabetic eyes: a preliminary study

      Novel biomarker of sphericity and cylindricity indices in volume-rendering optical coherence tomography angiography in normal and diabetic eyes: a preliminary study

      Purpose Preliminary to evaluate geometric indices (vessel sphericity and cylindricity) for volume-rendered optical coherence tomography angiography (OCTA) in healthy and diabetic eyes. Methods Twenty-six eyes of 13 healthy subjects and 12 eyes of patients with central ischemic, non-proliferative diabetic retinopathy were included. OCTA volume and surface area of the foveal vessels were measured and compared to determine OCTA sphericity and cylindricity indices and surface efficiency (SE). Results The overall average OCTA volume in healthy was 0.49 ± 0.09 mm 3 (standard deviation [SD]), compared to 0.44 ± 0.07 mm 3 (SD) in the diabetic eyes (difference in means ...

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    11. Validation of automated artificial intelligence segmentation of optical coherence tomography images

      Validation of automated artificial intelligence segmentation of optical coherence tomography images

      Purpose To benchmark the human and machine performance of spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) image segmentation, i.e., pixel-wise classification, for the compartments vitreous, retina, choroid, sclera. Methods A convolutional neural network (CNN) was trained on OCT B-scan images annotated by a senior ground truth expert retina specialist to segment the posterior eye compartments. Independent benchmark data sets (30 SDOCT and 30 SSOCT) were manually segmented by three classes of graders with varying levels of ophthalmic proficiencies. Nine graders contributed to benchmark an additional 60 images in three consecutive runs. Inter-human and intra-human class agreement was ...

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    12. High-Performance Virtual Reality Volume Rendering of Original Optical Coherence Tomography Point-Cloud Data Enhanced With Real-Time Ray Casting

      High-Performance Virtual Reality Volume Rendering of Original Optical Coherence Tomography Point-Cloud Data Enhanced With Real-Time Ray Casting

      Purpose : Feasibility testing of a novel volume renders technology to display optical coherence tomography data (OCT) in a virtual reality (VR) environment. Methods : A VR program was written in C++/OpenGL to import and display volumetric OCT data in real time with 180 frames per second using a high-end computer and a tethered head-mounted display. Following exposure, participants completed a Simulator Sickness Questionnaire (SSQ) to assess for nausea, disorientation, and oculomotor disturbances. A user evaluation study of this software was conducted to explore the potential utility of this application. Results : Fifty-seven subjects completed the user testing (34 males and 23 ...

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    1-14 of 14
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    Enhanced resolution and speckle-free three-dimensional printing of macular optical coherence tomography angiography 3D printing of the choroidal vessels and tumours based on optical coherence tomography High-Performance Virtual Reality Volume Rendering of Original Optical Coherence Tomography Point-Cloud Data Enhanced With Real-Time Ray Casting Validation of automated artificial intelligence segmentation of optical coherence tomography images Novel biomarker of sphericity and cylindricity indices in volume-rendering optical coherence tomography angiography in normal and diabetic eyes: a preliminary study Retinal Features in Cynomolgus Macaques (Macaca fascicularis) Assessed by Using Scanning Laser Ophthalmoscopy and Spectral Domain Optical Coherence Tomography Comparison of Current Optical Coherence Tomography Angiography Methods in Imaging Retinal Hemangioblastomas A 3D model to evaluate retinal nerve fiber layer thickness deviations caused by the displacement of optical coherence tomography circular scans in cynomolgus monkeys (Macaca fascicularis) Negative Vessel Remodeling in Stargardt Disease Quantified with Volume-Rendered Optical Coherence Tomography Angiography Unraveling the deep learning gearbox in optical coherence tomography image segmentation towards explainable artificial intelligence Optical coherence tomography findings in patients with transfusion-dependent β-thalassemia Higher-order regression three-dimensional motion-compensation method for real-time optical coherence tomography volumetric imaging of the cornea