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Hoel S, Moe K, Sugulle M, Petrovski G, Veiby NCBB, Staff AC. Retinal oximetry and microvascular assessment after hypertensive pregnancy complications. Acta Ophthalmol 2024; 102:653-661. [PMID: 38342958 DOI: 10.1111/aos.16651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 12/19/2023] [Accepted: 01/25/2024] [Indexed: 02/13/2024]
Abstract
PURPOSE Women with hypertensive disorders of pregnancy (HDP) are at increased risk of developing premature cardiovascular disease (CVD). The mechanisms behind this are not fully understood, but microvascular alterations have been documented in retinal arterioles and venules. The aim of this study was to use non-invasive retinal imaging to investigate the structural and functional properties of arterioles, venules and capillaries in this patient group. METHODS We examined 27 women with previous HDP and 23 controls at 3 years postpartum. The retinal microvasculature was assessed by vessel calibre measurements, retinal oximetry and optical coherence tomography angiography. Differences were analysed using non-parametric tests and multiple regression analyses, adjusted for age and body mass index. RESULTS Median arteriolar oxygen saturation (SaO2; 94.2% vs. 93.0%), venular oxygen saturation (SvO2; 60.1% vs. 62.4%) and arteriovenous saturation difference (AV-difference; 32.8% vs. 32.3%) were similar across groups. Capillary vessel density (VD; 46.2% vs. 46.3%), skeletonised VD (VSD; 21.3 vs. 21.1 mm/mm2) and vessel diameter index (21.65 vs. 21.86) were also comparable. In the HDP group, mean arterial pressure (MAP) was positively correlated with AV-difference (R2 = 0.209) and negatively correlated with arteriolar diameter (CRAE; r2 = 0.382). CONCLUSIONS Structural microvascular alterations appear not to be key biomarkers for CVD risk after HDP as early as 3 years postpartum in otherwise healthy women. Further studies are needed to evaluate whether such changes occur later in life. MAP was associated with AV-difference only in the HDP group, suggesting specific mechanisms affecting functional microvascular properties in these women.
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Affiliation(s)
- Sissel Hoel
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Division of Obstetrics and Gynaecology, Oslo University Hospital, Oslo, Norway
| | - Kjartan Moe
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Division of Obstetrics and Gynaecology, Oslo University Hospital, Oslo, Norway
| | - Meryam Sugulle
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Division of Obstetrics and Gynaecology, Oslo University Hospital, Oslo, Norway
| | - Goran Petrovski
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Ophthalmology, Center for Eye Research and Innovative Diagnostics, Oslo University Hospital, Oslo, Norway
- Department of Ophthalmology, University of Split School of Medicine and University Hospital Centre, Split, Croatia
- UKLONetwork, University St. Kliment Ohridski-Bitola, Bitola, North Macedonia
| | - Nina Charlotte B B Veiby
- Department of Ophthalmology, Center for Eye Research and Innovative Diagnostics, Oslo University Hospital, Oslo, Norway
| | - Anne Cathrine Staff
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Division of Obstetrics and Gynaecology, Oslo University Hospital, Oslo, Norway
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2
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Guldfeldt MU, Pilegaard FP, Malmqvist L, Klefter ON, Hamann S. Validation of retinal oximetry vessel selection using fluorescein angiography in patients with optic disc drusen. Exp Eye Res 2024; 243:109882. [PMID: 38582182 DOI: 10.1016/j.exer.2024.109882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 04/08/2024]
Abstract
Retinal oximetry could provide insights into the pathophysiology of optic nerve disease, including optic disc drusen (ODD). Vessel selection for oximetry analysis is based on morphological characteristics of arterioles and venules and supported by an overlay of estimated blood oxygen saturations. The purpose of this cross-sectional study was to determine the validity of this vessel selection procedure by comparing it with vessel selection supported by video fluorescein angiography (FA). The study included 36 eyes of 36 patients with ODD who underwent retinal oximetry (Oxymap retinal oximeter T1) followed by FA (Heidelberg Spectralis). Two trained graders selected vessel segments in a pre-defined measurement area around the optic disc. One of these graders additionally performed the vessel segment selection with the support of FA images. When performed by the same grader, FA-supported and non-FA-supported vessel selection did not lead to significant differences in total vessel segment length, estimated oxygen saturations or vessel diameters (all p > 0.05). Inter-grader differences were found for arterial and venous segment lengths and arterial saturation (p < 0.05). A similar tendency was found for the arteriovenous saturation difference (p = 0.10). In conclusion, identifying vessel segments for retinal oximetry analysis based on vessel morphology and supported by a color-coded saturation overlay appears to be a valid method without the need for invasive angiography. A numerically small inter-grader variation may influence oximetry results. Further studies of retinal oximetry in ODD are warranted.
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Affiliation(s)
- Mia Uhre Guldfeldt
- Department of Ophthalmology, Rigshospitalet, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Freja Pind Pilegaard
- Department of Ophthalmology, Rigshospitalet, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Lasse Malmqvist
- Department of Ophthalmology, Rigshospitalet, Copenhagen, Denmark
| | - Oliver Niels Klefter
- Department of Ophthalmology, Rigshospitalet, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Steffen Hamann
- Department of Ophthalmology, Rigshospitalet, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
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Beach JM, Shoemaker B, Eckert GJ, Harris A, Siesky B, Arciero JC. Potential measurement error from vessel reflex and multiple light paths in dual-wavelength retinal oximetry. Acta Ophthalmol 2024; 102:e367-e380. [PMID: 37786359 PMCID: PMC10987395 DOI: 10.1111/aos.15776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 08/15/2023] [Accepted: 09/18/2023] [Indexed: 10/04/2023]
Abstract
PURPOSE This study aims to characterize the dependence of measured retinal arterial and venous saturation on vessel diameter and central reflex in retinal oximetry, with an ultimate goal of identifying potential causes and suggesting approaches to improve measurement accuracy. METHODS In 10 subjects, oxygen saturation, vessel diameter and optical density are obtained using Oxymap Analyzer software without diameter correction. Diameter dependence of saturation is characterized using linear regression between measured values of saturation and diameter. Occurrences of negative values of vessel optical densities (ODs) associated with central vessel reflex are acquired from Oxymap Analyzer. A conceptual model is used to calculate the ratio of optical densities (ODRs) according to retinal reflectance properties and single and double-pass light transmission across fixed path lengths. Model-predicted values are compared with measured oximetry values at different vessel diameters. RESULTS Venous saturation shows an inverse relationship with vessel diameter (D) across subjects, with a mean slope of -0.180 (SE = 0.022) %/μm (20 < D < 180 μm) and a more rapid saturation increase at small vessel diameters reaching to over 80%. Arterial saturation yields smaller positive and negative slopes in individual subjects, with an average of -0.007 (SE = 0.021) %/μm (20 < D < 200 μm) across all subjects. Measurements where vessel brightness exceeds that of the retinal background result in negative values of optical density, causing an artifactual increase in saturation. Optimization of model reflectance values produces a good fit of the conceptual model to measured ODRs. CONCLUSION Measurement artefacts in retinal oximetry are caused by strong central vessel reflections, and apparent diameter sensitivity may result from single and double-pass transmission in vessels. Improvement in correction for vessel diameter is indicated for arteries however further study is necessary for venous corrections.
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Affiliation(s)
| | - Benjamin Shoemaker
- Indiana University - Purdue University Indianapolis (IUPUI), Indianapolis, Indiana, USA
| | - George J Eckert
- Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Alon Harris
- Icahn School of Medicine, Mt. Sinai, New York, USA
| | - Brent Siesky
- Icahn School of Medicine, Mt. Sinai, New York, USA
| | - Julia C Arciero
- Indiana University - Purdue University Indianapolis (IUPUI), Indianapolis, Indiana, USA
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4
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Akitegetse C, Poirier J, Sauvageau D. Sensitivity of visible range multi-wavelength algorithms for retinal tissue oximetry to acquisition parameters. BIOMEDICAL OPTICS EXPRESS 2023; 14:4296-4309. [PMID: 37799705 PMCID: PMC10549742 DOI: 10.1364/boe.495721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/16/2023] [Accepted: 07/18/2023] [Indexed: 10/07/2023]
Abstract
This study examined the sensitivity of broadband spectroscopy algorithms for retinal tissue oximetry to spectral acquisition parameters. Monte Carlo simulations were conducted on a 4-layer retinal model to assess the impact of various parameters. The optimal spectral range for accurate measurements was determined to be 530 nm to 585 nm. Decreased spectral resolution below 4 nm significantly reduced accuracy. Using an acquisition area larger than the blood vessel resulted in an underestimation of oxygen saturation, especially for high values. A threshold was observed where increased light intensity had no significant impact on measurement variability. The study highlights the importance of informed parameter selection for accurately assessing retinal microcapillary oxygenation and studying local hemodynamics.
