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Khoobehi B, Wafapoor H, Eaton A, Liu R, Firn K, Kubilay T. Noninvasive Measurement of Oxygen Saturation in Human Retinal Blood Vessels and Tissues With Multispectral Confocal Imaging. Ophthalmic Surg Lasers Imaging Retina 2022; 53:275-283. [PMID: 35575738 DOI: 10.3928/23258160-20220420-01] [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: 11/20/2022]
Abstract
BACKGROUND AND OBJECTIVE Proof of concept for the first system of noninvasive human retinal vessel and tissue oxygenation measurement in axial and radial directions. MATERIALS AND METHODS A confocal imaging system capable of calculating and mapping relative retinal blood oxygenation in radial and axial directions from three eyes of two healthy subjects was built. The relationship between oxygenation and retinal depth in vivo was analyzed to illustrate application of this novel system. RESULTS The system shows capacity for measuring oxygenation along retinal depth for the first time. (1) Arteriovenous oxygenation difference decreases with blood vessel diameter. (2) Artery-tissue oxygenation difference is greater than vein-tissue oxygenation difference in the same region. (3) Intravascular-extravascular oxygenation difference decreases with blood vessel diameter. (4) Oxygenation data reported with a 95% CI are as follows: A1 91.5% ± 18.2%, V1 32.8% ± 18.6%, A2 97.3% ± 17.8%, V2 64.4% ± 11.2%, A3 73.2% ± 19.1%, V3 52.9% ± 15.3%, and Tissue 56.6% ± 00.4%. CONCLUSION This article demonstrates proof of concept for retinal oxygenation calculation in radial and axial dimensions for the first time. Initial results provide biological validity to this method. Future aims include further characterization of this system's results in healthy subjects and subsequent comparison of oxygenation between diseased and healthy retinae. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:275-283.].
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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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Lu Y, Hu D, Ying W. A fast numerical method for oxygen supply in tissue with complex blood vessel network. PLoS One 2021; 16:e0247641. [PMID: 33635924 PMCID: PMC7909958 DOI: 10.1371/journal.pone.0247641] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 02/10/2021] [Indexed: 11/20/2022] Open
Abstract
Angiogenesis plays an essential role in many pathological processes such as tumor growth, wound healing, and keloid development. Low oxygen level is the main driving stimulus for angiogenesis. In an animal tissue, the oxygen level is mainly determined by three effects—the oxygen delivery through blood flow in a refined vessel network, the oxygen diffusion from blood to tissue, and the oxygen consumption in cells. Evaluation of the oxygen field is usually the bottleneck in large scale modeling and simulation of angiogenesis and related physiological processes. In this work, a fast numerical method is developed for the simulation of oxygen supply in tissue with a large-scale complex vessel network. This method employs an implicit finite-difference scheme to compute the oxygen field. By virtue of an oxygen source distribution technique from vessel center lines to mesh points and a corresponding post-processing technique that eliminate the local numerical error induced by source distribution, square mesh with relatively large mesh sizes can be applied while sufficient numerical accuracy is maintained. The new method has computational complexity which is slightly higher than linear with respect to the number of mesh points and has a convergence order which is slightly lower than second order with respect to the mesh size. With this new method, accurate evaluation of the oxygen field in a fully vascularized tissue on the scale of centimeter becomes possible.
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Affiliation(s)
- Yuankai Lu
- School of Mathematical Sciences, Institute of Natural Sciences, and MOE-LSC, Shanghai Jiao Tong University, Shanghai, China
| | - Dan Hu
- School of Mathematical Sciences, Institute of Natural Sciences, and MOE-LSC, Shanghai Jiao Tong University, Shanghai, China
- * E-mail:
| | - Wenjun Ying
- School of Mathematical Sciences, Institute of Natural Sciences, and MOE-LSC, Shanghai Jiao Tong University, Shanghai, China
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Srinivasan VJ, Moshiri A. Imaging oxygenation of retinal capillaries with depth resolution. Proc Natl Acad Sci U S A 2020; 117:14626-14628. [PMID: 32554605 PMCID: PMC7334518 DOI: 10.1073/pnas.2008404117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Vivek J Srinivasan
- Biomedical Engineering Department, University of California, Davis, CA 95616;
- Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, CA 95817
| | - Ala Moshiri
- Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, CA 95817
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Şencan İ, Esipova TV, Yaseen MA, Fu B, Boas DA, Vinogradov SA, Shahidi M, Sakadžić S. Two-photon phosphorescence lifetime microscopy of retinal capillary plexus oxygenation in mice. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-9. [PMID: 30516039 PMCID: PMC6278707 DOI: 10.1117/1.jbo.23.12.126501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 11/07/2018] [Indexed: 05/23/2023]
Abstract
Impaired oxygen delivery and/or consumption in the retinal tissue underlies the pathophysiology of many retinal diseases. However, the essential tools for measuring oxygen concentration in retinal capillaries and studying oxygen transport to retinal tissue are still lacking. We show that two-photon phosphorescence lifetime microscopy can be used to map absolute partial pressures of oxygen (pO2) in the retinal capillary plexus. Measurements were performed at various retinal depths in anesthetized mice under systemic normoxic and hyperoxic conditions. We used a newly developed two-photon phosphorescent oxygen probe, based on a two-photon absorbing platinum tetraphthalimidoporphyrin, and commercially available optics without correction for optical aberrations of the eye. The transverse and axial distances within the tissue volume were calibrated using a model of the eye's optical system. We believe this is the first demonstration of in vivo depth-resolved imaging of pO2 in retinal capillaries. Application of this method has the potential to advance our understanding of oxygen delivery on the microvascular scale and help elucidate mechanisms underlying various retinal diseases.
