State of the Retina and Optic Nerve in 21-Day Head-Down Tilt Bed Rest

Abstract: Studies in conditions of head-down tilt bed rest (HDTBR) are widely used experiments that imitate redistribution of body fluids similar to the redistribution of fluid media in microgravity. To study the mechanism of development of spaceflight-associated neuro-ocular syndrome (SANS) in HDTBR, scientists have evaluated, among other things, visual system parameters in participants. The main symptom of SANS is a developing edema of the optic disc and retina. To date, the results describing the influence of HDTBR on the visual system are ambiguous, which determines the relevance of further research. The aim of the study was to analyze retinal morphometry in the optic disc area and macular area in test participants before and after 21-day HDTBR. The study was performed using an optical coherence tomography with angiography function (Optovue RTVue XR Avanti System) before and after 21-days of HDTBR. In four participants (eight eyes) (men, mean age ± standard deviation: 29.3 ± 3.9 years) the macular zone and optic disc area were evaluated according to standard scanning modes. To analyze the values, we used mean tendency scores, mean comparison criteria, and graphical analysis. The results of the retinal thickness in the optic disc zone were consistent with those of other researchers, indicating a possible increase in retinal thickness, but our results did not reach the level of statistical significance. A statistically significant thickening of the retina in the macular zone was shown for the first time, but the increase is significantly less in amplitude than the thickening of the nerve fiber layer in the optic disc zone. Analysis of vascular density under HDTBR conditions was performed for the first time both for the optic disc zone and the macula zone. Additional studies are required to obtain steady conclusions. For the first time, an increase in retinal thickness in the macula zone in participants of HDTBR experiments was shown; for the optic disc zone, data consistent with the results of other researchers were obtained. For the first time, angiographic data were obtained for the macula and optic disk areas, but the obtained differences in vascular density did not reach the level of statistical significance. © 2023, Pleiades Publishing, Inc.