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Affiliation(s)
| | | | - Dominic Sauvageau
- Zilia inc., Québec, QC, G1K 3G5, Canada
- Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada
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5
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Zhang J, Luo Z, Wang G, Huang Y, Fei K, Liu Y, Li J, Yuan J, Xiao P. Oxygen-saturation-related functional parameter as a biomarker for diabetes mellitus-extraction method and clinical validation. Front Cell Dev Biol 2023; 11:1195873. [PMID: 37250897 PMCID: PMC10213938 DOI: 10.3389/fcell.2023.1195873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 05/02/2023] [Indexed: 05/31/2023] Open
Abstract
Purpose: To develop a computational method for oxygen-saturation-related functional parameter analysis of retinal vessels based on traditional color fundus photography, and to explore their characteristic alterations in type 2 diabetes mellitus (DM). Methods: 50 type 2 DM patients with no-clinically detectable retinopathy (NDR) and 50 healthy subjects were enrolled in the study. An optical density ratio (ODR) extraction algorithm based on the separation of oxygen-sensitive and oxygen-insensitive channels in color fundus photography was proposed. With precise vascular network segmentation and arteriovenous labeling, ODRs were acquired from different vascular subgroups, and the global ODR variability (ODRv) was calculated. Student's t-test was used to analyze the differences of the functional parameters between groups, and regression analysis and receiver operating characteristic (ROC) curves were used to explore the discrimination efficiency of DM patients from healthy subjects based on these functional parameters. Results: There was no significant difference in the baseline characteristics between the NDR and healthy normal groups. The ODRs of all vascular subgroups except the micro venule were significantly higher (p<0.05, respectively) while ODRv was significantly lower (p<0.001) in NDR group than that in healthy normal group. In the regression analysis, the increased ODRs except micro venule and decreased ODRv were significantly correlated with the incidence of DM, and the C-statistic for discrimination DM with all ODR is 0.777 (95% CI 0.687-0.867, p<0.001). Conclusion: A computational method to extract the retinal vascular oxygen-saturation-related optical density ratios (ODRs) with single color fundus photography was developed, and increased ODRs and decreased ODRv of retinal vessels could be new potential image biomarkers of DM.
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Affiliation(s)
| | | | | | | | | | | | | | - Jin Yuan
- *Correspondence: Jin Yuan, ; Peng Xiao,
| | - Peng Xiao
- *Correspondence: Jin Yuan, ; Peng Xiao,
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Akitegetse C, Landry P, Robidoux J, Lapointe N, Brouard D, Sauvageau D. Monte-Carlo simulation and tissue-phantom model for validation of ocular oximetry. BIOMEDICAL OPTICS EXPRESS 2022; 13:2929-2946. [PMID: 35774309 PMCID: PMC9203094 DOI: 10.1364/boe.458079] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 03/27/2022] [Accepted: 04/11/2022] [Indexed: 06/15/2023]
Abstract
Ocular oximetry, in which blood oxygen saturation is evaluated in retinal tissues, is a promising technique for the prevention, diagnosis and management of many diseases and conditions. However, the development of new tools for evaluating oxygen saturation in the eye fundus has often been limited by the lack of reference tools or techniques for such measurements. In this study, we describe a two-step validation method. The impact of scattering, blood volume fraction and lens yellowing on the oximetry model is investigated using a tissue phantom, while a Monte Carlo model of the light propagation in the eye fundus is used to study the effect of the fundus layered-structure. With this method, we were able to assess the performance of an ocular oximetry technique in the presence of confounding factors and to quantify the impact of the choroidal circulation on the accuracy of the measurements. The presented strategy will be useful to anyone involved in studies based on the eye fundus diffuse reflectance.
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Affiliation(s)
| | - Patricia Landry
- Affaires médicales et innovation, Héma-Québec, Québec, QC, G1V 5C3, Canada
| | - Jonathan Robidoux
- Affaires médicales et innovation, Héma-Québec, Québec, QC, G1V 5C3, Canada
| | | | - Danny Brouard
- Affaires médicales et innovation, Héma-Québec, Québec, QC, G1V 5C3, Canada
| | - Dominic Sauvageau
- Zilia inc., Québec, QC, G1K 3G5, Canada
- Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada
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7
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Karlsson RA, Hardarson SH. Artery vein classification in fundus images using serially connected U-Nets. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 216:106650. [PMID: 35139461 DOI: 10.1016/j.cmpb.2022.106650] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 01/12/2022] [Accepted: 01/18/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND AND OBJECTIVE Retinal vessels provide valuable information when diagnosing or monitoring various diseases affecting the retina and disorders affecting the cardiovascular or central nervous systems. Automated retinal vessel segmentation can assist clinicians and researchers when interpreting retinal images. As there are differences in both the structure and function of retinal arteries and veins, separating these two vessel types is essential. As manual segmentation of retinal images is impractical, an accurate automated method is required. METHODS In this paper, we propose a convolutional neural network based on serially connected U-nets that simultaneously segment the retinal vessels and classify them as arteries or veins. Detailed ablation experiments are performed to understand how the major components contribute to the overall system's performance. The proposed method is trained and tested on the public DRIVE and HRF datasets and a proprietary dataset. RESULTS The proposed convolutional neural network achieves an F1 score of 0.829 for vessel segmentation on the DRIVE dataset and an F1 score of 0.814 on the HRF dataset, consistent with the state-of-the-art methods on the former and outperforming the state-of-the-art on the latter. On the task of classifying the vessels into arteries and veins, the method achieves an F1 score of 0.952 for the DRIVE dataset exceeding the state-of-the-art performance. On the HRF dataset, the method achieves an F1 score of 0.966, which is consistent with the state-of-the-art. CONCLUSIONS The proposed method demonstrates competitive performance on both vessel segmentation and artery vein classification compared with state-of-the-art methods. The method outperforms human experts on the DRIVE dataset when classifying retinal images into arteries, veins, and background simultaneously. The method segments the vasculature on the proprietary dataset and classifies the retinal vessels accurately, even on challenging pathological images. The ablation experiments which utilize repeated runs for each configuration provide statistical evidence for the appropriateness of the proposed solution. Connecting several simple U-nets significantly improved artery vein classification performance. The proposed way of serially connecting base networks is not limited to the proposed base network or segmenting the retinal vessels and could be applied to other tasks.
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Affiliation(s)
- Robert Arnar Karlsson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, Reykjavík, 102, Iceland; Faculty of Electrical and Computer Engineering at the University of Iceland, Sæmundargata 2, Reykjavík, 102, Iceland.
| | - Sveinn Hakon Hardarson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, Reykjavík, 102, Iceland.
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8
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In-vivo functional and structural retinal imaging using multiwavelength photoacoustic remote sensing microscopy. Sci Rep 2022; 12:4562. [PMID: 35296738 PMCID: PMC8927130 DOI: 10.1038/s41598-022-08508-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 03/08/2022] [Indexed: 11/16/2022] Open
Abstract
Many important eye diseases as well as systemic disorders manifest themselves in the retina. Retinal imaging technologies are rapidly growing and can provide ever-increasing amounts of information about the structure, function, and molecular composition of retinal tissue in-vivo. Photoacoustic remote sensing (PARS) is a novel imaging modality based on all-optical detection of photoacoustic signals, which makes it suitable for a wide range of medical applications. In this study, PARS is applied for in-vivo imaging of the retina and estimating oxygen saturation in the retinal vasculature. To our knowledge, this is the first time that a non-contact photoacoustic imaging technique is applied for in-vivo imaging of the retina. Here, optical coherence tomography is also used as a well-established retinal imaging technique to navigate the PARS imaging beams and demonstrate the capabilities of the optical imaging setup. The system is applied for in-vivo imaging of both microanatomy and the microvasculature of the retina. The developed system has the potential to advance the understanding of the ocular environment and to help in monitoring of ophthalmic diseases.
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9
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Feng X, Yu Y, Zou D, Jin Z, Zhou C, Liu G, Fujimoto JG, Li C, Lu Y, Ren Q. Functional imaging of human retina using integrated multispectral and laser speckle contrast imaging. JOURNAL OF BIOPHOTONICS 2022; 15:e202100285. [PMID: 34726828 DOI: 10.1002/jbio.202100285] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/25/2021] [Accepted: 10/29/2021] [Indexed: 06/13/2023]
Abstract
A novel integration of retinal multispectral imaging (MSI), retinal oximetry and laser speckle contrast imaging (LSCI) is presented for functional imaging of retinal blood vessels that could potentially allow early detection or monitoring of functional changes. We designed and built a cost-effective, scalable, retinal imaging instrument that integrates structural and functional retinal imaging techniques, including MSI, retinal oximetry and LSCI. Color fundus imaging was performed with 470 nm, 550 nm and 600 nm wavelength light emitting diode (LED) illumination. Retinal oximetry was performed using 550 nm and 600 nm LED illumination. LSCI of blood flow was performed using 850 nm laser diode illumination at 82 frames per second. LSCI can visualize retinal and choroidal vasculature without requiring exogenous contrast agents and can provide time-resolved information on blood flow, generating a cardiac pulse waveform from retinal vasculature. The technology can rapidly acquire structural MSI images, retinal oximetry and LSCI blood flow information in a simplified clinical workflow without requiring patients to move between instruments. Results from multiple modalities can be combined and registered to provide structural as well as functional information on the retina. These advances can reduce barriers for clinical adoption, accelerating research using MSI, retinal oximetry and LSCI of blood flow for diagnosis, monitoring and elucidating disease pathogenesis.
