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Diabetic macular ischaemia- a new therapeutic target? Prog Retin Eye Res 2021; 89:101033. [PMID: 34902545 DOI: 10.1016/j.preteyeres.2021.101033] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 11/25/2021] [Accepted: 12/01/2021] [Indexed: 12/21/2022]
Abstract
Diabetic macular ischaemia (DMI) is traditionally defined and graded based on the angiographic evidence of an enlarged and irregular foveal avascular zone. However, these anatomical changes are not surrogate markers for visual impairment. We postulate that there are vascular phenotypes of DMI based on the relative perfusion deficits of various retinal capillary plexuses and choriocapillaris. This review highlights several mechanistic pathways, including the role of hypoxia and the complex relation between neurons, glia, and microvasculature. The current animal models are reviewed, with shortcomings noted. Therefore, utilising the advancing technology of optical coherence tomography angiography (OCTA) to identify the reversible DMI phenotypes may be the key to successful therapeutic interventions for DMI. However, there is a need to standardise the nomenclature of OCTA perfusion status. Visual acuity is not an ideal endpoint for DMI clinical trials. New trial endpoints that represent disease progression need to be developed before irreversible vision loss in patients with DMI. Natural history studies are required to determine the course of each vascular and neuronal parameter to define the DMI phenotypes. These DMI phenotypes may also partly explain the development and recurrence of diabetic macular oedema. It is also currently unclear where and how DMI fits into the diabetic retinopathy severity scales, further highlighting the need to better define the progression of diabetic retinopathy and DMI based on both multimodal imaging and visual function. Finally, we discuss a complete set of proposed therapeutic pathways for DMI, including cell-based therapies that may provide restorative potential.
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Schwab C, Paar M, Fengler VH, Ivastinovic D, Haas A, Seidel G, Glatz W, Malle EM, Weger M, Velikay-Parel M, Faustmann G, Wedrich A, Reibnegger G, Winklhofer-Roob B, Oettl K. Gender differences in albumin and ascorbic acid in the vitreous antioxidant system. Free Radic Biol Med 2020; 146:257-263. [PMID: 31705958 DOI: 10.1016/j.freeradbiomed.2019.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 10/24/2019] [Accepted: 11/04/2019] [Indexed: 11/21/2022]
Abstract
Ascorbic acid is present at high concentrations in the vitreous and plays a central role in vitreous redox chemistry. Albumin is the main protein in the vitreous with antioxidant properties and occurs in different oxidation states, which can be used as redox indicators, but have not been studied in the vitreous. This study, therefore, addressed the vitreous redox state of cysteine-34 of albumin in relation to the ascorbic acid content, which has been suggested to exert a main function in detoxifying reactive oxygen in the vitreous. A total of 58 vitreous samples obtained from patients undergoing vitrectomy were analyzed for (i) human mercaptalbumin (HMA), the reduced thiol form; (ii) human non-mercaptalbumin1 (HNA1), a reversible oxidative modification with a disulfide at cysteine-34; and (iii) human non-mercaptalbumin2 (HNA2), a non-reversibly (highly) oxidized form of albumin; as well as (iv) ascorbic acid concentrations, to study possible relations. In addition, blood samples were taken to compare albumin redox state between plasma and the vitreous. Vitreous albumin showed greater variability in the redox state of cysteine-34 and a shift to the oxidized fractions compared to plasma albumin (P < 0.001). A strong positive relation was observed between the vitreous ascorbic acid concentrations and the reversibly oxidized form, HNA1 (P < 0.001), and a negative relation with the reduced form, HMA. Positive relations between ascorbic acid and HNA1 in the vitreous were stronger in men than in women. In contrast to HMA and HNA1, there was a distinct gender difference noted for the irreversibly oxidized form, HNA2. While males showed a positive relation between the vitreous ascorbic acid concentrations and HNA2, there was no correlation found with HNA2 in females. Our results support the view that ascorbic acid, by decreasing either directly or indirectly the concentrations of molecular oxygen, generates hydrogen peroxide, and that thiols, including HMA, are acting as antioxidants. This study for the first time provides evidence that vitreous albumin can be used as a marker molecule for the appearance of reactive oxygen species in the vitreous of patients undergoing vitrectomy. Moreover, it can be shown that there are gender differences in vitreous ascorbic acid and albumin concentrations as well as in oxidation state of vitreous albumin.
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Affiliation(s)
- Christoph Schwab
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Margret Paar
- Physiological Chemistry, Otto-Loewi Research Center, Medical University of Graz, Neue Stiftingtalstraße 6, 8010 Graz, Austria.