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Affiliation(s)
- İkbal Şencan
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Tatiana V. Esipova
- University of Pennsylvania, Departments of Biochemistry and Biophysics and of Chemistry, Philadelphia, Pennsylvania, United States
| | - Mohammad A. Yaseen
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Buyin Fu
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - David A. Boas
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
- Boston University, Department of Biomedical Engineering, Boston, Massachusetts, United States
| | - Sergei A. Vinogradov
- University of Pennsylvania, Departments of Biochemistry and Biophysics and of Chemistry, Philadelphia, Pennsylvania, United States
| | - Mahnaz Shahidi
- University of Southern California, Departments of Ophthalmology and Biomedical Engineering, Los Angeles, California, United States
| | - Sava Sakadžić
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
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Blair NP, Tan MR, Felder AE, Teng PY, Wanek J, Shahidi M. Retinal tissue oxygen tension and consumption during light flicker stimulation in rat. Exp Eye Res 2018; 175:207-211. [PMID: 30121195 DOI: 10.1016/j.exer.2018.08.007] [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: 04/13/2018] [Revised: 08/09/2018] [Accepted: 08/12/2018] [Indexed: 10/28/2022]
Abstract
Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light flicker stimulation of various durations alters the depth profile metrics of oxygen partial pressure in the retinal tissue (tPO2) but not the outer retinal oxygen consumption rate (QO2). In 17 rats, tPO2 depth profiles were derived by phosphorescence lifetime imaging after intravitreal injection of an oxyphor. tPO2 profile metrics, including mean inner retinal tPO2, maximum outer retinal tPO2 and minimum outer retinal tPO2 were determined. QO2 was calculated using a one-dimensional oxygen diffusion model. Data were acquired at baseline (constant light illumination) and during light flicker stimulation at 10 Hz under the same mean illumination levels, and differences between values obtained during flicker and baseline were calculated. None of the tPO2 profile metrics or QO2 differences depended on the duration of light flicker stimulation (R2 ≤ 0.03). No significant change in any of the tPO2 profile metrics was detected with light flicker compared with constant light (P ≥ 0.08). Light flicker decreased QO2 from 0.53 ± 0.29 to 0.38 ± 0.30 mL O2/(min*100 gm), a reduction of 28% (P = 0.02). The retinal compensatory responses to the physiologic challenge of light flicker stimulation were effective in maintaining the levels of oxygen at or near baseline in the inner retina. Oxygen availability to the inner retina during light flicker may also have been enhanced by the decrease in QO2.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Michael R Tan
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Anthony E Felder
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Pang-Yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
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Papkovsky DB, Dmitriev RI. Imaging of oxygen and hypoxia in cell and tissue samples. Cell Mol Life Sci 2018; 75:2963-2980. [PMID: 29761206 PMCID: PMC11105559 DOI: 10.1007/s00018-018-2840-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 04/24/2018] [Accepted: 05/07/2018] [Indexed: 01/17/2023]
Abstract
Molecular oxygen (O2) is a key player in cell mitochondrial function, redox balance and oxidative stress, normal tissue function and many common disease states. Various chemical, physical and biological methods have been proposed for measurement, real-time monitoring and imaging of O2 concentration, state of decreased O2 (hypoxia) and related parameters in cells and tissue. Here, we review the established and emerging optical microscopy techniques allowing to visualize O2 levels in cells and tissue samples, mostly under in vitro and ex vivo, but also under in vivo settings. Particular examples include fluorescent hypoxia stains, fluorescent protein reporter systems, phosphorescent probes and nanosensors of different types. These techniques allow high-resolution mapping of O2 gradients in live or post-mortem tissue, in 2D or 3D, qualitatively or quantitatively. They enable control and monitoring of oxygenation conditions and their correlation with other biomarkers of cell and tissue function. Comparison of these techniques and corresponding imaging setups, their analytical capabilities and typical applications are given.
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Affiliation(s)
- Dmitri B Papkovsky
- School of Biochemistry and Cell Biology, University College Cork, Cavanagh Pharmacy Building, College Road, Cork, Ireland.
| | - Ruslan I Dmitriev
- School of Biochemistry and Cell Biology, University College Cork, Cavanagh Pharmacy Building, College Road, Cork, Ireland.
- Institute for Regenerative Medicine, Sechenov University, Moscow, Russian Federation.