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Affiliation(s)
- Ximeng Feng
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China
- Institute of Medical Technology, Peking University, Beijing, China
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
- National Biomedical Imaging Center, Beijing, China
| | - Yue Yu
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China
- Institute of Medical Technology, Peking University, Beijing, China
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
- National Biomedical Imaging Center, Beijing, China
| | - Da Zou
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China
- Institute of Medical Technology, Peking University, Beijing, China
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
- National Biomedical Imaging Center, Beijing, China
| | - Zi Jin
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Chuanqing Zhou
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Gangjun Liu
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
| | - James G Fujimoto
- Department of Electrical Engineering and Computer Science, Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Changhui Li
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China
- National Biomedical Imaging Center, Beijing, China
| | - Yanye Lu
- Institute of Medical Technology, Peking University, Beijing, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
| | - Qiushi Ren
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China
- Institute of Medical Technology, Peking University, Beijing, China
- Institute of Biomedical Engineering, Shenzhen Bay Laboratory, Shenzhen, China
- Institute of Biomedical Engineering, Peking University Shenzhen Graduate School, Shenzhen, China
- National Biomedical Imaging Center, Beijing, China
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10
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Karlsson RA, Olafsdottir OB, Helgadottir V, Belhadj S, Eliasdottir TS, Stefansson E, Hardarson SH. Automation improves repeatability of retinal oximetry measurements. PLoS One 2021; 16:e0260120. [PMID: 34914738 PMCID: PMC8675673 DOI: 10.1371/journal.pone.0260120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 11/02/2021] [Indexed: 11/19/2022] Open
Abstract
Purpose Retinal oximetry is a technique based on spectrophotometry where images are analyzed with software capable of calculating vessel oxygen saturation and vessel diameter. In this study, the effect of automation of measurements of retinal vessel oxygen saturation and vessel diameter is explored. Methods Until now, operators have had to choose each vessel segment to be measured explicitly. A new, automatic version of the software automatically selects the vessels once the operator defines a measurement area. Five operators analyzed image pairs from the right eye of 23 healthy subjects with semiautomated retinal oximetry analysis software, Oxymap Analyzer (v2.5.1), and an automated version (v3.0). Inter- and intra-operator variability was investigated using the intraclass correlation coefficient (ICC) between oxygen saturation measurements of vessel segments in the same area of the retina. Results For semiautomated saturation measurements, the inter-rater ICC was 0.80 for arterioles and venules. For automated saturation measurements, the inter-rater ICC was 0.97 for arterioles and 0.96 for venules. For semiautomated diameter measurements, the inter-rater ICC was 0.71 for arterioles and venules. For automated diameter measurements the inter-rater ICC was 0.97 for arterioles and 0.95 for venules. The inter-rater ICCs were different (p < 0.01) between the semiautomated and automated version in all instances. Conclusion Automated measurements of retinal oximetry values are more repeatable compared to measurements where vessels are selected manually.
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Affiliation(s)
- Robert Arnar Karlsson
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Faculty of Electrical and Computer Engineering, University of Iceland, Reykjavik, Iceland
- * E-mail:
| | - Olof Birna Olafsdottir
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- The National University Hospital of Iceland, Reykjavik, Iceland
| | | | | | - Thorunn Scheving Eliasdottir
- The National University Hospital of Iceland, Reykjavik, Iceland
- Faculty of Nursing, University of Iceland, Reykjavik, Iceland
| | - Einar Stefansson
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- The National University Hospital of Iceland, Reykjavik, Iceland
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Vehmeijer WB, Jonkman K, Hardarson SH, Aarts L, Stefansson E, Dahan A, Schalij‐Delfos NE. Retinal oximetry with a prototype handheld oximeter during hyperoxia. Acta Ophthalmol 2021; 99:e1390-e1395. [PMID: 33650317 PMCID: PMC9543559 DOI: 10.1111/aos.14817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 01/29/2021] [Accepted: 02/04/2021] [Indexed: 11/30/2022]
Abstract
PURPOSE Retinal oximetry measures oxygen saturation in retinal vessels. With the introduction of a mobile handheld prototype oximeter, this technique will become available for a broader patient population including bedridden patients and newborn babies. The objective is to determine the sensitivity of this handheld oximeter in room air and during isocapnic hyperoxia. A comparison is made between the handheld oximeter and the Oxymap T1. METHODS Thirteen young healthy subjects with a mean age of 25 ± 2 years were recruited at the Leiden University Medical Center. Retinal oximetry images were acquired during normoxia and during isocapnic hyperoxia for both the prototype oximeter and the OxymapT1. Isocapnic hyperoxia was induced with the dynamic end-tidal forcing technique. For both oximeters, the oxygen saturation and vessel width were measured with Oxymap Analyzer software. The hyperoxic state was verified with blood gas analysis. RESULTS The mean oxygen saturation measured with the handheld oximeter in arterioles was 91.3% ± 3.9% during normoxia and 94.6% ± 3.9% during hyperoxia (p = 0.001). Oxygen saturation in venules was 56.3% ± 9.8% during normoxia and 82.2 ± 7.4% during hyperoxia (p < 0.001). For the Oxymap T1, the mean oxygen saturation for arterioles was 94.0% ± 2.6% during normoxia and 95.4%±3.2% during hyperoxia (p = 0.004). For the venules, the oxygen saturation was during normoxia 58.9%±3.2% and 84.3 ± 4.0% during hyperoxia (p < 0.001). CONCLUSION The handheld retinal oximeter is sensitive to the changes in inhaled oxygen concentration. A small increase in oxygen saturation was measured in the arterioles and a larger increase in the venules. The handheld oximeter gives similar values as the 'gold standard' Oxymap T1 oximeter.
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Affiliation(s)
- Wouter B. Vehmeijer
- Department of Ophthalmology Leiden University Medical Center Leiden The Netherlands
| | - Kelly Jonkman
- Department of Anesthesiology Leiden University Medical Center Leiden The Netherlands
| | | | - Leon Aarts
- Department of Anesthesiology Leiden University Medical Center Leiden The Netherlands
| | - Einar Stefansson
- Department of Physiology University of Iceland Reykjavik Iceland
- Department of Ophthalmology University of Iceland Landspítali, Reykjavik Iceland
| | - Albert Dahan
- Department of Anesthesiology Leiden University Medical Center Leiden The Netherlands
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12
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Belamkar AV, Jabbehdari S, Harris A, Hajrasouliha AR. Clinical implications of retinal oximetry in retinal vein occlusion: a review. Acta Ophthalmol 2021; 100:624-631. [PMID: 34845846 DOI: 10.1111/aos.15066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/28/2021] [Accepted: 11/19/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE To review retinal vein occlusion (RVO) and its relationship with retinal oxygen saturation via automated retinal oximetry in eyes with RVO. METHODS A literature review was performed in PubMed and Medline until October 2021 utilizing specific keywords and cross-matched reference lists. RESULTS This review found RVO to be associated with risk factors including age, hypertension, cardiovascular and metabolic conditions, male gender, and glaucoma. These may be attributed to a breakdown of regulatory processes in the retina. Retinal venous oxygen saturation (SvO2 ) and arteriovenous difference in eyes with central RVO have been found to be reduced and elevated, respectively. The literature indicates variable and contradictory findings in regard to branch RVO and retinal oxygenation. Additionally, ischaemic eyes have been found to have elevated retinal arterial oxygen saturation; however, the literature reports variable results regarding SvO2 levels. Medications have been suggested to increase SvO2 in RVO eyes, which may represent an important mechanism for disease management. Ranibizumab is currently the most studied drug for retinal oxygenation in RVO and has been suggested to increase SvO2 in RVO eyes. In comparison, dexamethasone was found to decrease SvO2 . CONCLUSION The current literature on retinal oxygenation in ischaemic subtypes of RVO and in drug therapies is minimal, and further work is required to expand upon our understanding of how ischaemia and drugs influence retinal oxygenation and clinical outcomes.
