Abstract
The study of eye hydrodynamics following five-day “dry” immersion (DI) was aimed at evaluating the influence of compensatory body hypohydration on the intraocular hydrodynamic balance. For the first time the data of electronic eye tonography before and after modeled microgravity were compared. The study involved ten male volunteers 24 to 40 years of age without ophthalmologic pathologies. Electronic eye tonography results and hypohydration dynamics were assessed by fluid balance. Electronic tonography was performed before DI and on post-DI days 1 and 7 to measure the true intraocular pressure and to calculate the intraocular fluid production rate (F), coefficient of aqueous humor outflow ease, Bekker coefficient, and trophic coefficient (TC). On post-DI day 1, F reduction was observed in eight volunteers (60% of cases, 12 eyes). Level of the F reduction varied from 40% of the baseline value (5 eyes) to abnormally low 54% (7 eyes) underlying trophic changes. TC went down in 60% of cases (12 eyes); in 50% of cases (6 eyes) TC reduction was clinically significant. By the seventh day after DI, intraocular hydrodynamics was comparable with the baseline. It is hypothesized that the reflectory hypohydration during DI (the Gauer–Henry reflex) is responsible for changes in the intraocular hydrodynamics; the depth of these changes is determined by the degree of compensatory hypothalamic influence upon the antidiuretic hormone-angiotensin II system.
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Funding
The study was conducted as a part of the basic subjects of the Russian Academy of Sciences no. 63.1 “Investigation of the Mechanisms of Sensory and Motor Functioning in Conditions of Altered Gravity and Conceptualization of the Prevention of Microgravity Disturbances in Extralong Space Missions” and no. 63.2 “Investigation of Integrative Processes in the Central Nervous System, Regularities of Human Behavior and Activity in the Noninteracting Conditions and under Extreme Environmental Factors”, and supported by the Russian Foundation of Basic Research, project no. 16-29-083120-OFI-m “Determination of the Optimal Characteristics of Proprioceptive Signals of Various Modality (Supporting, Muscular, and Vestibular) Aimed to Elaborate the Algorithms of their Application in the System of Multimodal Soft Exosceleton with Neurorehabilitative and Space Flight Purposes.”
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Statement of compliance with standards of research involving humans as subjects. The experimental procedure involving humans was approved by the Biomedical Ethics Committee of the Institute of Biomedical Problems of the Russian Academy of Sciences in the level of scientific evidence, sufficiency of medical control, and safety arrangements (protocol no. 471, March 15, 2018). The risk and discomfort experienced during the experiment was accepted as tolerable. Informed consent was obtained from all individual participants involved in the study.
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Translated by E. Sherstyuk
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Man’ko, O.M., Smoleevskii, A.E., Tomilovskaya, E.S. et al. Effect of Five-day “Dry” Immersion on Eye Hydrodynamics. Hum Physiol 46, 792–797 (2020). https://doi.org/10.1134/S0362119720070105
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DOI: https://doi.org/10.1134/S0362119720070105