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Saeed A, Hadoux X, van Wijngaarden P. Hyperspectral retinal imaging biomarkers of ocular and systemic diseases. Eye (Lond) 2024:10.1038/s41433-024-03135-9. [PMID: 38778136 DOI: 10.1038/s41433-024-03135-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 02/20/2024] [Accepted: 05/07/2024] [Indexed: 05/25/2024] Open
Abstract
Hyperspectral imaging is a frontier in the field of medical imaging technology. It enables the simultaneous collection of spectroscopic and spatial data. Structural and physiological information encoded in these data can be used to identify and localise typically elusive biomarkers. Studies of retinal hyperspectral imaging have provided novel insights into disease pathophysiology and new ways of non-invasive diagnosis and monitoring of retinal and systemic diseases. This review provides a concise overview of recent advances in retinal hyperspectral imaging.
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Affiliation(s)
- Abera Saeed
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, 3002, VIC, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, 3002, VIC, Australia
| | - Xavier Hadoux
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, 3002, VIC, Australia
| | - Peter van Wijngaarden
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, 3002, VIC, Australia.
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, 3002, VIC, Australia.
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2
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Sommer F, Sun B, Fischer J, Goldammer M, Thiele C, Malberg H, Markgraf W. Hyperspectral Imaging during Normothermic Machine Perfusion—A Functional Classification of Ex Vivo Kidneys Based on Convolutional Neural Networks. Biomedicines 2022; 10:biomedicines10020397. [PMID: 35203605 PMCID: PMC8962340 DOI: 10.3390/biomedicines10020397] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 01/28/2022] [Accepted: 01/30/2022] [Indexed: 12/18/2022] Open
Abstract
Facing an ongoing organ shortage in transplant medicine, strategies to increase the use of organs from marginal donors by objective organ assessment are being fostered. In this context, normothermic machine perfusion provides a platform for ex vivo organ evaluation during preservation. Consequently, analytical tools are emerging to determine organ quality. In this study, hyperspectral imaging (HSI) in the wavelength range of 550–995 nm was applied. Classification of 26 kidneys based on HSI was established using KidneyResNet, a convolutional neural network (CNN) based on the ResNet-18 architecture, to predict inulin clearance behavior. HSI preprocessing steps were implemented, including automated region of interest (ROI) selection, before executing the KidneyResNet algorithm. Training parameters and augmentation methods were investigated concerning their influence on the prediction. When classifying individual ROIs, the optimized KidneyResNet model achieved 84% and 62% accuracy in the validation and test set, respectively. With a majority decision on all ROIs of a kidney, the accuracy increased to 96% (validation set) and 100% (test set). These results demonstrate the feasibility of HSI in combination with KidneyResNet for non-invasive prediction of ex vivo kidney function. This knowledge of preoperative renal quality may support the organ acceptance decision.
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Beach JM, Rizvi M, Lichtenfels CB, Vince R, More SS. Topical Review: Studies of Ocular Function and Disease Using Hyperspectral Imaging. Optom Vis Sci 2022; 99:101-113. [PMID: 34897230 DOI: 10.1097/opx.0000000000001853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
SIGNIFICANCE Advances in imaging technology over the last two decades have produced significant innovations in medical imaging. Hyperspectral imaging (HSI) is one of these innovations, enabling powerful new imaging tools for clinical use and greater understanding of tissue optical properties and mechanisms underlying eye disease.Hyperspectral imaging is an important and rapidly growing area in medical imaging, making possible the concurrent collection of spectroscopic and spatial information that is usually obtained from separate optical recordings. In this review, we describe several mainstream techniques used in HSI, along with noteworthy advances in optical technology that enabled modern HSI techniques. Presented also are recent applications of HSI for basic and applied eye research, which include a novel method for assessing dry eye syndrome, clinical slit-lamp examination of corneal injury, measurement of blood oxygen saturation in retinal disease, molecular changes in macular degeneration, and detection of early stages of Alzheimer disease. The review also highlights work resulting from integration of HSI with other imaging tools such as optical coherence tomography and autofluorescence microscopy and discusses the adaptation of HSI for clinical work where eye motion is present. Here, we present the background and main findings from each of these reports along with specific references for additional details.
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Affiliation(s)
- James M Beach
- Center for Drug Design, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota
| | - Madeeha Rizvi
- Center for Drug Design, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota
| | - Caitlin B Lichtenfels
- Center for Drug Design, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota
| | - Robert Vince
- Center for Drug Design, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota
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Marino MJ, Gehlbach PL, Rege A, Jiramongkolchai K. Current and novel multi-imaging modalities to assess retinal oxygenation and blood flow. Eye (Lond) 2021; 35:2962-2972. [PMID: 34117399 PMCID: PMC8526664 DOI: 10.1038/s41433-021-01570-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 01/28/2021] [Accepted: 04/20/2021] [Indexed: 02/05/2023] Open
Abstract
Retinal ischemia characterizes the underlying pathology in a multitude of retinal diseases that can ultimately lead to vision loss. A variety of novel imaging modalities have been developed to characterize retinal ischemia by measuring retinal oxygenation and blood flow in-vivo. These technologies offer valuable insight into the earliest pathophysiologic changes within the retina and provide physicians and researchers with new diagnostic and monitoring capabilities. Future retinal imaging technologies with the capability to provide affordable, noninvasive, and comprehensive data on oxygen saturation, vasculature, and blood flow mechanics are needed. This review will highlight current and future trends in multimodal imaging to assess retinal blood flow and oxygenation.