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Akiyama H, Takahashi I, Shimoda Y, Mukai R, Yoshihara T, Tobita S. Ir(iii) complex-based oxygen imaging of living cells and ocular fundus with a gated ICCD camera. Photochem Photobiol Sci 2018; 17:846-853. [PMID: 29808210 DOI: 10.1039/c8pp00122g] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Phosphorescence lifetime imaging methods using oxygen-sensitive probes are very useful for visualizing the oxygen status of living cells and tissues with high spatial resolution. We aim to develop a useful oxygen detection technique combining a phosphorescent oxygen probe and an optimal detection method. Herein we present a biological oxygen imaging method using a microscope equipped with a gated intensified charge-coupled device (ICCD) camera as a detector and an Ir(iii) complex as a phosphorescent oxygen probe. Microscopic luminescence images of monolayer HT-29 cells (human colorectal adenocarcinoma cells) obtained using the cell-penetrating Ir(iii) complex BTPDM1 and an inverted microscope demonstrated that this method allowed visualization of the oxygen gradient produced in a monolayer of cultured cells when the monolayer is covered with a thin coverslip. Furthermore, combining the IR-emitting Ir(iii) complex DTTPH-PEG24 with a macrozoom microscope equipped with a gated ICCD camera enabled both the visualization of retinal vessels near the optic disc and the monitoring of oxygen level changes in a rabbit retina upon changing the inhaled oxygen content.
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Affiliation(s)
- H Akiyama
- Department of Ophthalmology and Medicine and Biological Science, Graduate School of Medicine, Gunma University, Showa-machi, Maebashi, Gunma 371-8512, Japan
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The effect of autoimmune retinopathy on retinal vessel oxygen saturation. Eye (Lond) 2018; 32:1455-1462. [PMID: 29786086 DOI: 10.1038/s41433-018-0122-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 02/28/2018] [Indexed: 01/16/2023] Open
Abstract
PURPOSE To study the retinal vessel oxygen saturation alterations in patients with autoimmune retinopathy (AIR) and patients with autoimmune retinopathy associated with retinitis pigmentosa (AIR-RP) in comparison with healthy controls and patients with isolated retinitis pigmentosa (RP). DESIGN Prospective, cross-sectional, and non-interventional study. SUBJECTS Retinal vessel oximetry (RO) was performed on a total of 139 eyes: six eyes suffering from AIR and four eyes with AIR-RP were compared to 59 healthy control eyes and to 70 eyes with RP. METHODS A computer-based program of the retinal vessel analyser unit (IMEDOS Systems UG, Jena, Germany) was used to evaluate retinal vessel oxygen saturation. The mean oxygen saturation in the first and second branch retinal arterioles (A-SO2) and venules (V-SO2) were measured and their difference (A-V SO2) was calculated. In addition, we measured the diameter of the retinal arterioles (D-A) and venules (D-V). MAIN OUTCOME MEASURES Oxygen metabolism is altered in patients with isolated AIR and AIR-RP. RESULTS Both, AIR and AIR-RP groups, differed from healthy controls showing significantly higher V-SO2 values and significantly lower A-V SO2 values (p < 0.025). In addition, the AIR-RP group could be differentiated from eyes suffering from isolated RP by means of significantly higher V-SO2 values. Comparing retinal vessel diameters, both, the AIR and AIR-RP groups, presented with significant arterial (p = 0.05) and venular (p < 0.03) vessel attenuation than the healthy control group. CONCLUSIONS Based on our results, in analogy to patients suffering from RP, oxygen metabolism seems to be altered in AIR patients.
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Felder AE, Wanek J, Teng PY, Blair NP, Shahidi M. A method for volumetric retinal tissue oxygen tension imaging. Curr Eye Res 2017; 43:122-127. [PMID: 28956656 DOI: 10.1080/02713683.2017.1373823] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Inadequate retinal oxygenation occurs in many vision-threatening retinal diseases, including diabetic retinopathy, retinal vascular occlusions, and age-related macular degeneration. Therefore, techniques that assess retinal oxygenation are necessary to understand retinal physiology in health and disease. The purpose of the current study is to report a method for the three-dimensional (3D) imaging of retinal tissue oxygen tension (tPO2) in rats. METHODS Imaging was performed in Long Evans pigmented rats under systemic normoxia (N = 6) or hypoxia (N = 3). A vertical laser line was horizontally scanned on the retina and a series of optical section phase-delayed phosphorescence images were acquired. From these images, phosphorescence volumes at each phase delay were constructed and a 3D retinal tPO2 volume was generated. Retinal tPO2 volumes were quantitatively analyzed by generating retinal depth profiles of mean tPO2 (MtPO2) and the spatial variation of tPO2 (SVtPO2). The effects of systemic condition (normoxia/hypoxia) and retinal depth on MtPO2 and SVtPO2 were determined by mixed linear model. RESULTS Each 3D retinal tPO2 volume was approximately 500 × 750 × 200 μm (horizontal × vertical × depth) and consisted of 45 en face tPO2 images through the retinal depth. MtPO2 at the chorioretinal interface was significantly correlated with systemic arterial oxygen tension (P = 0.007; N = 9). There were significant effects of both systemic condition and retinal depth on MtPO2 and SVtPO2, such that both were lower under hypoxia than normoxia and higher in the outer retina than inner retina (P < 0.001). CONCLUSION For the first time, 3D imaging of retinal tPO2 was demonstrated, with potential future application for assessment of physiological alterations in animal models of retinal diseases.