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Affiliation(s)
- Aditya V. Belamkar
- Glick Eye Institute Department of Ophthalmology Indiana University School of Medicine Indianapolis Indiana USA
| | - Sayena Jabbehdari
- Jones Eye Institute University of Arkansas for Medical Sciences Little Rock Arkansas USA
| | - Alon Harris
- Icahn School of Medicine at Mount Sinai Ophthalmic Vascular Diagnostic and Research Program at Mount Sinai Hospital New York New York USA
| | - Amir R. Hajrasouliha
- Glick Eye Institute Department of Ophthalmology Indiana University School of Medicine Indianapolis Indiana USA
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13
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Abstract
Advances in retinal imaging are enabling researchers and clinicians to make precise noninvasive measurements of the retinal vasculature in vivo. This includes measurements of capillary blood flow, the regulation of blood flow, and the delivery of oxygen, as well as mapping of perfused blood vessels. These advances promise to revolutionize our understanding of vascular regulation, as well as the management of retinal vascular diseases. This review provides an overview of imaging and optical measurements of the function and structure of the ocular vasculature. We include general characteristics of vascular systems with an emphasis on the eye and its unique status. The functions of vascular systems are discussed, along with physical principles governing flow and its regulation. Vascular measurement techniques based on reflectance and absorption are briefly introduced, emphasizing ways of generating contrast. One of the prime ways to enhance contrast within vessels is to use techniques sensitive to the motion of cells, allowing precise measurements of perfusion and blood velocity. Finally, we provide a brief introduction to retinal vascular diseases.
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Affiliation(s)
- Stephen A Burns
- Indiana University School of Optometry, Bloomington, Indiana 47405, USA; , ,
| | - Ann E Elsner
- Indiana University School of Optometry, Bloomington, Indiana 47405, USA; , ,
| | - Thomas J Gast
- Indiana University School of Optometry, Bloomington, Indiana 47405, USA; , ,
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14
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Abstract
Similar to other organs, the retina relies on tightly regulated perfusion and oxygenation. Previous studies have demonstrated that retinal blood flow is affected in a variety of eye and systemic diseases, including diabetic retinopathy, age-related macular degeneration, and glaucoma. Although measurement of peripheral oxygen saturation has become a standard clinical measurement through the development of pulse oximetry, developing a noninvasive technique to measure retinal oxygen saturation has proven challenging, and retinal oximetry technology currently remains inadequate for reliable clinical use. Here, we review current strategies and approaches, as well as several newer technologies in development, and discuss the future of retinal oximetry.
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Affiliation(s)
- Anupam K Garg
- Shiley Eye Institute, Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA.,School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Darren Knight
- Shiley Eye Institute, Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Leonardo Lando
- Shiley Eye Institute, Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA
| | - Daniel L Chao
- Shiley Eye Institute, Viterbi Family Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA.,School of Medicine, University of California San Diego, La Jolla, CA, USA.,Janssen Research and Development, Raritan, NJ, USA
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15
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Hardarson SH, Stefánsson E, Bek T. Retinal oxygen saturation changes progressively over time in diabetic retinopathy. PLoS One 2021; 16:e0251607. [PMID: 33979414 PMCID: PMC8115819 DOI: 10.1371/journal.pone.0251607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/28/2021] [Indexed: 11/19/2022] Open
Abstract
PURPOSE According to cross-sectional studies, oxygen saturation is elevated in retinal vessels in diabetic patients. We evaluated how retinal oxygenation (metabolic marker), vessel diameters and retinopathy grade (structural markers) change over time in diabetic patients. DESIGN Prospective cohort study following screening in a hospital setting. METHODS Retinal oximetry images were acquired in 214 patients with the Oxymap T1 oximeter. Imaging was repeated after a median of 3.0 years (range 0.76-6.8 years). Oxygen saturation and vessel diameters were measured in the right eye. Semiquantitative grading of retinopathy according to international guidelines and red lesion count were performed on fundus photographs. RESULTS Retinopathy grade according to the international semiquantitative grading system was unchanged. Arteriolar saturation increased by 0.75±0.15 percentage points per year of follow-up (p<0.0001). Venular saturation increased by 1.74±0.26 percentage points per year (p<0.0001) and arteriovenous difference decreased by 0.99±0.20 percentage points per year (p<0.0001). Arteriolar diameters decreased by 2.7±8.5μm (p<0.0001) between visits and venular diameters decreased by 2.4±9.1μm (p = 0.0002). Median increase in red lesion count between visits was 2 lesions (range -128 to 212 lesions, p<0.0001). The change in red lesion count and change in diameters did not correlate with the length of follow-up (p>0.44). CONCLUSIONS Oxygen saturation in larger retinal vessels can increase and arteriovenous difference can decrease over time in diabetic patients without any observable changes in retinopathy grade. The results suggest that changes in retinal oxygen saturation may precede progression of diabetic retinopathy or that oxygen saturation is more sensitive to disease progression than retinopathy grade.
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Affiliation(s)
- Sveinn Hakon Hardarson
- Institute of Physiology, Department of Medicine, University of Iceland, Reykjavik, Iceland
- * E-mail:
| | - Einar Stefánsson
- Institute of Physiology, Department of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Ophthalmology, Landspitali University Hospital, Reykjavik, Iceland
| | - Toke Bek
- Department of Ophthalmology, Aarhus University Hospital, Aarhus N, Denmark
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16
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Karlsson RA, Jonsson BA, Hardarson SH, Olafsdottir OB, Halldorsson GH, Stefansson E. Automatic fundus image quality assessment on a continuous scale. Comput Biol Med 2020; 129:104114. [PMID: 33260100 DOI: 10.1016/j.compbiomed.2020.104114] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 11/03/2020] [Accepted: 11/07/2020] [Indexed: 12/22/2022]
Abstract
Fundus photography is commonly used for screening, diagnosis, and monitoring of various diseases affecting the eye. In addition, it has shown promise in the diagnosis of brain diseases and evaluation of cardiovascular risk factors. Good image quality is important if diagnosis is to be accurate and timely. Here, we propose a method that automatically grades image quality on a continuous scale which is more flexible than binary quality classification. The method utilizes random forest regression models trained on image features discovered automatically by combining basic image filters using simulated annealing as well as features extracted with the discrete Fourier transform. The method was developed and tested on images from two different fundus camera models. The quality of those images was rated on a continuous scale from 0.0 to 1.0 by five experts. In addition, the method was tested on DRIMDB, a publicly available dataset with binary quality ratings. On the DRIMDB dataset the method achieves an accuracy of 0.981, sensitivity of 0.993 and specificity of 0.958 which is consistent with the state of the art. When evaluating image quality on a continuous scale the method outperforms human raters.
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Affiliation(s)
- Robert A Karlsson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, 102, Reykjavík, Iceland; Faculty of Electrical and Computer Engineering at the University of Iceland, Sæmundargata 2, 102, Reykjavík, Iceland.
| | - Benedikt A Jonsson
- Faculty of Electrical and Computer Engineering at the University of Iceland, Sæmundargata 2, 102, Reykjavík, Iceland
| | - Sveinn H Hardarson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, 102, Reykjavík, Iceland
| | - Olof B Olafsdottir
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, 102, Reykjavík, Iceland; Landspitali - the National University Hospital of Iceland, Hringbraut 10, 101, Reykjavík, Iceland
| | | | - Einar Stefansson
- Faculty of Medicine at the University of Iceland, Sæmundargata 2, 102, Reykjavík, Iceland; Landspitali - the National University Hospital of Iceland, Hringbraut 10, 101, Reykjavík, Iceland
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Shughoury A, Mathew S, Arciero J, Wurster P, Adjei S, Ciulla T, Siesky B, Harris A. Retinal oximetry in glaucoma: investigations and findings reviewed. Acta Ophthalmol 2020; 98:559-571. [PMID: 32248646 DOI: 10.1111/aos.14397] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 02/20/2020] [Indexed: 12/17/2022]
Abstract
Abnormalities of the retinal blood supply have been widely implicated in primary open-angle glaucoma (POAG). Impaired blood supply to the retina and optic nerve head (ONH) may be a primary pathophysiologic mechanism contributing to POAG ('vascular hypothesis'). However, the decreased metabolic activity of atrophic tissue is itself known to induce both vascular changes and decreased blood flow due to reduced oxygen demand. Therefore, primary nonvascular factors could potentially induce glaucomatous atrophy, with subsequent secondary vascular pathology ('mechanical hypothesis'). Retinal oximetry holds great promise in the investigation of glaucoma pathogenesis, as it can provide useful data on retinal metabolic oxygen demand, especially when combined with measurements of retinal blood flow. This review surveys the research on retinal metabolism in POAG using spectroscopic retinal oximetry. The use of mathematical models in combination with oximetric data to investigate the role of retinal metabolism and oxygen supply in POAG is also discussed.