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Affiliation(s)
- Michael J. Marino
- grid.415233.20000 0004 0444 3298Department of Medicine, MedStar Union Memorial Hospital, Baltimore, MD USA
| | - Peter L. Gehlbach
- grid.21107.350000 0001 2171 9311Retina Division, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD USA
| | - Abhishek Rege
- grid.505446.6Vasoptic Medical, Inc., Baltimore, MD USA
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Lemmens S, Van Eijgen J, Van Keer K, Jacob J, Moylett S, De Groef L, Vancraenendonck T, De Boever P, Stalmans I. Hyperspectral Imaging and the Retina: Worth the Wave? Transl Vis Sci Technol 2020; 9:9. [PMID: 32879765 PMCID: PMC7442879 DOI: 10.1167/tvst.9.9.9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
Purpose Hyperspectral imaging is gaining attention in the biomedical field because it generates additional spectral information to study physiological and clinical processes. Several technologies have been described; however an independent, systematic literature overview is lacking, especially in the field of ophthalmology. This investigation is the first to systematically overview scientific literature specifically regarding retinal hyperspectral imaging. Methods A systematic literature review was conducted, in accordance with PRISMA Statement 2009 criteria, in four bibliographic databases: Medline, Embase, Cochrane Database of Systematic Reviews, and Web of Science. Results Fifty-six articles were found that meet the review criteria. A range of techniques was reported: Fourier analysis, liquid crystal tunable filters, tunable laser sources, dual-slit monochromators, dispersive prisms and gratings, computed tomography, fiber optics, and Fabry-Perrot cavity filter covered complementary metal oxide semiconductor. We present a narrative synthesis and summary tables of findings of the included articles, because methodologic heterogeneity and diverse research topics prevented a meta-analysis being conducted. Conclusions Application in ophthalmology is still in its infancy. Most previous experiments have been performed in the field of retinal oximetry, providing valuable information in the diagnosis and monitoring of various ocular diseases. To date, none of these applications have graduated to clinical practice owing to the lack of sufficiently large validation studies. Translational Relevance Given the promising results that smaller studies show for hyperspectral imaging (e.g., in Alzheimer's disease), advanced research in larger validation studies is warranted to determine its true clinical potential.
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Affiliation(s)
- Sophie Lemmens
- University Hospitals UZ Leuven, Department of Ophthalmology, Leuven, Belgium.,KU Leuven, Biomedical Sciences Group, Department of Neurosciences, Research Group Ophthalmology, Leuven, Belgium.,VITO (Flemish Institute for Technological Research), Health Unit, Boeretang, Belgium
| | - Jan Van Eijgen
- University Hospitals UZ Leuven, Department of Ophthalmology, Leuven, Belgium.,KU Leuven, Biomedical Sciences Group, Department of Neurosciences, Research Group Ophthalmology, Leuven, Belgium.,VITO (Flemish Institute for Technological Research), Health Unit, Boeretang, Belgium
| | - Karel Van Keer
- University Hospitals UZ Leuven, Department of Ophthalmology, Leuven, Belgium.,KU Leuven, Biomedical Sciences Group, Department of Neurosciences, Research Group Ophthalmology, Leuven, Belgium
| | - Julie Jacob
- University Hospitals UZ Leuven, Department of Ophthalmology, Leuven, Belgium.,KU Leuven, Biomedical Sciences Group, Department of Neurosciences, Research Group Ophthalmology, Leuven, Belgium
| | - Sinéad Moylett
- Department of Psychiatry, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
| | - Lies De Groef
- Neural Circuit Development and Regeneration Research Group, Department of Biology, KU Leuven, Leuven, Belgium
| | - Toon Vancraenendonck
- VITO (Flemish Institute for Technological Research), Health Unit, Boeretang, Belgium
| | - Patrick De Boever
- VITO (Flemish Institute for Technological Research), Health Unit, Boeretang, Belgium.,Hasselt University, Centre of Environmental Sciences, Agoralaan, Belgium
| | - Ingeborg Stalmans
- University Hospitals UZ Leuven, Department of Ophthalmology, Leuven, Belgium.,KU Leuven, Biomedical Sciences Group, Department of Neurosciences, Research Group Ophthalmology, Leuven, Belgium
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Markgraf W, Feistel P, Thiele C, Malberg H. Algorithms for mapping kidney tissue oxygenation during normothermic machine perfusion using hyperspectral imaging. ACTA ACUST UNITED AC 2019; 63:557-566. [PMID: 30218598 DOI: 10.1515/bmt-2017-0216] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 09/04/2018] [Indexed: 12/23/2022]
Abstract
The lack of donor grafts is a severe problem in transplantation medicine. Hence, the improved preservation of existing and the usage of organs that were deemed untransplantable is as urgent as ever. The development of novel preservation techniques has come into focus. A promising alternative to traditional cold storage is normothermic machine perfusion (NMP), which provides the benefit of improving the organs' viability and of assessing the organs' status under physiological conditions. For this purpose, methods for evaluating organ parameters have yet to be developed. In a previous study, we determined the tissue oxygen saturation (StO2) of kidneys during NMP with hyperspectral imaging (HSI) based on a discrete wavelength (DW) algorithm. The aim of the current study was to identify a more accurate algorithm for StO2 calculation. A literature search revealed three candidates to test: a DW algorithm and two full spectral algorithms - area under a curve and partial least square regression (PLSR). After obtaining suitable calibration data to train each algorithm, they were evaluated during NMP. The wavelength range from 590 to 800 nm was found to be appropriate for analyzing StO2 of kidneys during NMP. The PLSR method shows good results in analyzing the tissues' oxygen status in perfusion experiments.