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Affiliation(s)
- Anthony E Felder
- a Department of Bioengineering , University of Illinois at Chicago , Chicago IL, USA.,b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Justin Wanek
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Pang-Yu Teng
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Norman P Blair
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Mahnaz Shahidi
- c Department of Ophthalmology , University of Southern California , Los Angeles CA, USA
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A Method for Combined Retinal Vascular and Tissue Oxygen Tension Imaging. Sci Rep 2017; 7:10622. [PMID: 28878307 PMCID: PMC5587610 DOI: 10.1038/s41598-017-10955-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 08/17/2017] [Indexed: 11/17/2022] Open
Abstract
The retina requires adequate oxygenation to maintain cellular metabolism and visual function. Inner retinal oxygen metabolism is directly related to retinal vascular oxygen tension (PO2) and inner retinal oxygen extraction fraction (OEF), whereas outer retinal oxygen consumption (QO2) relies on oxygen availability by the choroid and is contingent upon retinal tissue oxygen tension (tPO2) gradients across the retinal depth. Thus far, these oxygenation and metabolic parameters have been measured independently by different techniques in separate animals, precluding a comprehensive and correlative assessment of retinal oxygenation and metabolism dynamics. The purpose of the current study is to report an innovative optical system for dual oxyphor phosphorescence lifetime imaging to near-simultaneously measure retinal vascular PO2 and tPO2 in rats. The use of a new oxyphor with different spectral characteristics allowed differentiation of phosphorescence signals from the retinal vasculature and tissue. Concurrent measurements of retinal arterial and venous PO2, tPO2 through the retinal depth, inner retinal OEF, and outer retinal QO2 were demonstrated, permitting a correlative assessment of retinal oxygenation and metabolism. Future application of this method can be used to investigate the relations among retinal oxygen content, extraction and metabolism under pathologic conditions and thus advance knowledge of retinal hypoxia pathophysiology.
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Linsenmeier RA, Zhang HF. Retinal oxygen: from animals to humans. Prog Retin Eye Res 2017; 58:115-151. [PMID: 28109737 DOI: 10.1016/j.preteyeres.2017.01.003] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 01/13/2017] [Accepted: 01/17/2017] [Indexed: 10/20/2022]
Abstract
This article discusses retinal oxygenation and retinal metabolism by focusing on measurements made with two of the principal methods used to study O2 in the retina: measurements of PO2 with oxygen-sensitive microelectrodes in vivo in animals with a retinal circulation similar to that of humans, and oximetry, which can be used non-invasively in both animals and humans to measure O2 concentration in retinal vessels. Microelectrodes uniquely have high spatial resolution, allowing the mapping of PO2 in detail, and when combined with mathematical models of diffusion and consumption, they provide information about retinal metabolism. Mathematical models, grounded in experiments, can also be used to simulate situations that are not amenable to experimental study. New methods of oximetry, particularly photoacoustic ophthalmoscopy and visible light optical coherence tomography, provide depth-resolved methods that can separate signals from blood vessels and surrounding tissues, and can be combined with blood flow measures to determine metabolic rate. We discuss the effects on retinal oxygenation of illumination, hypoxia and hyperoxia, and describe retinal oxygenation in diabetes, retinal detachment, arterial occlusion, and macular degeneration. We explain how the metabolic measurements obtained from microelectrodes and imaging are different, and how they need to be brought together in the future. Finally, we argue for revisiting the clinical use of hyperoxia in ophthalmology, particularly in retinal arterial occlusions and retinal detachment, based on animal research and diffusion theory.
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Affiliation(s)
- Robert A Linsenmeier
- Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Neurobiology Department, Northwestern University, 2205 Tech Drive, Evanston 60208-3520, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA.
| | - Hao F Zhang
- Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA.