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Affiliation(s)
- Aumer Shughoury
- Eugene and Marilyn Glick Eye Institute Department of Ophthalmology Indiana University School of Medicine Indianapolis IN USA
| | - Sunu Mathew
- Eugene and Marilyn Glick Eye Institute Department of Ophthalmology Indiana University School of Medicine Indianapolis IN USA
| | - Julia Arciero
- Department of Mathematical Sciences Indiana University Purdue University Indianapolis IN USA
| | - Patrick Wurster
- Eugene and Marilyn Glick Eye Institute Department of Ophthalmology Indiana University School of Medicine Indianapolis IN USA
| | - Susuana Adjei
- Eugene and Marilyn Glick Eye Institute Department of Ophthalmology Indiana University School of Medicine Indianapolis IN USA
| | | | - Brent Siesky
- Icahn School of Medicine at Mount Sinai New York NY USA
| | - Alon Harris
- Icahn School of Medicine at Mount Sinai New York NY USA
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18
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Heitmar R, Cubbidge RP. Retinal Vessel Oxygen Saturation Measurement Protocols and Their Agreement. Transl Vis Sci Technol 2020; 9:17. [PMID: 32821514 PMCID: PMC7409221 DOI: 10.1167/tvst.9.6.17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/04/2020] [Indexed: 12/01/2022] Open
Abstract
Purpose To assess agreement between different image sizes and analysis protocols for determination of retinal vessel oxygen saturation in the peripapillary retina of healthy individuals. Methods Retinal oximetry measurements were acquired from 87 healthy volunteers using the IMEDOS Systems oxygen module. The peripapillary retinal vessels were assessed in a concentric annulus around the optic nerve head. Single and average vessel comparisons were made at different image field sizes of 30° and 50°. Comparisons between images obtained at 30° and 50° were made in a subset of 47 of the 87 individuals. Results All subjects were normotensive and had normal intraocular pressures (9–16 mm Hg). Analyses of agreement between single vessel, averaged vessel, and between different size images were sought by Bland-Altman analyses, of which all yielded a low bias (<1% oxygen saturation). However, agreement between single vessels of consecutive images showed increased limits of agreement compared with saturation values calculated by averaging all or just the four major arcades of one image. Agreement between 30° and 50° images showed a similar bias as when comparing data obtained with the same camera angle setting but exhibited larger confidence intervals (arteries: bias = 0.21% [9.04/–8.62]%; veins: bias = 0.71% [14.82/–13.40]%). Conclusions Averaging methods yielded the best agreement; there was little difference in average arterial and venous oxygen saturation between protocols, which analyze all vessels versus the four largest vessels. The least agreement was found for single vessel measurements and comparisons between different camera angles. Translational Relevance Standardization of image capture protocols (same image size and undertaking a vessel averaging approach for oxygenation analysis) will enhance the detection of smaller physiological changes in eye disease.
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Affiliation(s)
- Rebekka Heitmar
- School of Life and Health Sciences, Aston University, Birmingham, UK
| | - Robert P Cubbidge
- School of Life and Health Sciences, Aston University, Birmingham, UK
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19
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Retinal oximetry and fractal analysis of capillary maps in sickle cell disease patients and matched healthy volunteers. Graefes Arch Clin Exp Ophthalmol 2019; 258:9-15. [PMID: 31529320 DOI: 10.1007/s00417-019-04458-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 08/19/2019] [Accepted: 08/29/2019] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Fractal analysis can be used to quantitatively analyze the retinal microvasculature and might be a suitable method to quantify retinal capillary changes in sickle cell disease (SCD) patients. Retinal oximetry measurements might function as a proxy for the pathophysiology of cerebrovascular diseases. Moreover, hypoxia has an important role in the pathophysiology of diabetic and other retinopathies. However, little is known about the oximetry around the macula in SCD patients. With this study, we explored the feasibility to perform these quantified measurements in SCD patients. METHODS Retinal microvascular and oximetry measurements were performed in eight SCD patients and eight healthy matched controls. Oximetry pictures and non-invasive capillary perfusion maps (nCPM) were obtained by the retinal function imager. Measurements were conducted twice on two different study days. Measured variables included monofractal dimension (Dbox), relative saturation, deoxygenated hemoglobin (deoxyHb), and oxygenated hemoglobin (oxyHb) concentration. RESULTS No statistically significant differences in vessel density were found in the different annular zones (large vessels, p = 0.66; small vessels, p = 0.66) and anatomical quadrants (large vessels, p = 0.74; small vessels, p = 0.72). Furthermore, no significant between-group differences were found in the other different anatomical quadrants and annular zones around the fovea for relative saturation levels and deoxygenated Hb. However, the oxyHb levels were significantly lower in SCD patients, compared with those in matched controls in the temporal quadrants (p = 0.04; p = 0.02) and the superior nasal quadrant (p = 0.05). CONCLUSIONS Our study demonstrated the feasibility of multispectral imaging to measure retinal changes in oxygenation in both SCD patients and matched volunteers. The results suggest that in SCD patients before any structural microvascular changes in the central retina are present, functional abnormalities can be observed with abnormal oximetry measurements.
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20
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Convolutional Neural Networks for Spectroscopic Analysis in Retinal Oximetry. Sci Rep 2019; 9:11387. [PMID: 31388136 PMCID: PMC6684811 DOI: 10.1038/s41598-019-47621-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 06/20/2019] [Indexed: 01/06/2023] Open
Abstract
Retinal oximetry is a non-invasive technique to investigate the hemodynamics, vasculature and health of the eye. Current techniques for retinal oximetry have been plagued by quantitatively inconsistent measurements and this has greatly limited their adoption in clinical environments. To become clinically relevant oximetry measurements must become reliable and reproducible across studies and locations. To this end, we have developed a convolutional neural network algorithm for multi-wavelength oximetry, showing a greatly improved calculation performance in comparison to previously reported techniques. The algorithm is calibration free, performs sensing of the four main hemoglobin conformations with no prior knowledge of their characteristic absorption spectra and, due to the convolution-based calculation, is invariable to spectral shifting. We show, herein, the dramatic performance improvements in using this algorithm to deduce effective oxygenation (SO2), as well as the added functionality to accurately measure fractional oxygenation (\documentclass[12pt]{minimal}
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\begin{document}$${{\bf{SO}}}_{{\bf{2}}}^{{\boldsymbol{f}}{\boldsymbol{r}}}$$\end{document}SO2fr). Furthermore, this report compares, for the first time, the relative performance of several previously reported multi-wavelength oximetry algorithms in the face of controlled spectral variations. The improved ability of the algorithm to accurately and independently measure hemoglobin concentrations offers a high potential tool for disease diagnosis and monitoring when applied to retinal spectroscopy.
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Dwight JG, Weng CY, Pawlowski ME, Tkaczyk TS. A Dye-Free Analog to Retinal Angiography Using Hyperspectral Unmixing to Retrieve Oxyhemoglobin Abundance. Transl Vis Sci Technol 2019; 8:44. [PMID: 31259089 PMCID: PMC6590091 DOI: 10.1167/tvst.8.3.44] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 04/15/2019] [Indexed: 01/24/2023] Open
Abstract
Purpose Retinal angiography evaluates retinal and choroidal perfusion and vascular integrity and is used to manage many ophthalmic diseases, such as age-related macular degeneration. The most common method, fluorescein angiography (FA), is invasive and can lead to untoward effects. As an emerging replacement, noninvasive OCT angiography (OCTA) is used regularly as a dye-free substitute with superior resolution and additional depth-sectioning abilities; however, general trends in FA as signified by varying intensity in images are not always reproducible in the fine structural detail in an OCTA image stack because of the source of their respective signals, OCT speckle decorrelation versus fluorescein emission. Methods We present a noninvasive/dye-free analog to angiography imaging using retinal hyperspectral imaging with a nonscanning spectral imager, the image mapping spectrometer (IMS), to reproduce perfusion-related data based on the abundance of oxyhemoglobin (HbO2) in the retina. With a new unmixing procedure of the IMS-acquired spectral data cubes (350 × 350 × 43), we produced noninvasive HbO2 maps unmixed from reflectance spectra. Results Here, we present 15 HbO2 maps from seven healthy and eight diseased retinas and compare these maps with corresponding FA and OCTA results with a discussion of each technique. Conclusions Our maps showed visual agreement with hypo- and hyperfluorescence trends in venous phase FA images, suggesting that our method provides a new use for hyperspectral imaging as a noninvasive angiography-analog technique and as a complementary technique to OCTA. Translational Relevance The application of hyperspectral imaging and spectral analysis can potentially improve/broaden retinal disease screening and enable a noninvasive technique, which complements OCTA.