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Affiliation(s)
- Wenke Markgraf
- Institute of Biomedical Engineering, Technische Universität Dresden, 01307 Dresden, Germany, Phone: +49 351 463-33392, Fax: +49 351 463-36026
| | - Philipp Feistel
- Institute of Biomedical Engineering, Technische Universität Dresden, 01307 Dresden, Germany
| | - Christine Thiele
- Institute of Biomedical Engineering, Technische Universität Dresden, 01307 Dresden, Germany
| | - Hagen Malberg
- Institute of Biomedical Engineering, Technische Universität Dresden, 01307 Dresden, Germany
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Damodaran M, Amelink A, de Boer JF. Optimal wavelengths for subdiffuse scanning laser oximetry of the human retina. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-15. [PMID: 30152203 DOI: 10.1117/1.jbo.23.8.086003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/02/2018] [Indexed: 06/08/2023]
Abstract
Retinal blood vessel oxygenation is considered to be an important marker for numerous eye diseases. Oxygenation is typically assessed by imaging the retinal vessels at different wavelengths using multispectral imaging techniques, where the choice of wavelengths will affect the achievable measurement accuracy. Here, we present a detailed analysis of the error propagation of measurement noise in retinal oximetry, to identify optimal wavelengths that will yield the lowest uncertainty in saturation estimation for a given measurement noise level. In our analysis, we also investigate the effect of hemoglobin packing in discrete blood vessels (pigment packaging), which may result in a nonnegligible bias in saturation estimation if unaccounted for under specific geometrical conditions, such as subdiffuse sampling of smaller blood vessels located deeper within the retina. Our analyses show that using 470, 506, and 592 nm, a fairly accurate estimation of the whole oxygen saturation regime [0 1] can be realized, even in the presence of the pigment packing effect. To validate the analysis, we developed a scanning laser ophthalmoscope to produce high contrast images with a maximum pixel rate of 60 kHz and a maximum 30-deg imaging field of view. Confocal reflectance measurements were then conducted on a tissue-mimicking scattering phantom with optical properties similar to retinal tissue including narrow channels filled with absorbing dyes to mimic blood vessels. By imaging at three optimal wavelengths, the saturation of the dye combination was calculated. The experimental values show good agreement with our theoretical derivations.
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Affiliation(s)
- Mathi Damodaran
- Vrije Universiteit Amsterdam, LaserLaB, Department of Physics and Astronomy, Amsterdam, The Netherlands
| | - Arjen Amelink
- Netherlands Organisation for Applied Scientific Research TNO, Department of Optics, Delft, The Netherlands
| | - Johannes F de Boer
- Vrije Universiteit Amsterdam, LaserLaB, Department of Physics and Astronomy, Amsterdam, The Netherlands
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8
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Yap ZL, Verma S, Lee YF, Ong C, Mohla A, Perera SA. Glaucoma related retinal oximetry: a technology update. Clin Ophthalmol 2018; 12:79-84. [PMID: 29379268 PMCID: PMC5757969 DOI: 10.2147/opth.s128459] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
There are two long-standing theories about the pathogenesis of glaucoma – barotrauma and the effect of vascular hypoxia. Currently, it is still unknown whether diminished blood flow is the cause or result of glaucomatous atrophy of ganglion cells and the optic nerve. Though many other imaging techniques used to directly assess ocular blood flow have been well studied, they are limited by their inability to directly assess metabolism in the ocular tissues or measure the oxygen carrying capacity in the vessels. Retinal oximetry is a relatively novel, noninvasive imaging technique that reliably measures oxygen saturation levels in the retinal vessels, offering surrogate markers for the metabolic demands of the eye. The clinical significance of these measurements has not been well established. Thus, this review gives an overview of ocular imaging and current retinal oximetry techniques, while contextualizing the important oximetry studies that have investigated the vascular theory behind glaucoma.