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Todorova MG, Türksever C, Schötzau A, Schorderet DF, Valmaggia C. Metabolic and functional changes in retinitis pigmentosa: comparing retinal vessel oximetry to full-field electroretinography, electrooculogram and multifocal electroretinography. Acta Ophthalmol 2016; 94:e231-41. [PMID: 26490228 DOI: 10.1111/aos.12846] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 08/03/2015] [Indexed: 11/30/2022]
Abstract
PURPOSE To determine a relationship between the retinal vessel saturation alterations and the residual retinal function measured by means of full-field electroretinography (full-field ERG), electrooculogram (EOG) and multifocal electroretinography (mfERG) in patients with retinitis pigmentosa (RP). METHODS Retinal vessel oximetry (RO), full-field ERG, EOG and mfERG were performed on 43 eyes of 22 patients suffering from RP and were compared to those of 26 eyes of 13 healthy controls. The oxygen saturation in the first and second branch retinal arterioles (A-SO2 ) and venules (V-SO2 ) was measured, and their difference (A-V SO2 ) was calculated. Full-field ERG amplitudes, EOG parameters and averaged mfERG response amplitudes (within central 3°, between 3° and 8°, 8° and 15°, 15° and 24°) were evaluated in relation to the RO measurements. RESULTS V-SO2 correlated negatively with the full-field ERG and EOG values, with increasing functional damage the V-SO2 was higher. The RP group was well distinguished from the controls when the RO measurements were correlated to the averaged N1 (baseline to trough), but also to the N1P1 (trough-to-peak) mfERG response amplitudes. Receiver operating characteristic (ROC) curve of V-SO2 , compared to those of N1 and N1P1 mfERG response averages (15-24°), presented a high differential margin between RP and controls (p < 0.001), shown by an area under the ROC curve of 0.912 (95% CI: 0.840-0.984). CONCLUSION Retinal vessel saturation showed a significant relation to full-field ERG, EOG and mfERG. Thus, retinal vessel oximetry could potentially complement electrophysiological tests in monitoring disease progression in patients with RP.
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Affiliation(s)
| | - Cengiz Türksever
- Department of Ophthalmology; University of Basel; Basel Switzerland
| | - Andreas Schötzau
- Department of Ophthalmology; University of Basel; Basel Switzerland
| | - Daniel F. Schorderet
- IRO- Institute for Research in Ophthalmology; Sion Switzerland
- Department of Ophthalmology; University of Lausanne; Lausanne Switzerland
- School of Life Sciences; Federal Institute of Technology; Lausanne Switzerland
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Yang F, Yang CH, Wang FM, Cheng YT, Teng CC, Lee LJ, Yang CH, Fan LS. A high-density microelectrode-tissue-microelectrode sandwich platform for application of retinal circuit study. Biomed Eng Online 2015; 14:109. [PMID: 26611649 PMCID: PMC4662037 DOI: 10.1186/s12938-015-0106-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 11/23/2015] [Indexed: 01/05/2023] Open
Abstract
Background Microelectrode array (MEA) devices are frequently used in neural circuit studies, especially in retinal prosthesis. For a high throughput stimulation and recording paradigm, it is desirable to obtain the responses of multiple surface RGCs initiated from the electrical signals delivered to multiple photoreceptor cells. This can be achieved by an high density MEA-tissue-MEA (MTM) sandwich configuration. However, the retina is one of the most metabolically active tissues, consumes oxygen as rapidly as the brain. The major concern of the MTM configuration is the supply of oxygen. Methods We aimed to develop a high density MTM sandwich platform which consists of stacks of a stimulation MEA, retinal tissue and a recording MEA. Retina is a metabolically active tissue and the firing rate is very sensitive to oxygen level. We designed, simulated and microfabricated porous high density MEAs and an adjustable perfusion system that electrical signals can be delivered to and recorded from the clipped retinal tissue. Results The porous high-density MEAs linked with stimulation or recording devices within a perfusion system were manufactured and the MTM platform was assembled with a retina slice inside. The firing rate remained constant between 25 and 55 min before dramatically declined, indicating that within certain period of time (e.g. 30 min after habituation), the retina condition was kept by sufficient oxygen supply via the perfusion holes in the MEAs provided by the double perfusion system. Conclusions MTM sandwich structure is an efficient platform to study the retinal neural circuit. The material and arrangement of high density microelectrodes with porous design make this MEA appropriate for sub-retina prosthesis. Finding ways to prolong the recording time and reduce the signal-to-noise ratio are important to improve our MTM prototype.
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Affiliation(s)
- Frank Yang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Chung-Hua Yang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Fu-Min Wang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Ya-Ting Cheng
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Chih-Ciao Teng
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Li-Jen Lee
- Graduated Institute of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan
| | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan
| | - Long-Sheng Fan
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan.
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Yi J, Liu W, Chen S, Backman V, Sheibani N, Sorenson CM, Fawzi AA, Linsenmeier RA, Zhang HF. Visible light optical coherence tomography measures retinal oxygen metabolic response to systemic oxygenation. LIGHT, SCIENCE & APPLICATIONS 2015; 4:e334. [PMID: 26658555 PMCID: PMC4674267 DOI: 10.1038/lsa.2015.107] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The lack of capability to quantify oxygen metabolism noninvasively impedes both fundamental investigation and clinical diagnosis of a wide spectrum of diseases including all the major blinding diseases such as age-related macular degeneration, diabetic retinopathy, and glaucoma. Using visible light optical coherence tomography (vis-OCT), we demonstrated accurate and robust measurement of retinal oxygen metabolic rate (rMRO2) noninvasively in rat eyes. We continuously monitored the regulatory response of oxygen consumption to a progressive hypoxic challenge. We found that both oxygen delivery, and rMRO2 increased from the highly regulated retinal circulation (RC) under hypoxia, by 0.28 ± 0.08 μL min-1 (p < 0.001), and 0.20 ± 0.04 μL min-1 (p < 0.001) per 100 mmHg systemic pO2 reduction, respectively. The increased oxygen extraction compensated for the deficient oxygen supply from the poorly regulated choroidal circulation. Results from an oxygen diffusion model based on previous oxygen electrode measurements corroborated our in vivo observations. We believe that vis-OCT has the potential to reveal the fundamental role of oxygen metabolism in various retinal diseases.