| | - Vera Heike Fengler
- Physiological Chemistry, Otto-Loewi Research Center, Medical University of Graz, Neue Stiftingtalstraße 6, 8010 Graz, Austria
| | - Domagoj Ivastinovic
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Anton Haas
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Gerald Seidel
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Wilfried Glatz
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Eva-Maria Malle
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Martin Weger
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Michaela Velikay-Parel
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Gernot Faustmann
- Human Nutrition & Metabolism Research and Training Center, Institute of Molecular Biosciences, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Andreas Wedrich
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036 Graz, Austria
| | - Gilbert Reibnegger
- Physiological Chemistry, Otto-Loewi Research Center, Medical University of Graz, Neue Stiftingtalstraße 6, 8010 Graz, Austria
| | - Brigitte Winklhofer-Roob
- Human Nutrition & Metabolism Research and Training Center, Institute of Molecular Biosciences, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Karl Oettl
- Physiological Chemistry, Otto-Loewi Research Center, Medical University of Graz, Neue Stiftingtalstraße 6, 8010 Graz, Austria
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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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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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Šín M, Chrapek O, Karhanová M, Šínová I, Špačková K, Langová K, Řehák J. The effect of pars plana vitrectomy and nuclear cataract on oxygen saturation in retinal vessels, diabetic and non-diabetic patients compared. Acta Ophthalmol 2016; 94:41-7. [PMID: 26310901 DOI: 10.1111/aos.12828] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 07/12/2015] [Indexed: 12/13/2022]
Abstract
PURPOSE To determine the effect of pars plana vitrectomy (PPV) on oxygen saturation in retinal vessels in patients with diabetes and non-diabetes after a 1-year follow-up. METHODS This was a prospective consecutive interventional case series in 82 eyes in 82 patients. The sample consisted of 25 patients with non-proliferative diabetic retinopathy with macular oedema based on vitreoretinal traction or epiretinal membrane (ERM) and 57 non-diabetic patients with macular hole and ERM. Automatic retinal oximetry (Oxymap Inc.) was used on all patients 24 hr prior to PPV, and it was also used 7 and 52 weeks after PPV (classic 20G or sutureless 23G). We analysed the data according to subgroup diagnosis and lens status. RESULTS Arterial saturation increased significantly from 96.4 ± 2.9% at baseline to 96.6 ± 3.4% at week 7 and 97.3 ± 3.4% at week 52 (p < 0.0001; Friedman test). Vein saturation also increased significantly from 63.5 ± 7.9% at baseline to 66.1 ± 7.7% and 67.0 ± 7.2% at weeks 7 and 52 (p < 0.0001; Friedman test). The value of the arteriovenous (A-V) difference decreased significantly after vitrectomy from 32.8 ± 7.5% at baseline to 30.5 ± 7.5% and 30.3 ± 7.0% at weeks 7 and 52 (p < 0.0001; Friedman test). The subgroup analysis revealed that in patients with diabetes, there were no statistically significant changes in oxygen saturation in blood vessels or in the A-V difference after PPV. After vitrectomy, retinal vessel diameter reduced by about 3.5% in both groups of patients. Further, the analysis revealed that opacification of the lens leads to a decrease in oxygen saturation in contrast to a clear lens and pseudophakic IOLs. CONCLUSION Oxygen saturation is higher in the retinal veins and arteries after PPV in patients with non-diabetes, and this lasts for at least 52 weeks. In contrast, in patients with diabetes, there is no increase in oxygen saturation in the retinal vessels after vitrectomy. After vitrectomy, retinal vessel diameter reduced in both groups of patients. Further, the nuclear cataract progression has substantial effect on oximetry results. Patients with nuclear cataract exhibited an increase in saturation in both arteries and veins, but the A-V difference remained the same.
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Affiliation(s)
- Martin Šín
- Department of Ophthalmology; University Hospital and Faculty of Medicine and Dentistry; Palacky University; Olomouc Czech Republic
| | - Oldřich Chrapek
- Department of Ophthalmology; University Hospital and Faculty of Medicine and Dentistry; Palacky University; Olomouc Czech Republic
| | - Marta Karhanová
- Department of Ophthalmology; University Hospital and Faculty of Medicine and Dentistry; Palacky University; Olomouc Czech Republic
| | - Irena Šínová
- Department of Ophthalmology; University Hospital and Faculty of Medicine and Dentistry; Palacky University; Olomouc Czech Republic
| | | | - Kateřina Langová
- Department of Medical Biophysics; Faculty of Medicine and Dentistry; Institute of Molecular and Translational Medicine; Palacky University; Olomouc Czech Republic
| | - Jiří Řehák
- Department of Ophthalmology; University Hospital and Faculty of Medicine and Dentistry; Palacky University; Olomouc Czech Republic
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Sín M, Sínová I, Chrapek O, Prachařová Z, Karhanová M, Langová K, Rehák J. The effect of pars plan vitrectomy on oxygen saturation in retinal vessels--a pilot study. Acta Ophthalmol 2014; 92:328-31. [PMID: 23848230 DOI: 10.1111/aos.12238] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To determine the effect of pars plana vitrectomy (PPV) on oxygen saturation in retinal vessels. METHODS We performed a prospective consecutive interventional case series of 20 eyes of 20 patients with macular hole or epiretinal membrane. We performed automatic retinal oximetry (Oxymap Inc., Reykjavik, Iceland) in each patient 24 hr prior to and 45 days (range 42-49) after PPV (classic 20G or sutureless 23G). We analysed oxygen saturations in retinal arteries and veins. Vessel segments of first or second degree were selected. The same segment was analysed before and after PPV. Oximetry data were compared by paired two-tailed t-test. RESULTS Pars plana vitrectomy did not alter arterial haemoglobin saturation with oxygen (98±2% prior to the surgery and 98±3% after the procedure, p=0.549). The mean venous haemoglobin saturation with oxygen increased after vitrectomy from 63±10% to 66±8% (p=0.012). CONCLUSIONS Oxygen saturation is higher in retinal veins after pars plana vitrectomy. Further studies are needed to unveil the mechanism of how vitrectomy affects oxygen metabolism in the retina.
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Affiliation(s)
- Martin Sín
- Department of Ophthalmology, Faculty of Medicine and Dentistry, University Hospital, Palacky University Olomouc, Olomouc, Czech RepublicDepartment of Medical Biophysics, Faculty of Medicine and Dentistry, Institute of Molecular and Translational Medicine, Palacky University, Olomouc, Czech Republic
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