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Affiliation(s)
- Zhu Li Yap
- Singapore National Eye Center.,Singapore Eye Research Institute, Singapore
| | | | - Yi Fang Lee
- Singapore National Eye Center.,Singapore Eye Research Institute, Singapore
| | - Charles Ong
- Singapore National Eye Center.,Singapore Eye Research Institute, Singapore
| | - Aditi Mohla
- Singapore National Eye Center.,Singapore Eye Research Institute, Singapore
| | - Shamira A Perera
- Singapore National Eye Center.,Singapore Eye Research Institute, Singapore
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Desjardins M, Sylvestre JP, Jafari R, Kulasekara S, Rose K, Trussart R, Arbour JD, Hudson C, Lesage F. Preliminary investigation of multispectral retinal tissue oximetry mapping using a hyperspectral retinal camera. Exp Eye Res 2016; 146:330-340. [PMID: 27060375 DOI: 10.1016/j.exer.2016.04.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 03/31/2016] [Accepted: 04/01/2016] [Indexed: 10/22/2022]
Abstract
Oximetry measurement of principal retinal vessels represents a first step towards understanding retinal metabolism, but the technique could be significantly enhanced by spectral imaging of the fundus outside of main vessels. In this study, a recently developed Hyperspectral Retinal Camera was used to measure relative oximetric (SatO2) and total hemoglobin (HbT) maps of the retina, outside of large vessels, in healthy volunteers at baseline (N = 7) and during systemic hypoxia (N = 11), as well as in patients with glaucoma (N = 2). Images of the retina, on a field of view of ∼30°, were acquired between 500 and 600 nm with 2 and 5 nm steps, in under 3 s. The reflectance spectrum from each pixel was fitted to a model having oxy- and deoxyhemoglobin as the main absorbers and scattering modeled by a power law, yielding estimates of relative SatO2 and HbT over the fundus. Average optic nerve head (ONH) saturation over 8 eyes was 68 ± 5%. During systemic hypoxia, mean ONH saturation decreased by 12.5% on average. Upon further development and validation, the relative SatO2 and HbT maps of microvasculature obtained with this imaging system could ultimately contribute to the diagnostic and management of diseases affecting the ONH and retina.
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Affiliation(s)
- Michèle Desjardins
- École Polytechnique de Montréal, Institut de génie biomédical, Département de Génie électrique, 2900, boul. Édouard-Montpetit, Montréal, Qc, H3T 1J4, Canada.
| | | | - Reza Jafari
- Optina Diagnostics, 3900 boul. Cote-Vertu, Suite #220, St-Laurent, Qc, H4R 1V4, Canada
| | - Susith Kulasekara
- University of Toronto, Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, 399 Bathurst Street, Toronto, On, M5T 2S8, Canada
| | - Kalpana Rose
- University of Toronto, Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, 399 Bathurst Street, Toronto, On, M5T 2S8, Canada
| | - Rachel Trussart
- Université de Montréal, Département d'ophtalmologie, 2900 Boulevard Édouard-Montpetit, Montréal, Qc, H3T 1J4, Canada
| | - Jean Daniel Arbour
- Université de Montréal, Département d'ophtalmologie, 2900 Boulevard Édouard-Montpetit, Montréal, Qc, H3T 1J4, Canada
| | - Chris Hudson
- University of Toronto, Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, 399 Bathurst Street, Toronto, On, M5T 2S8, Canada; University of Waterloo, School of Optometry and Vision Science, 200 University Ave W, Waterloo, On, N2L 3G1, Canada
| | - Frédéric Lesage
- École Polytechnique de Montréal, Institut de génie biomédical, Département de Génie électrique, 2900, boul. Édouard-Montpetit, Montréal, Qc, H3T 1J4, Canada.
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Radrich K, Ntziachristos V. Quantitative multi-spectral oxygen saturation measurements independent of tissue optical properties. JOURNAL OF BIOPHOTONICS 2016; 9:83-99. [PMID: 25765987 DOI: 10.1002/jbio.201400092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 10/19/2014] [Accepted: 01/26/2015] [Indexed: 06/04/2023]
Abstract
Imaging of tissue oxygenation is important in several applications associated with patient care. Optical sensing is commonly applied for assessing oxygen saturation but is often restricted to local measurements or else it requires spectral and spatial information at the expense of time. Many methods proposed so far require assumptions on the properties of measured tissue. In this study we investigated a computational method that uses only multispectral information and quantitatively computes tissue oxygen saturation independently of tissue optical properties. The method is based on linear transformations of measurements in three isosbestic points. We investigated the ideal isosbestic point combination out of six isosbestic points available for measurement in the visible and near-infrared region that enable accurate oxygen saturation computation. We demonstrate this method on controlled tissue mimicking phantoms having different optical properties and validated the measurements using a gas analyzer. A mean error of 2.9 ± 2.8% O2 Sat was achieved. Finally, we performed pilot studies in tissues in-vivo by measuring dynamic changes in fingers subjected to vascular occlusion, the vasculature of mouse ears and exposed mouse organs.