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Affiliation(s)
- Ji Yi
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Wenzhong Liu
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Siyu Chen
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Nader Sheibani
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI 53705, USA
| | - Christine M Sorenson
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI 53705, USA
| | - Amani A Fawzi
- Department of Ophthalmology, Northwestern University, Chicago Illinois 60611, USA
| | - Robert A Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA ; Department of Ophthalmology, Northwestern University, Chicago Illinois 60611, USA ; Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA
| | - Hao F Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA ; Department of Ophthalmology, Northwestern University, Chicago Illinois 60611, USA
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Nanoengineering of therapeutics for retinal vascular disease. Eur J Pharm Biopharm 2015; 95:323-30. [PMID: 26022642 DOI: 10.1016/j.ejpb.2015.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Revised: 04/29/2015] [Accepted: 05/05/2015] [Indexed: 01/07/2023]
Abstract
Retinal vascular diseases, including diabetic retinopathy, neovascular age related macular degeneration, and retinal vein occlusion, are leading causes of blindness in the Western world. These diseases share several common disease mechanisms, including vascular endothelial growth factor (VEGF) signaling, hypoxia, and inflammation, which provide opportunities for common therapeutic strategies. Treatment of these diseases using laser therapy, anti-VEGF injections, and/or steroids has significantly improved clinical outcomes. However, these strategies do not address the underlying root causes of pathology, and may have deleterious side effects. Furthermore, many patients continue to progress toward legal blindness despite receiving regular therapy. Nanomedicine, the engineering of therapeutics at the 1-100 nm scale, is a promising approach for improving clinical management of retinal vascular diseases. Nanomedicine-based technologies have the potential to revolutionize the treatment of ophthalmology, through enabling sustained release of drugs over several months, reducing side effects due to specific targeting of dysfunctional cells, and interfacing with currently "undruggable" targets. We will discuss emerging nanomedicine-based applications for the treatment of complications associated with retinal vascular diseases, including angiogenesis and inflammation.
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Noninvasive assessment of retinal vascular oxygen content among normal and diabetic human subjects: a study using hyperspectral computed tomographic imaging spectroscopy. Retina 2015; 34:1854-60. [PMID: 24732694 DOI: 10.1097/iae.0000000000000146] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE This pilot study was aimed to demonstrate the clinical feasibility of using hyperspectral computed tomographic spectroscopy to measure blood oxygen content in human retinal vessels. METHODS All procedures were performed under a University of Southern California Institutional Review Board-approved protocol and after obtaining informed consent. Fifty-seven subjects with and without diabetic retinopathy were dilated for standard fundus photography. Fundus photographs and retinal vascular oxygen measurements (oximetry) were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a standard fundus camera. Oximetry measurements were made along arteries (Aox) and veins (Vox) within vessel segments that were 1 to 2 disk diameters from the optic disk. RESULTS For all control subjects (n = 45), mean Aox and Vox were 93 ± 7% and 65 ± 5% (P = 0.001), respectively. For all diabetic subjects (n = 12), mean Aox and Vox were 90 ± 7% and 68 ± 5% (P = 0.001), respectively. In subjects with proliferative diabetic retinopathy, Aox was significantly lower, and Vox was significantly higher than other groups (85 ± 4% and 71 ± 4%, respectively; P = 0.04, analysis of variance). There was a highly significant difference in the arteriovenous difference between subjects with proliferative diabetic retinopathy and those in the control group (14 vs. 26%, P = 0.003). CONCLUSION Hyperspectral computed tomographic spectroscopy is a clinically feasible method for measurement and analysis of vascular oxygen content in retinal health and disease. This study uses the techniques relevant to oximetry; however, the breadth of spectral data available through this method may be applicable to study other anatomical and functional features of the retina in health and disease.
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18
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Lloyd D, Williams CF. Avoid Excessive Oxygen Levels in Experiments with Organisms, Tissues and Cells. Adv Microb Physiol 2015; 67:293-314. [PMID: 26616520 DOI: 10.1016/bs.ampbs.2015.09.001] [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] [Indexed: 10/22/2022]
Abstract
O2 levels encountered in vivo in cells and tissues are almost always at least an order of magnitude less than atmospheric pO2 because of sensing, signalling and bioenergetic demand. Although deleterious reactions are minimized by protective mechanisms (residual toxic products scavenged and detoxified) ambient levels should be mimicked in experiments with whole organisms, their isolated organs, tissues or cells and also with cultures of cell lines. These are also important issues for microorganisms inhabiting low O2 niches within higher organisms and their cells. Here, we highlight the importance of optimization of micro-aerobic conditions for experimentation and the deleterious consequences of not doing so.
