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      Evaluation of colour vision impairment during acute hypobaric hypoxia in aviation medicine: a randomized controlled trial

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          Abstract

          The digitization of aircraft cockpits places high demands on the colour vision of pilots. The present study investigates colour vision changes upon acute exposure to hypobaric hypoxia. The digital Waggoner Computerized Color Vision Test and the Waggoner D-15 were performed by 54 healthy volunteers in a decompression chamber. Respective altitude levels were sea level, 10,000 or 15,000 ft for exposure periods of 15 and 60 min, respectively. As for 60 min of exposure a significant decrease in colour perception was found between subjects at 15,000 ft as compared to the control group as well as between subjects at 15,000 ft as compared to subjects at 10,000 ft. No significant difference was found in the comparison within the 15,000 ft groups across time points pre-, peri-, and post-exposure. Thus, pilots appear to experience only minor colour vision impairment up to an exposure altitude of 15,000 ft over 60 min of exposure.

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          Most cited references49

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          Energy metabolism of the visual system.

          The visual system is one of the most energetically demanding systems in the brain. The currency of energy is ATP, which is generated most efficiently from oxidative metabolism in the mitochondria. ATP supports multiple neuronal functions. Foremost is repolarization of the membrane potential after depolarization. Neuronal activity, ATP generation, blood flow, oxygen consumption, glucose utilization, and mitochondrial oxidative metabolism are all interrelated. In the retina, phototransduction, neurotransmitter utilization, and protein/organelle transport are energy-dependent, yet repolarization-after-depolarization consumes the bulk of the energy. Repolarization in photoreceptor inner segments maintains the dark current. Repolarization by all neurons along the visual pathway following depolarizing excitatory glutamatergic neurotransmission preserves cellular integrity and permits reactivation. The higher metabolic activity in the magno- versus the parvo-cellular pathway, the ON- versus the OFF-pathway in some (and the reverse in other) species, and in specialized functional representations in the visual cortex all reflect a greater emphasis on the processing of specific visual attributes. Neuronal activity and energy metabolism are tightly coupled processes at the cellular and even at the molecular levels. Deficiencies in energy metabolism, such as in diabetes, mitochondrial DNA mutation, mitochondrial protein malfunction, and oxidative stress can lead to retinopathy, visual deficits, neuronal degeneration, and eventual blindness.
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            Blood-retinal barrier in hypoxic ischaemic conditions: basic concepts, clinical features and management.

            The blood-retinal barrier (BRB) plays an important role in the homeostatic regulation of the microenvironment in the retina. It consists of inner and outer components, the inner BRB (iBRB) being formed by the tight junctions between neighbouring retinal capillary endothelial cells and the outer barrier (oBRB) by tight junctions between retinal pigment epithelial cells. Astrocytes, Müller cells and pericytes contribute to the proper functioning of the iBRB. In many clinically important conditions including diabetic retinopathy, ischaemic central retinal vein occlusion, and some respiratory diseases, retinal hypoxia results in a breakdown of the iBRB. Disruption of the iBRB associated with increased vascular permeability, results in vasogenic oedema and tissue damage, with consequent adverse effects upon vision. Factors such as enhanced production of vascular endothelial growth factor (VEGF), NO, oxidative stress and inflammation underlie the increased permeability of the iBRB and inhibition of these factors is beneficial. Experimental studies in our laboratory have shown melatonin to be a protective agent for the iBRB in hypoxic conditions. Although oBRB breakdown can occur in conditions such as accelerated hypertension and the toxaemia of pregnancy, both of which are associated with choroidal ischaemia and in age-related macular degeneration (ARMD), and is a feature of exudative (serous) retinal detachment, our studies have shown that the oBRB remains intact in hypoxic/ischaemic conditions. Clinically, anti-VEGF therapy has been shown to improve vision in diabetic maculopathy and in neovascular ARMD. The visual benefit in both conditions appears to arise from the restoration of BRB integrity with a reduction of retinal oedema.
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              The cerebral effects of ascent to high altitudes.

              Cellular hypoxia is the common final pathway of brain injury that occurs not just after asphyxia, but also when cerebral perfusion is impaired directly (eg, embolic stroke) or indirectly (eg, raised intracranial pressure after head injury). We Review recent advances in the understanding of neurological clinical syndromes that occur on exposure to high altitudes, including high altitude headache (HAH), acute mountain sickness (AMS), and high altitude cerebral oedema (HACE), and the genetics, molecular mechanisms, and physiology that underpin them. We also present the vasogenic and cytotoxic bases for HACE and explore venous hypertension as a possible contributory factor. Although the factors that control susceptibility to HACE are poorly understood, the effects of exposure to altitude (and thus hypobaric hypoxia) might provide a reproducible model for the study of cerebral cellular hypoxia in healthy individuals. The effects of hypobaric hypoxia might also provide new insights into the understanding of hypoxia in the clinical setting.
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                Author and article information

                Contributors
                felix.liebold@medizin.uni-leipzig.de
                Journal
                J Physiol Sci
                J Physiol Sci
                The Journal of Physiological Sciences : JPS
                BioMed Central (London )
                1880-6546
                1880-6562
                4 February 2024
                4 February 2024
                2024
                : 74
                : 6
                Affiliations
                [1 ]GRID grid.411097.a, ISNI 0000 0000 8852 305X, Department of Anaesthesiology und Intensive Care Medicine, , University Hospital and Faculty of Medicine Cologne, ; Cologne, Germany
                [2 ]GRID grid.411097.a, ISNI 0000 0000 8852 305X, Department of Ophthalmology, , University Hospital and Faculty of Medicine Cologne, ; Cologne, Germany
                [3 ]GRID grid.411097.a, ISNI 0000 0000 8852 305X, Department of Otorhinolaryngology, , University Hospital and Faculty of Medicine Cologne, ; Cologne, Germany
                [4 ]Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Essen, University of Duisburg-Essen, ( https://ror.org/04mz5ra38) Duisburg, Germany
                [5 ]Institute for Medical Informatics, Biometry and Epidemiology (IMBE), Friedrich-Alexander University Erlangen-Nuremberg, ( https://ror.org/00f7hpc57) Erlangen, Germany
                [6 ]Department of Medical and Clinical Psychology, Tilburg University, ( https://ror.org/04b8v1s79) Tilburg, Netherlands
                [7 ]Department of Sleep and Human Factor, German Aerospace Centre, ( https://ror.org/04bwf3e34) Linder Höhe, 51147 Cologne, Germany
                [8 ]GRID grid.411339.d, ISNI 0000 0000 8517 9062, Department of Anaesthesiology und Intensive Care Medicine, , University Hospital and Faculty of Medicine Leipzig, ; Liebigstraße 20, 04103 Leipzig, Germany
                [9 ]GRID grid.5570.7, ISNI 0000 0004 0490 981X, Johannes Wesling Klinikum Minden, University Hospital, , Ruhr University Bochum, ; Bochum, Germany
                Author information
                http://orcid.org/0000-0003-4684-7357
                Article
                898
                10.1186/s12576-024-00898-4
                10840265
                38311742
                b7bf69a8-8c7a-4b59-8eff-90d1b476545e
                © The Author(s) 2024

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 16 September 2023
                : 18 January 2024
                Funding
                Funded by: Universitätsklinikum Leipzig (8929)
                Categories
                Original Paper
                Custom metadata
                © The Physiological Society of Japan 2024

                Anatomy & Physiology
                colour vision,pilot assessment,hypobaric hypoxia,aircraft,eye
                Anatomy & Physiology
                colour vision, pilot assessment, hypobaric hypoxia, aircraft, eye

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