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Affiliation(s)
- Karin Radrich
- Technische Universität München, Chair for Biological Imaging, Munich, Germany
- Helmholtz Zentrum München, Institute for Biological and Medical Imaging, Neuherberg, Germany
| | - Vasilis Ntziachristos
- Technische Universität München, Chair for Biological Imaging, Munich, Germany
- Helmholtz Zentrum München, Institute for Biological and Medical Imaging, Neuherberg, Germany
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11
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Klefter ON, Lauritsen AØ, Larsen M. Retinal hemodynamic oxygen reactivity assessed by perfusion velocity, blood oximetry and vessel diameter measurements. Acta Ophthalmol 2015; 93:232-41. [PMID: 25270587 DOI: 10.1111/aos.12553] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 08/05/2014] [Indexed: 01/02/2023]
Abstract
PURPOSE To test the oxygen reactivity of a fundus photographic method of measuring macular perfusion velocity and to integrate macular perfusion velocities with measurements of retinal vessel diameters and blood oxygen saturation. METHODS Sixteen eyes in 16 healthy volunteers were studied at two examination sessions using motion-contrast velocimetry and retinal oximetry with vessel diameter corrections. To test oxygen reactivity, participants were examined during normoxia, after 15 min of hyperoxia and finally after 45 min of normoxia. Repeatability was assessed by intraclass correlation coefficients (ICC) and limits of agreement. RESULTS Fifteen minutes of hyperoxia was accompanied by mean reductions in arterial and venous perfusion velocities of 14% and 16%, respectively (p = 0.0080; p = 0.0019), constriction of major arteries and veins by 5.5% and 8.2%, respectively (p < 0.0001), increased retinal arterial oxygen saturation from 95.1 ± 5.0% to 96.6 ± 6.4% (p = 0.038) and increased retinal venous oxygen saturation from 62.9 ± 6.7% to 70.3 ± 7.8% (p = 0.0010). Parameters returned to baseline levels after subsequent normoxia. Saturation and vessel diameter ICCs were 0.88-0.98 (range). For perfusion velocities, short-term ICCs were 0.79-0.82 and long-term ICCs were 0.06-0.11. Intersession increases in blood glucose were associated with reductions in perfusion velocities (arterial p = 0.0067; venous p = 0.018). CONCLUSION Oxygen reactivity testing supported that motion-contrast velocimetry is a valid method for assessing macular perfusion. Results were consistent with previous observations of hyperoxic blood flow reduction using blue field entoptic and laser Doppler velocimetry. Retinal perfusion seemed to be regulated around individual set points according to blood glucose levels. Multimodal measurements may provide comprehensive information about retinal metabolism.
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Affiliation(s)
- Oliver Niels Klefter
- Department of Ophthalmology Glostrup Hospital Glostrup Denmark
- Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | | | - Michael Larsen
- Department of Ophthalmology Glostrup Hospital Glostrup Denmark
- Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
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12
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Ibrahim MA, Annam RE, Sepah YJ, Luu L, Bittencourt MG, Jang HS, Lemaillet P, Munoz B, Duncan DD, West S, Nguyen QD, Ramella-Roman JC. Assessment of oxygen saturation in retinal vessels of normal subjects and diabetic patients with and without retinopathy using Flow Oximetry System. Quant Imaging Med Surg 2015; 5:86-96. [PMID: 25694958 DOI: 10.3978/j.issn.2223-4292.2014.11.26] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 10/31/2014] [Indexed: 12/11/2022]
Abstract
PURPOSE To assess oxygen saturation (StO2) in retinal vessels of normal subjects and diabetic patients with and without retinopathy using the modified version of the Flow Oximetry System (FOS) and a novel assessment software. METHODS The FOS and novel assessment software were used to determine StO2 levels in arteries and veins located between 1 and 2 mm from the margin of the optic disc and in the macular area. RESULTS Eighteen normal subjects, 15 diabetics without diabetic retinopathy (DM no DR), and 11 with non-proliferative diabetic retinopathy (NPDR) were included in final analysis. The mean [± standard deviation (SD)] StO2 in retinal arteries was 96.9%±3.8% in normal subjects; 97.4%±3.7% in DM no DR; and 98.4%±2.0% in NPDR. The mean venous StO2 was 57.5%±6.8% in normal subjects; 57.4%±7.5% in DM no DR; and 51.8%±6.8% in NPDR. The mean arterial and venous StO2 across the three groups were not statistically different (P=0.498 and P=0.071, respectively). The arterio-venous differences between the three study groups, however, were found to be statistically significant (P=0.015). Pairwise comparisons have demonstrated significant differences when comparing the A-V difference in the NPDR group to either normal subjects (P=0.02) or diabetic patients without DR (P=0.04). CONCLUSIONS The arterio-venous difference was greater, and statistically significant, in patients with NPDR when compared to normal subjects and to patients with diabetes and no retinopathy. The mean venous StO2 was lower, but not statistically significant, in NPDR compared with diabetics without retinopathy and with normal subjects.