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Sekizuka T, Kai M, Nakanaga K, Nakata N, Kazumi Y, Maeda S, Makino M, Hoshino Y, Kuroda M. Complete genome sequence and comparative genomic analysis of Mycobacterium massiliense JCM 15300 in the Mycobacterium abscessus group reveal a conserved genomic island MmGI-1 related to putative lipid metabolism. PLoS One 2014; 9:e114848. [PMID: 25503461 PMCID: PMC4263727 DOI: 10.1371/journal.pone.0114848] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 11/14/2014] [Indexed: 12/30/2022] Open
Abstract
Mycobacterium abscessus group subsp., such as M. massiliense, M. abscessus sensu stricto and M. bolletii, are an environmental organism found in soil, water and other ecological niches, and have been isolated from respiratory tract infection, skin and soft tissue infection, postoperative infection of cosmetic surgery. To determine the unique genetic feature of M. massiliense, we sequenced the complete genome of M. massiliense type strain JCM 15300 (corresponding to CCUG 48898). Comparative genomic analysis was performed among Mycobacterium spp. and among M. abscessus group subspp., showing that additional ß-oxidation-related genes and, notably, the mammalian cell entry (mce) operon were located on a genomic island, M. massiliense Genomic Island 1 (MmGI-1), in M. massiliense. In addition, putative anaerobic respiration system-related genes and additional mycolic acid cyclopropane synthetase-related genes were found uniquely in M. massiliense. Japanese isolates of M. massiliense also frequently possess the MmGI-1 (14/44, approximately 32%) and three unique conserved regions (26/44; approximately 60%, 34/44; approximately 77% and 40/44; approximately 91%), as well as isolates of other countries (Malaysia, France, United Kingdom and United States). The well-conserved genomic island MmGI-1 may play an important role in high growth potential with additional lipid metabolism, extra factors for survival in the environment or synthesis of complex membrane-associated lipids. ORFs on MmGI-1 showed similarities to ORFs of phylogenetically distant M. avium complex (MAC), suggesting that horizontal gene transfer or genetic recombination events might have occurred within MmGI-1 among M. massiliense and MAC.
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Affiliation(s)
- Tsuyoshi Sekizuka
- Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan
- * E-mail: (TS); (YH)
| | - Masanori Kai
- Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Kazue Nakanaga
- Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Noboru Nakata
- Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yuko Kazumi
- Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Tokyo, Japan
| | - Shinji Maeda
- Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Tokyo, Japan
| | - Masahiko Makino
- Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yoshihiko Hoshino
- Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
- * E-mail: (TS); (YH)
| | - Makoto Kuroda
- Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan
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Ramos de Carvalho JE, Verbraak FD, Aalders MC, van Noorden CJ, Schlingemann RO. Recent advances in ophthalmic molecular imaging. Surv Ophthalmol 2013; 59:393-413. [PMID: 24529711 DOI: 10.1016/j.survophthal.2013.09.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 09/23/2013] [Accepted: 09/24/2013] [Indexed: 12/30/2022]
Abstract
The aim of molecular imaging techniques is the visualization of molecular processes and functional changes in living animals and human patients before morphological changes occur at the cellular and tissue level. Ophthalmic molecular imaging is still in its infancy and has mainly been used in small animals for pre-clinical research. The goal of most of these pre-clinical studies is their translation into ophthalmic molecular imaging techniques in clinical care. We discuss various molecular imaging techniques and their applications in ophthalmology.
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Affiliation(s)
- J Emanuel Ramos de Carvalho
- Ocular Angiogenesis Group, Departments of Ophthalmology and Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
| | - Frank D Verbraak
- Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Maurice C Aalders
- Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Cornelis J van Noorden
- Ocular Angiogenesis Group, Departments of Ophthalmology and Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Reinier O Schlingemann
- Ocular Angiogenesis Group, Departments of Ophthalmology and Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Netherlands Institute for Neuroscience, Royal Academy of Sciences, Amsterdam, The Netherlands.
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21
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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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22
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Capozzi ME, Gordon AY, Penn JS, Jayagopal A. Molecular imaging of retinal disease. J Ocul Pharmacol Ther 2013; 29:275-86. [PMID: 23421501 DOI: 10.1089/jop.2012.0279] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Imaging of the eye plays an important role in ocular therapeutic discovery and evaluation in preclinical models and patients. Advances in ophthalmic imaging instrumentation have enabled visualization of the retina at an unprecedented resolution. These developments have contributed toward early detection of the disease, monitoring of disease progression, and assessment of the therapeutic response. These powerful technologies are being further harnessed for clinical applications by configuring instrumentation to detect disease biomarkers in the retina. These biomarkers can be detected either by measuring the intrinsic imaging contrast in tissue, or by the engineering of targeted injectable contrast agents for imaging of the retina at the cellular and molecular level. Such approaches have promise in providing a window on dynamic disease processes in the retina such as inflammation and apoptosis, enabling translation of biomarkers identified in preclinical and clinical studies into useful diagnostic targets. We discuss recently reported and emerging imaging strategies for visualizing diverse cell types and molecular mediators of the retina in vivo during health and disease, and the potential for clinical translation of these approaches.