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Affiliation(s)
- Jason G Dwight
- Department of Bioengineering, Rice University, Houston, TX, USA
| | - Christina Y Weng
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
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22
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Chen H, Liu G, Zhang S, Shen S, Luo Y, Li J, Roberts CJ, Sun M, Xu RX. Fundus-simulating phantom for calibration of retinal vessel oximetry devices. APPLIED OPTICS 2019; 58:3877-3885. [PMID: 31158206 DOI: 10.1364/ao.58.003877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 04/10/2019] [Indexed: 06/09/2023]
Abstract
Retinal vessel oxygen supply is important for retinal tissue metabolism. Commonly used retinal vessel oximetry devices are based on dual-wavelength spectral measurement of oxyhemoglobin and deoxyhemoglobin. However, there is no traceable standard for reliable calibration of these devices. In this study, we developed a fundus-simulating phantom that closely mimicked the optical properties of human fundus tissues. Microchannels of precisely controlled topological structures were produced by soft lithography to simulate the retinal vasculature. Optical properties of the phantom were adjusted by adding scattering and absorption agents to simulate different concentrations of fundus pigments. The developed phantom was used to calibrate the linear correlation between oxygen saturation (SO2) level and optical density ratio in a dual-wavelength oximetry device. The obtained calibration factors were used to calculate the retinal vessel SO2 in both eyes of five volunteers aged between 24 and 27 years old. The test results showed that the mean arterial and venous SO2 levels after phantom calibration were coincident with those after empirical value calibration, indicating the potential clinical utility of the produced phantom as a calibration standard.
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23
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Van Keer K, Van Keer J, Barbosa Breda J, Nassiri V, Van Cleemput J, Abegão Pinto L, Stalmans I, Vandewalle E. Retinal oxygen saturation as a non-invasive estimate for mixed venous oxygen saturation and cardiac output. Acta Ophthalmol 2019; 97:e308-e312. [PMID: 30280510 DOI: 10.1111/aos.13890] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 07/18/2018] [Indexed: 01/15/2023]
Abstract
PURPOSE To investigate the correlation between retinal vessel oxygen saturation and mixed venous oxygen saturation (SvO2-mixed ) and cardiac output (CO). METHODS Retinal arterial (SaO2-retinal ) and venous (SvO2-retinal ) oxygen saturation were measured non-invasively with dual-wavelength retinal oximetry in subjects receiving invasive measurements of SvO2-mixed and CO through right heart catheterization. Correlations were analysed using Spearman's rank correlation coefficients and linear regression models. RESULTS Fourteen patients (median age 62.7 years, range: 21-77) were included in the analysis. When adjusted for age, SvO2-retinal showed a positive correlation with SvO2-mixed (β = 0.80, p = 0.003). Retinal arteriovenous oxygen saturation difference was significantly correlated with the inverse of CO (Spearman's ρ = 0.59, p = 0.026). CONCLUSION This pilot study provides proof of concept for the use of retinal oximetry as a non-invasive tool to assess systemic cardiovascular function.
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Affiliation(s)
- Karel Van Keer
- Department of Ophthalmology University Hospitals Leuven Leuven Belgium
- Research Group Ophthalmology Department of Neurosciences KU Leuven Leuven Belgium
| | - Jan Van Keer
- Department of Cardiology University Hospitals Leuven Leuven Belgium
| | - João Barbosa Breda
- Department of Ophthalmology University Hospitals Leuven Leuven Belgium
- Research Group Ophthalmology Department of Neurosciences KU Leuven Leuven Belgium
- Department of Ophthalmology Centro Hospitalar São João Porto Portugal
| | | | | | - Luìs Abegão Pinto
- Department of Ophthalmology Lisbon North Hospital Centre Lisbon Portugal
| | - Ingeborg Stalmans
- Department of Ophthalmology University Hospitals Leuven Leuven Belgium
- Research Group Ophthalmology Department of Neurosciences KU Leuven Leuven Belgium
| | - Evelien Vandewalle
- Department of Ophthalmology University Hospitals Leuven Leuven Belgium
- Research Group Ophthalmology Department of Neurosciences KU Leuven Leuven Belgium
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Abstract
PURPOSE Continuous peripheral pulse oximetry for monitoring adequacy of oxygenation is probably the most important technological advance for patients' monitoring and safety in the last decades. Pulse oximetry has the disadvantage of measuring the peripheral circulation, and the only mean to measure oxygen content of the central circulation is by invasive technology. Determination of blood oxyhaemoglobin saturation in the retinal vessels of the eye can be achieved noninvasively through spectrophotometric retinal oximetry which provides access to the central nervous system circulation. The aim of the thesis was to determine whether retinal oximetry technique can be applied for estimation of the central nervous system circulation which until now has only been possible invasively. This was achieved by measuring oxyhaemoglobin saturation in three adult subject study groups: in people with central retinal vein occlusion (CRVO) to observe local tissue hypoxia, in patients with severe chronic obstructive pulmonary disease (COPD) on long-term oxygen therapy to observe systemic hypoxaemia and in healthy subjects during hyperoxic breathing to observe systemic hyperoxemia. In addition, the fourth study that is mentioned was performed to test whether retinal oximetry is feasible for neonates. METHODS Retinal oximetry in central retinal vein occlusion: Sixteen subjects with central retinal vein occlusion participated in the study. The oxyhaemoglobin saturation of the central retinal vein occlusion affected eye was compared with the fellow unaffected eye. Retinal oximetry in healthy people under hyperoxia: Thirty healthy subjects participated in the study, and the oxyhaemoglobin saturation of retinal arterioles and venules was compared between normoxic and hyperoxic breathing. Retinal oximetry in severe chronic obstructive pulmonary disease: Eleven patients with severe chronic obstructive pulmonary disease participated in the study. Retinal oximetry measurements were made with and without their daily supplemental oxygen therapy. Retinal arteriolar oxyhaemoglobin saturation when inspiring ambient air was compared with blood samples from the radial artery and finger pulse oximetry and healthy controls. The healthy control group was assembled from our database for comparison of oxyhaemoglobin saturation of retinal arterioles and venules during the ambient air breathing. The retinal oximeter is based on a conventional fundus camera and a specialized software. A beam splitter coupled with two high-resolution digital cameras allows for simultaneous acquisition of retinal images at separative wavelengths for calculation of oxyhaemoglobin saturation. In addition, retinal images of 28 full-term healthy neonates were obtained with scanning laser ophthalmoscope combined with modified Oxymap analysis software for calculation of the optical density ratio and vessel diameter RESULTS: Retinal oximetry in central retinal vein occlusion: Mean retinal venous oxyhaemoglobin saturation was 31 ± 12% in CRVO eyes and 52 ± 11% in unaffected fellow eyes (mean ± SD, n = 14, p < 0.0001). The arteriovenous oxygen difference (AV-difference) was 63 ± 11% in CRVO eyes and 43 ± 7% in fellow eyes (p < 0.0001). The variability of retinal venous oxyhaemoglobin saturation was considerable within and between eyes affected by CRVO. There was no difference in oxyhaemoglobin saturation of retinal arterioles between the CRVO eyes and the unaffected eyes (p = 0.49). Retinal oximetry in healthy people under hyperoxia: During hyperoxic breathing, the oxyhaemoglobin saturation in retinal arterioles increased to 94.5 ± 3.8% as compared with 92.0 ± 3.7% at baseline (n = 30, p < 0.0001). In venules, the mean oxyhaemoglobin saturation increased to 76.2 ± 8.0% from 51.3 ± 5.6% (p < 0.0001) at baseline. The AV-difference was markedly lower during hyperoxic breathing as compared with the normoxic breathing (18.3 ± 9.0% versus 40.7 ± 5.7%, p < 0.0001). Retinal oximetry in severe chronic obstructive pulmonary disease: During ambient air breathing, chronic obstructive pulmonary disease subjects had significantly lower oxyhaemoglobin saturation than healthy controls in both retinal arterioles (87.2 ± 4.9% versus 93.4 ± 4.3%, p = 0.02, n = 11) and venules (45.0 ± 10.3% versus 55.2 ± 5.5%, p = 0.01) but the AV-difference was not markedly different (p = 0.17). Administration of their prescribed oxygen therapy significantly increased the oxyhaemoglobin saturation in retinal arterioles (87.2 ± 4.9% to 89.5 ± 6.0%, p = 0.02) but not in venules (45.0 ± 10.3% to 46.7 ± 12.8%, p = 0.3). Retinal oximetry values were slightly lower than finger pulse oximetry (mean percentage points difference = -3.1 ± 5.5) and radial artery blood values (-5.0 ± 5.4). Retinal oximetry study in neonates: The modified version of the retinal oximetry instrument estimated the optical density ratio in retinal arterioles to be 0.256 ± 0.041 that was significantly different from the 0.421 ± 0.089 in venules (n = 28, p < 0.001, paired t-test). The vascular diameter of retinal arterioles was markedly narrower than of venules (14.1 ± 2.7 and 19.7 ± 3.7 pixels, p < 0.001). CONCLUSION The results of this thesis indicate that spectrophotometric retinal oximetry is sensitive to both local and systemic changes in oxyhaemoglobin saturation. Retinal oxyhaemoglobin saturation values are slightly lower than radial artery blood sample and finger pulse oximetry values. The discrepancies between the different modalities are expected to derive from countercurrent exchange between central retinal artery and vein within the optic nerve but calibration issues cannot be excluded as contributing to this difference. Despite these differences, the findings indicate the potential of retinal oximetry for noninvasive real-time measurements of oxyhaemoglobin saturation in central nervous system vessels. Following calibration upgrade and technological improvement, verification retinal oximetry may potentially be applied to critically ill and anaesthesia care patients. The study on combined scanning laser ophthalmoscope and retinal oximetry supports the feasibility of the technique for oximetry analysis in newly born babies.