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Affiliation(s)
- Mohamed A Ibrahim
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Rachel E Annam
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Yasir J Sepah
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Long Luu
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Millena G Bittencourt
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Hyun S Jang
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Paul Lemaillet
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Beatriz Munoz
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Donald D Duncan
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Sheila West
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Quan Dong Nguyen
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Jessica C Ramella-Roman
- 1 Retinal Imaging Research and Reading Center (RIRRC), Wilmer Eye Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA ; 2 Ocular Imaging Research and Reading Center (OIRRC), Stanley M. Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA ; 3 Department of Biomedical Engineering, The Catholic University of America, Washington, DC, USA ; 4 Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, USA ; 5 Department of Electrical and Computer Engineering, Portland State University, Oregon, USA ; 6 Department of Biomedical Engineering, and Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
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O'Connell RA, Anderson AJ, Hosking SL, Bui BV. Provocative intraocular pressure challenge preferentially decreases venous oxygen saturation despite no reduction in blood flow. Ophthalmic Physiol Opt 2014; 35:114-24. [PMID: 25528886 DOI: 10.1111/opo.12170] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 10/17/2014] [Indexed: 01/27/2023]
Abstract
PURPOSE Ocular disease can both alter the retina's oxygen requirements, and decrease its ability to cope with changes in metabolic demand. We examined the influence of a moderate intraocular pressure (IOP) elevation on three outcome measures: arterial and venous oxygen saturation, blood flow, and the pattern electroretinogram (PERG). METHODS We increased IOP to ˜30 mmHg in 23 healthy participants (22-39 years) using a mechanical probe applied to the eyelid, thereby lowering ocular perfusion pressure (OPP) by ~30%. The Oxymap retinal oximeter was used to measure oxygen saturation for arteries and veins. Blood flow, volume and velocity were measured using the Heidelberg retinal flowmeter and steady-state PERG waveforms (8.34 Hz) were recorded bilaterally (200 sweeps). For each outcome measure, data was obtained three times: at baseline, 1 min into sustained IOP elevation, and 1 min after the probe was removed. RESULTS During IOP elevation, changes in oxygen saturation of retinal arteries failed to reach statistical significance [F(1,30) = 3.69, p = 0.05], whereas venous oxygen saturation was significantly reduced [F(1,21) = 27.43, p < 0.01]. Blood flow increased slightly [F(2,40) = 6.28, p < 0.0001], PERG amplitude significantly reduced [F(2,44) = 24.24, p < 0.0001] and PERG phase was significantly delayed [F(2,44) = 17.00, p < 0.0001]. Contralateral eyes were unchanged. OPP reduction correlated little with PERG amplitude, PERG phase or venous oxygen saturation. CONCLUSIONS Mild, acute IOP elevation increases arterio-venous oxygen saturation differences primarily through lowering venous oxygen saturation, suggesting increased oxygen consumption by healthy neurons when physiologically stressed.
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Affiliation(s)
- Rachael A O'Connell
- Department of Optometry and Vision Sciences, The University of Melbourne, Melbourne, Australia; Department of Ophthalmology, Countess of Chester Hospital NHS Foundation Trust, Chester, UK
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Gramatikov BI. Modern technologies for retinal scanning and imaging: an introduction for the biomedical engineer. Biomed Eng Online 2014; 13:52. [PMID: 24779618 PMCID: PMC4022984 DOI: 10.1186/1475-925x-13-52] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 04/11/2014] [Indexed: 12/17/2022] Open
Abstract
This review article is meant to help biomedical engineers and nonphysical scientists better understand the principles of, and the main trends in modern scanning and imaging modalities used in ophthalmology. It is intended to ease the communication between physicists, medical doctors and engineers, and hopefully encourage “classical” biomedical engineers to generate new ideas and to initiate projects in an area which has traditionally been dominated by optical physics. Most of the methods involved are applicable to other areas of biomedical optics and optoelectronics, such as microscopic imaging, spectroscopy, spectral imaging, opto-acoustic tomography, fluorescence imaging etc., all of which are with potential biomedical application. Although all described methods are novel and important, the emphasis of this review has been placed on three technologies introduced in the 1990’s and still undergoing vigorous development: Confocal Scanning Laser Ophthalmoscopy, Optical Coherence Tomography, and polarization-sensitive retinal scanning.
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Affiliation(s)
- Boris I Gramatikov
- Laboratory of Ophthalmic Optics, Wilmer Eye Institute, Johns Hopkins University School of Medicine, 600 N, Wolfe St,, Baltimore MD 21287, USA.