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Affiliation(s)
- Megan E Capozzi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-8808, USA
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Jaime GRL, Kashani AH, Saati S, Martin G, Chader G, Humayun MS. Acute variations in retinal vascular oxygen content in a rabbit model of retinal venous occlusion. PLoS One 2012; 7:e50179. [PMID: 23185567 PMCID: PMC3502464 DOI: 10.1371/journal.pone.0050179] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 10/22/2012] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To study the variation in intravascular oxygen saturation (oximetry) during an acute retinal vein occlusion (RVO) using hyperspectral computed tomographic spectroscopy based oximetry measurements. METHODS Thirty rabbits were dilated and anesthetized for experiments. Baseline oximetry measurements were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a fundus camera. RVO were induced using argon green laser following an intravenous injection of Rose Bengal. RVO induction was confirmed by fluorescein angiography. Retinal oximetry measurements were repeated in arterial and venous branches one hour after RVO induction and up to 4 weeks afterwards. Comparison of retinal oximetry before and after vein occlusion was made using the Student T-test. RESULTS One hour after RVO induction, we observed statistically significant reductions in the intravascular oxygen saturation in temporal retinal arteries (85.1 ± 6.1% vs. 80.6 ± 6.6%; p<0.0001) and veins (71.4 ± 5.5% vs. 64.0 ± 4.7%; p<0.0001). This decrease was reversible in animals that spontaneously recannulated the vein occlusion. There were no statistically significant differences in oxygen saturation in the nasal control arteries and veins before and after temporal vein RVO induction. CONCLUSIONS We demonstrate, for the first time, acute changes in the intravascular oxygen content of retinal vessels 1 hour after RVO. These changes are reversible upon spontaneous recannulation of retinal vessels. This study demonstrates that hyperspectral computer tomographic spectroscopy based oximetry can detect physiological variations in intravascular retinal oxygen saturation. The study also provides the first qualitative and quantitative evidence of the variation in retinal vascular oxygen content directly attributable to an acute retinal vein occlusion.
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Affiliation(s)
- Gilberto Raul Lopez Jaime
- Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
| | - Amir H. Kashani
- Department of Ophthalmology, William Beaumont Hospital and Associated Retinal Consultants P.C., Royal Oak, Michigan, United States of America
| | - Saloomeh Saati
- Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
| | - Gabriel Martin
- Reichert Technologies, Buffalo, New York, United States of America
| | - Gerald Chader
- Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
| | - Mark S. Humayun
- Doheny Eye Institute, University of Southern California, Los Angeles California, United States of America
- Department of Ophthalmology, Keck School of Medicine, University of Southern California Los Angeles, Los Angeles, California, United States of America
- Departments of Neuroscience and Biomedical Engineering, University of Southern California Los Angeles, Los Angeles, California, United States of America
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Wanek J, Blair NP, Shahidi M. Outer retinal oxygen consumption of rat by phosphorescence lifetime imaging. Curr Eye Res 2011; 37:132-7. [PMID: 22070458 DOI: 10.3109/02713683.2011.629071] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Since the metabolic function of the retinal tissue is altered due to physiologic changes or disease, measurements of outer retinal oxygen consumption (Q(OR)) may be beneficial in assessment of retinal status. The purpose of this study was to report measurements of Q(OR) in rats using a phosphorescence lifetime imaging technique. METHODS Phosphorescence lifetime imaging was performed and retinal PO(2) maps were generated in 10 rats under a light-adapted condition. Depth-resolved retinal PO(2) profiles were derived from the PO(2) maps. From the profiles, the maximum outer retina PO(2) (P(max)O(2)) was obtained and Q(OR) was calculated using a one-dimensional oxygen diffusion model. Repeatability, inter-location variability, and inter-subject variability of P(max)O(2) and Q(OR) measurements were established. RESULTS Intraclass correlation coefficients of repeated measurements of P(max)O(2) and Q(OR) were 0.89 and 0.70, respectively (P < 0.001). Inter-location variability of P(max)O(2) and Q(OR) measurements at superior to inferior contiguous locations on the retina were on average 9 mmHg and 0.22 ml O(2)/100 g-tissue-min, respectively. Mean and standard deviation of P(max)O(2) and Q(OR) measurements averaged over all rats were 60 ± 16 mmHg and 0.73 ± 0.28 ml O(2)/100 g-tissue-min, respectively. Inter-subject variability of P(max)O(2) and Q(OR) measurements was on average 2.3 and 1.5 times inter-location variability, respectively. CONCLUSIONS Measurements of outer retinal oxygen consumption can be made by phosphorescence lifetime imaging and may be of potential value for detecting changes in retinal oxygen metabolic activity due to altered physiological and pathological conditions over multiple locations and time points.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
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