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Vehmeijer W, Hardarson SH, Jonkman K, Aarts L, Dahan A, Stefánsson E, Schalij-Delfos N. Handheld Retinal Oximetry in Healthy Young Adults. Transl Vis Sci Technol 2018; 7:19. [PMID: 30174997 PMCID: PMC6114026 DOI: 10.1167/tvst.7.4.19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 06/19/2018] [Indexed: 11/24/2022] Open
Abstract
Purpose The objective of this study was to measure the relative retinal oxygen saturation with a prototype, mobile handheld oximeter in upright and supine position and to compare these measurements to the gold standard Oxymap T1 retinal oximeter in upright position. A handheld oximeter is needed for measurements of infants with retinopathy of prematurity as well as acutely injured and bedridden adults. Methods Healthy volunteers (age 18–35) were recruited at the Leiden University Medical Center. Retinal images were acquired with the handheld oximeter and the Oxymap T1. Both cameras are dual-wavelength oximeters and acquire images with wavelengths of 570 and 600 nm. Retinal oxygen saturation values were determined for both the handheld camera and the Oxymap T1. Results Twenty-one subjects (age 25 ± 2 years) were included. In upright position, the oxygen saturation for the arterioles was 92.2% to 4.9% vs. 95.5% ± 4.2% and for the venules 57.9% ± 10.2% vs. 57.7% ± 6.4% for the handheld camera and Oxymap T1, respectively. The oxygen saturation was higher in the arterioles than the venules for both cameras (P < 0.05). In supine position, measured with the handheld oximeter, the oxygen saturation in the arterioles was 92.3% ± 5.8% and 59.2% ± 6.1% in the venules. Conclusions Performance of the prototype, mobile handheld oximeter Corimap camera compares well with the Oxymap T1, with a slightly larger standard deviation in oxygen saturation measurements, both in upright and supine patients. Translation Relevance To date, to our knowledge, no oximeters are available for handheld use and for measurement in supine position in infants and bedridden adults. Here we tested such an oximeter and show that its performance compares well with that of the gold standard Oxymap T1 in healthy adults.
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Affiliation(s)
- Wouter Vehmeijer
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Kelly Jonkman
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Leon Aarts
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
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Farage MA, Cambron T, Liu KZ. Visible-Near Infrared Spectroscopic Assessment of Urogenital Tissue in Premenopausal and Postmenopausal Women. CLINICAL MEDICINE INSIGHTS. WOMEN'S HEALTH 2018; 11:1179562X17749608. [PMID: 29344000 PMCID: PMC5761901 DOI: 10.1177/1179562x17749608] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 11/20/2017] [Indexed: 12/25/2022]
Abstract
BACKGROUND A clinical study was conducted to evaluate the feasibility of using visible and near-infrared (NIR) spectroscopy as a potential noninvasive measure of genital skin health in premenopausal and postmenopausal women. METHODS A total of 45 female subjects (aged 21-70 years), all of whom gave fully informed consent to participate, were enrolled in the study and assigned to 1 of 3 groups: 15 premenopausal (Pre-M), 15 postmenopausal receiving hormone replacement therapy (Post-M HRT), and 15 postmenopausal receiving no form of hormone replacement therapy (Post-M non-HRT). Spectral measurements were taken at the vaginal mucosa, and spectral data were evaluated for the erythema index (EI), hemoglobin index (HI), bilirubin/β-carotene, and melanin. The color index (CI; calculated as the ratio of absorbance at 480 nm/540 nm) was also determined. Results were compared with previously published results on biomarkers and physical characteristic of genital tissue measured on the same groups of women. RESULTS Spectral measurements from the Post-M Non-HRT subjects indicated a significant reduction in HI compared with the Pre-M group (P = .0003) and to the Post-M HRT group (P < .0001). Similarly, EI was reduced in the Post-M Non-HRT (P < .0001 and P = .0041 for the Pre-M and Post-M HRT groups, respectively). In contrast, the Post-M Non-HRT subjects exhibited a significant increase in β-carotene compared with the Pre-M subjects (P = .0098). Bilirubin and melanin were not significantly affected. The Post-M Non-HRT group exhibited a significant increase in CI, indicating a shift away from the hemoglobin absorption region (510-620 nm wavelength) and toward the bilirubin/β-carotene absorption region (450-490 nm wavelength). This change was significant when compared with both the Pre-M group (P < .0001) and the Post-M HRT group (P = .0048). The changes in spectral measurements were consistent with previously reported changes in physical parameters (vaginal atrophy, increased pH, decreased skin temperature) and with decreased concentrations of the biomarkers histamine and histidine. CONCLUSIONS Hemodynamic spectral characteristics differ in postmenopausal vaginal tissue compared with tissue in premenopausal women, with decreased absorbance in the hemoglobin absorption region (510-620 nm wavelength) and an increased absorbance in the bilirubin/β-carotene absorption region (450-490 nm wavelength). A change in absorbance in the visible and NIR wavelengths is a promising, additional measure of genital skin health related to menopause and vulvovaginal atrophy.
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Affiliation(s)
- Miranda A Farage
- Corporate Function R&D, The Procter & Gamble Company, Cincinnati, OH, USA
- Corporate Function R&D, The Procter & Gamble Company, Mason, OH, USA
| | - Tom Cambron
- Corporate Function R&D, The Procter & Gamble Company, Cincinnati, OH, USA
- Corporate Function R&D, The Procter & Gamble Company, Mason, OH, USA
| | - Kan-Zhi Liu
- Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, MB, Canada
- Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada
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Van Keer K, Van Keer J, Barbosa Breda J, Nassiri V, De Deyne C, Genbrugge C, Abegão Pinto L, Stalmans I, Vandewalle E. Non-invasive assessment of cerebral oxygenation: A comparison of retinal and transcranial oximetry. PLoS One 2018; 13:e0190612. [PMID: 29304150 PMCID: PMC5755852 DOI: 10.1371/journal.pone.0190612] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/18/2017] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND To investigate the correlation between cerebral (SO2-transcranial), retinal arterial (SaO2-retinal) and venous (SvO2-retinal) oxygen saturation as measured by near-infrared spectroscopy (NIRS) and retinal oximetry respectively. METHODS Paired retinal and cerebral oxygen saturation measurements were performed in healthy volunteers. Arterial and venous retinal oxygen saturation and diameter were measured using a non-invasive spectrophotometric retinal oximeter. Cerebral oxygen saturation was measured using near-infrared spectroscopy. Correlations between SO2-transcranial and retinal oxygen saturation and diameter measurements were assessed using Pearson correlation coefficients. Lin's concordance correlation coefficient (CCC) and Bland-Altman analysis were performed to evaluate the agreement between SO2-transcranial as measured by NIRS and as estimated using a fixed arterial:venous ratio as 0.3 x SaO2-retinal + 0.7 x SvO2-retinal. The individual relative weight of SaO2-retinal and SvO2-retinal to obtain the measured SO2-transcranial was calculated for all subjects. RESULTS Twenty-one healthy individuals aged 26.4 ± 2.2 years were analyzed. SO2-transcranial was positively correlated with both SaO2-retinal and SvO2-retinal (r = 0.44, p = 0.045 and r = 0.43, p = 0.049 respectively) and negatively correlated with retinal venous diameter (r = -0.51, p = 0.017). Estimated SO2-transcranial based on retinal oximetry showed a tolerance interval of (-13.70 to 14.72) and CCC of 0.46 (95% confidence interval: 0.05 to 0.73) with measured SO2-transcranial. The average relative weights of SaO2-retinal and SvO2-retinal to obtain SO2-transcranial were 0.31 ± 0.11 and 0.69 ± 0.11, respectively. CONCLUSION This is the first study to show the correlation between retinal and cerebral oxygen saturation, measured by NIRS and retinal oximetry. The average relative weight of arterial and venous retinal oxygen saturation to obtain the measured transcranial oxygen saturation as measured by NIRS, approximates the established arterial:venous ratio of 30:70 closely, but shows substantial inter-individual variation. These findings provide a proof of concept for the role of retinal oximetry in evaluating cerebral oxygenation.