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Shahidi A, Patel S, Flanagan J, Hudson C. Regional variation in human retinal vessel oxygen saturation. Exp Eye Res 2013; 113:143-7. [DOI: 10.1016/j.exer.2013.06.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 05/29/2013] [Accepted: 06/03/2013] [Indexed: 11/29/2022]
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Abstract
UNLABELLED ABSTRACT.: PURPOSE Malfunction of retinal blood flow or oxygenation is believed to be involved in various diseases. Among them are retinal vessel occlusions, diabetic retinopathy and glaucoma. Reliable, non-invasive technology for retinal oxygen measurements has been scarce and most of the knowledge on retinal oxygenation comes from animal studies. This thesis describes human retinal oximetry, performed with novel retinal oximetry technology. The thesis describes studies on retinal vessel oxygen saturation in (1) light and dark in healthy volunteers, (2) central retinal vein occlusion, (3) branch retinal vein occlusion, (4) central retinal artery occlusion, (5) diabetic retinopathy, (6) patients undergoing glaucoma surgery and (7) patients taking glaucoma medication. METHODS The retinal oximeter (Oxymap ehf., Reykjavik, Iceland) is based on a fundus camera. An attached image splitter allows the simultaneous capture of four images of the same area of the fundus. Two images are used for further analysis, one acquired with 586 nm light and one with 605 nm light. Light absorbance of retinal vessels is sensitive to oxygen saturation at 605 nm but not at 586 nm. Measurement of reflected light at these wavelengths allows estimation of oxygen saturation in the main retinal vessels. This is performed with custom-made analysis software. RESULTS LIGHT AND DARK: After 30 min in the dark, oxygen saturation in retinal arterioles of healthy volunteers was 92 ± 4% (mean ± SD, n = 15). After 5 min in 80 cd/m(2) light, the arteriolar saturation was 89 ± 5%. The decrease was statistically significant (p = 0.008). The corresponding values for retinal venules were 60 ± 5% in the dark and 55 ± 10% in the light (p = 0.020). Similar results were found after alternating 5 min periods of darkness and light. In a second experiment (n = 19), a significant decrease in retinal vessel oxygen saturation was found in 100 cd/m(2) light compared with darkness but 1 and 10 cd/m(2) light had no significant effect. CENTRAL RETINAL VEIN OCCLUSION: In patients with central retinal vein occlusion, the mean saturation in affected retinal venules was 49 ± 12%, while the mean value for venules in the fellow eye was 65 ± 6% (mean ± SD, p = 0.003, n = 8). The retinal arteriolar saturation was the same in affected (99 ± 3%) and the unaffected (99 ± 6%) eyes. The venous oxygen saturation showed much variation between affected eyes. BRANCH RETINAL VEIN OCCLUSION: Median oxygen saturation in venules affected by branch retinal vein occlusion was 59% (range, 12-93%, n = 22), while it was 63% (23-80%) in unaffected venules in the affected eye and 55% (39-80%) in venules in the fellow eye. The difference was not statistically significant (p > 0.05). There was a significant difference between affected arterioles (median 101%; range, 89-115%) and unaffected arterioles (95%, 85-104%) in the affected eye (p < 0.05, n = 18). CENTRAL RETINAL ARTERY OCCLUSION: In a patient with a day's history of central retinal artery occlusion due to temporal arteritis, the mean arteriolar saturation was 71 ± 9% and 63 ± 9% in the venules. One month later, after treatment with prednisolone, the mean arteriolar saturation was 100 ± 4% and the venous saturation 54 ± 5%. DIABETIC RETINOPATHY: When compared with healthy volunteers (n = 31), patients with all categories of diabetic retinopathy had on average 7-10 percentage points higher saturation in retinal arterioles (p < 0.05 for all categories, n = 6-8 in each category). In venules, the saturation was 8-12 percentage points higher (p < 0.05 for all categories). GLAUCOMA SURGERY: Oxygen saturation in retinal arterioles increased by 2 percentage points on average (p = 0.046, n = 19) with surgery, which lowered intraocular pressure from 23 ± 7 mmHg (mean ± SD) to 10 ± 4 mmHg (p < 0.0001). No other significant changes were found (p ≥ 0.35). DORZOLAMIDE: A significant reduction of 3 percentage points was found in arterioles (p < 0.01) and venules (p < 0.05) when patients with glaucoma or ocular hypertension changed from dorzolamide-timolol combination eye drops to timolol alone (n = 6). No change was found in patients, who started on timolol and switched to the combination therapy (p > 0.05, n = 7). CONCLUSIONS Dual wavelength oximetry can be used to non-invasively measure retinal vessel oxygen saturation in health and disease. The results indicate that retinal vessel oxygen saturation is (1) increased in the dark, (2) lower in venules affected by central retinal vein occlusions, (3) variable in branch retinal vein occlusion, (4) lower in retinal arterioles in central retinal artery occlusion, (5) increased in diabetic retinopathy, (6-7) mildly affected by glaucoma surgery or dorzolamide.
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Gao L, Smith RT, Tkaczyk TS. Snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS). BIOMEDICAL OPTICS EXPRESS 2012; 3:48-54. [PMID: 22254167 PMCID: PMC3255341 DOI: 10.1364/boe.3.000048] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 11/30/2011] [Accepted: 12/02/2011] [Indexed: 05/04/2023]
Abstract
We present a snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS) for eye imaging applications. The resulting system is capable of simultaneously acquiring 48 spectral channel images in the range 470 nm-650 nm with frame rate at 5.2 fps. The spatial sampling of each measured spectral scene is 350 × 350 pixels. The advantages of this snapshot device are elimination of the eye motion artifacts and pixel misregistration problems in traditional scanning-based hyperspectral retinal cameras, and real-time imaging of oxygen saturation dynamics with sub-second temporal resolution. The spectral imaging performance is demonstrated in a human retinal imaging experiment in vivo. The absorption spectral signatures of oxy-hemoglobin and macular pigments were successfully acquired by using this device.