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Affiliation(s)
- Karel Van Keer
- Department of Ophthalmology, University Hospitals Leuven, Leuven, Belgium
| | - Jan Van Keer
- Department of Cardiology, University Hospitals Leuven, Leuven, Belgium
| | - João Barbosa Breda
- Department of Ophthalmology, University Hospitals Leuven, Leuven, Belgium
| | | | - Cathy De Deyne
- Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium
- Department of Anesthesiology, Intensive Care, Emergency Medicine and Pain Therapy, Ziekenhuis Oost-Limburg, Genk, Belgium
| | - Cornelia Genbrugge
- Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium
- Department of Anesthesiology, Intensive Care, Emergency Medicine and Pain Therapy, Ziekenhuis Oost-Limburg, Genk, Belgium
| | - Luís Abegão Pinto
- Department of Ophthalmology, Centro Hospitalar Lisboa Norte, Lisbon, Portugal
| | - Ingeborg Stalmans
- Department of Ophthalmology, University Hospitals Leuven, Leuven, Belgium
- Department of Ophthalmology Neurosciences, Laboratory of Ophthalmology, KU Leuven, Leuven, Belgium
| | - Evelien Vandewalle
- Department of Ophthalmology, University Hospitals Leuven, Leuven, Belgium
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Chen H, Lin H, Chen W, Zhang B, Xiang W, Gao Q, Chen W, Liu Y. Preoperative and postoperative measurements of retinal vessel oxygen saturation in patients with different grades of cataracts. Acta Ophthalmol 2017; 95:e436-e442. [PMID: 27864880 DOI: 10.1111/aos.13332] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 10/14/2016] [Indexed: 01/02/2023]
Abstract
PURPOSE To assess the retinal vessel blood oxygen saturation preoperatively and postoperatively in patients with different grades of cataracts. METHODS This study included 40 eyes from 40 patients with senile cataracts ranging from grade 1 to 3. All 40 eyes received standard phacoemulsification and intraocular lens implantation. The mean retinal arterial and venular oxygen saturation (SO2 ) levels were measured using the Oxymap system prior to, immediately after and 3 months after cataract surgery. The arterial-venular difference (AVD) was calculated as the difference between the arterial and venular saturations. Linear regression analysis was performed to identify the relationship between the lens density grades and changes in the measured retina vessel SO2 . RESULTS The mean age of the subjects was 64.1 ± 7.8 years, and 14 (35%) were male. The mean SO2 level increased in the retinal arterioles from 90.5 ± 7.8% to 95.0 ± 6.7% immediately postoperatively and to 98.3 ± 5.3% at 3 months after surgery (p < 0.001). The mean venular saturation levels were 43.4 ± 9.7%, 58.0 ± 8.5% and 61.9 ± 6.5% at baseline, immediately after and at 3 months postoperatively, respectively, with a statistically significant increase after surgery (p < 0.001). The mean AVD significantly decreased from 47.1 ± 8.9% before surgery to 37.1 ± 7.3% immediately after and 36.4 ± 6.4% 3 months after surgery (p < 0.02). A linear regression model indicated that denser lens opacity was significantly associated with a larger amplitude of the venular SO2 level and the AVD after cataract surgery: change of venous SO2 = 5.934-0.191 × Age + 13.534 × Lens Grade (age: p = 0.586; lens grade: p < 0.001); change in AVD = -7.438-0.037 × Age + 7.744 × Lens Grade (age: p = 0.917; lens grade: p = 0.031). CONCLUSIONS Retinal arterial and venular oxygen saturation levels are significantly increased after cataract surgery, and increase rates vary with the preoperative grading of lens density.
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Affiliation(s)
- Hui Chen
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Haotian Lin
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Wan Chen
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Bo Zhang
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Wu Xiang
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Qianying Gao
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Weirong Chen
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
| | - Yizhi Liu
- State Key Laboratory of Ophthalmology; Zhongshan Ophthalmic Center; Sun Yat-sen University; Guangzhou Guangdong China
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van der Putten MA, MacKenzie LE, Davies AL, Fernandez-Ramos J, Desai RA, Smith KJ, Harvey AR. A multispectral microscope for in vivo oximetry of rat dorsal spinal cord vasculature. Physiol Meas 2016; 38:205-218. [PMID: 28001129 DOI: 10.1088/1361-6579/aa5527] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Quantification of blood oxygen saturation (SO2) in vivo is essential for understanding the pathogenesis of diseases in which hypoxia is thought to play a role, including inflammatory disorders such as multiple sclerosis (MS) and rheumatoid arthritis (RA). We describe a low-cost multispectral microscope and oximetry technique for calibration-free absolute oximetry of surgically exposed blood vessels in vivo. We imaged the vasculature of the dorsal spinal cord in healthy rats, and varied inspired oxygen (FiO2) in order to evaluate the sensitivity of the imaging system to changes in SO2. The venous SO2 was calculated as 67.8 ± 10.4% (average ± standard deviation), increasing to 83.1 ± 11.6% under hyperoxic conditions (100% FiO2) and returning to 67.4 ± 10.9% for a second normoxic period; the venous SO2 was 50.9 ± 15.5% and 29.2 ± 24.6% during subsequent hypoxic states (18% and 15% FiO2 respectively). We discuss the design and performance of our multispectral imaging system, and the future scope for extending this oximetry technique to quantification of hypoxia in inflamed tissue.
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Felder AE, Wanek J, Blair NP, Shahidi M. Inner Retinal Oxygen Extraction Fraction in Response to Light Flicker Stimulation in Humans. Invest Ophthalmol Vis Sci 2016; 56:6633-7. [PMID: 26469748 DOI: 10.1167/iovs.15-17321] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Light flicker has been shown to stimulate retinal neural activity, increase blood flow, and alter inner retinal oxygen metabolism (MO2) and delivery (DO2). The purpose of the study was to determine the change in MO2 relative to DO2 due to light flicker stimulation in humans, as assessed by the inner retinal oxygen extraction fraction (OEF). METHODS An optical imaging system, based on a modified slit lamp biomicroscope, was developed for simultaneous measurements of retinal vascular diameter (D) and oxygen saturation (SO2). Retinal images were acquired in 20 healthy subjects before and during light flicker stimulation. Arterial and venous D (DA and DV) and SO2 (SO2A and SO2V) were quantified within a circumpapillary region. Oxygen extraction fraction was defined as the ratio of MO2 to DO2 and was calculated as (SO2A - SO2V)/SO2A. Reproducibility of measurements was assessed. RESULTS Coefficients of variation and intraclass correlation coefficients of repeated measurements were <5% and ≥0.83, respectively. During light flicker stimulation, DA, DV , and SO2V significantly increased (P ≤ 0.004). Oxygen extraction fraction was 0.37 ± 0.08 before light flicker and significantly decreased to 0.31 ± 0.07 during light flicker (P = 0.001). CONCLUSIONS Oxygen extraction fraction before and during light flicker stimulation is reported in human subjects for the first time. Oxygen extraction fraction decreased during light flicker stimulation, indicating the change in DO2 exceeded that of MO2. This technology is potentially useful for the detection of changes in OEF response to light flicker in physiological and pathological retinal conditions.
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Bartels K, Thiele RH. Advances in photoplethysmography: beyond arterial oxygen saturation. Can J Anaesth 2015; 62:1313-28. [PMID: 26286382 DOI: 10.1007/s12630-015-0458-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 07/03/2015] [Accepted: 08/11/2015] [Indexed: 01/19/2023] Open
Abstract
PURPOSE Photoplethysmography permits continuous measurement of heart rate and peripheral oxygen saturation and has been widely used to inform clinical decisions. Recently, a myriad of noninvasive hemodynamic monitoring devices using this same technology have been increasingly available. This narrative review aims to summarize the principles that form the basis for the function of these devices as well as to comment on trials evaluating their accuracy and clinical application. PRINCIPAL FINDINGS Advanced monitoring devices extend photoplethysmography technology beyond measuring oxygen concentration and heart rate. Quantification of respiratory variation of the photoplethysmographic waveform reflects respiratory variation of the arterial pressure waveform and can be used to gauge volume responsiveness. Both the volume-clamp and physiocal techniques are extensions of conventional photoplethysmography and permit continuous measurement of finger arterial blood pressure. Finger arterial pressure waveforms can subsequently inform estimations of cardiac output. CONCLUSIONS Although respiratory variations of the plethysmographic waveform correlate only modestly with the arterial blood pressure waveform, fluid responsiveness can be relatively consistently assessed using both approaches. Continuous blood pressure measurements obtained using the volume-clamp technique may be as accurate as conventional brachial noninvasive blood pressure measurements. Most importantly, clinical comparative effectiveness studies are still needed in order to determine if these technologies can be translated into improvement of relevant patient outcomes.
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Affiliation(s)
- Karsten Bartels
- Departments of Anesthesiology and Surgery, University of Colorado Denver, Aurora, CO, USA
| | - Robert H Thiele
- Divisions of Cardiac, Thoracic, and Critical Care Anesthesiology, Departments of Anesthesiology and Biomedical Engineering, University of Virginia School of Medicine, Charlottesville, VA, USA.
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