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Affiliation(s)
- Liang Gao
- Department of Bioengineering, Rice University, 6100 Main Street, MS 142, Houston, TX 77005, USA
| | - R. Theodore Smith
- Harkness Eye Institute, Department of Ophthalmology, Columbia University, 635 West 165 St., New York, NY 10032, USA
| | - Tomasz S. Tkaczyk
- Department of Bioengineering, Rice University, 6100 Main Street, MS 142, Houston, TX 77005, USA
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, MS 142, Houston, TX 77005, USA
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Denniss J, Schiessl I, Nourrit V, Fenerty CH, Gautam R, Henson DB. Relationships between visual field sensitivity and spectral absorption properties of the neuroretinal rim in glaucoma by multispectral imaging. Invest Ophthalmol Vis Sci 2011; 52:8732-8. [PMID: 21980002 DOI: 10.1167/iovs.11-8302] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Abstract
PURPOSE To investigate the relationship between neuroretinal rim (NRR) differential light absorption (DLA, a measure of spectral absorption properties) and visual field (VF) sensitivity in primary open-angle glaucoma (POAG). METHODS Patients diagnosed with (n = 22) or suspected of having (n = 7) POAG were imaged with a multispectral system incorporating a modified digital fundus camera, 250-W tungsten-halogen lamp, and fast-tuneable liquid crystal filter. Five images were captured sequentially within 1.0 second at wavelengths selected according to absorption properties of hemoglobin (range, 570-610 nm), and a Beer-Lambert law model was used to produce DLA maps of residual NRR from the images. Patients also underwent VF testing. Differences in NRR DLA in vertically opposing 180° and 45° sectors either side of the horizontal midline were compared with corresponding differences in VF sensitivity on both decibel and linear scales by Spearman's rank correlation. RESULTS The decibel VF sensitivity scale showed significant relationships between superior-inferior NRR DLA difference and sensitivity differences between corresponding VF areas in 180° NRR sectors (Spearman ρ = 0.68; P < 0.0001), superior-/inferior-temporal 45° NRR sectors (ρ = 0.57; P < 0.002), and superior-/inferior-nasal 45° NRR sectors (ρ = 0.59; P < 0.001). Using the linear VF sensitivity scale significant relationships were found for 180° NRR sectors (ρ = 0.62; P < 0.0002) and superior-inferior-nasal 45° NRR sectors (ρ = 0.53; P < 0.002). No significant difference was found between correlations using the linear or decibel VF sensitivity scales. CONCLUSIONS Residual NRR DLA is related to VF sensitivity in POAG. Multispectral imaging may provide clinically important information for the assessment and management of POAG.
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Affiliation(s)
- Jonathan Denniss
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
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Nourrit V, Denniss J, Muqit M, Schiessl I, Fenerty C, Stanga P, Henson D. High-resolution hyperspectral imaging of the retina with a modified fundus camera. J Fr Ophtalmol 2010; 33:686-92. [DOI: 10.1016/j.jfo.2010.10.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Accepted: 09/28/2010] [Indexed: 10/18/2022]
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Shahidi M, Wanek J, Blair NP, Mori M. Three-dimensional mapping of chorioretinal vascular oxygen tension in the rat. Invest Ophthalmol Vis Sci 2008; 50:820-5. [PMID: 18824736 DOI: 10.1167/iovs.08-2343] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE An optical section phosphorescence lifetime imaging system was developed for three-dimensional mapping of oxygen tension (P(O2)) in chorioretinal vasculatures. METHODS A laser line was projected at an oblique angle and scanned on the retina after intravenous injection of an oxygen-sensitive molecular probe to generate phosphorescence optical section images. An automated software algorithm segmented and combined images from spatially adjacent locations to construct depth-displaced en face retinal images. Intravascular P(O2) was measured by determining the phosphorescence lifetime. Three-dimensional chorioretinal P(O2) maps were generated in rat eyes under varying fractions of inspired oxygen. RESULTS Under an air-breathing condition, mean P(O2) in the choroid, retinal arteries, capillaries, and veins were 58+/-2 mm Hg, 47+/-2 mm Hg, 44+/-2 mm Hg, and 35+/-2 mm Hg, respectively. The mean arteriovenous P(O2) difference was 12+/-2 mm Hg. With a lower fraction of inspired oxygen, chorioretinal vascular P(O2) and mean arteriovenous P(O2) differences decreased compared with measurements under an air-breathing condition. Retinal venous P(O2) was statistically lower than P(O2) measured in the retinal artery, capillaries, and choroid (P<0.004). CONCLUSIONS Three-dimensional mapping of chorioretinal oxygen tension allowed quantitative P(O2) measurements in large retinal blood vessels and in retinal capillaries. This method has the potential to facilitate better understanding of retinal oxygenation in health and disease.
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Affiliation(s)
- Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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