Automated MRI-based quantification of posterior ocular globe flattening and recovery after long-duration spaceflight

• Type of Material: Article
• Authors: Christopher Ethier, Emory University; Stuart H Sater, Alcyone Therapeutics Inc.; Austin M Sass, University of Idaho; Jesse J Rohr, University of Idaho; Karina Marshall-Goebel, KBR, Houston; Robert J Ploutz-Snyder, University of Michigan; Michael B Stenger, National Aeronautics and Space Administration; Larry A Kramer, University of Texas Health Science Center at Houston; Bryn A Martin, Alcyone Therapeutics Inc.; Brandon R Macias, National Aeronautics and Space Administration
• Language: English
• Date: 2021-01-29
• Publisher: SPRINGERNATURE
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2021
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1038/s41433-021-01408-1
• Title of Journal or Parent Work: EYE
• Volume: 35
• Issue: 7
• Start Page: 1869
• End Page: 1878
• Grant/Funding Information: This study was funded by NASA grants 80NSSC20K0920, NNX16AT06G and 80NSSC19K1298; NASA Idaho Space Grant Consortium grant #NNX10AM75H; National Institute of Neurological Disorders and Stroke grant #tatistics; the Georgia Research Alliance; and the NASA Human Research Program.
• Keywords: Life Sciences & Biomedicine; Science & Technology; Ophthalmology; INTRACRANIAL HYPERTENSION; OPTIC DISC EDEMA
• Research Categories: Engineering, Biomedical; Biology, Biostatistics

Abstract

Background/Objectives: Spaceflight associated neuro-ocular syndrome (SANS), a health risk related to long-duration spaceflight, is hypothesized to result from a headward fluid shift that occurs with the loss of hydrostatic pressure gradients in weightlessness. Shifts in the vascular and cerebrospinal fluid compartments alter the mechanical forces at the posterior eye and lead to flattening of the posterior ocular globe. The goal of the present study was to develop a method to quantify globe flattening observed by magnetic resonance imaging after spaceflight. Subjects/Methods: Volumetric displacement of the posterior globe was quantified in 10 astronauts at 5 time points after spaceflight missions of ~6 months. Results: Mean globe volumetric displacement was 9.88 mm3 (95% CI 4.56–15.19 mm3, p < 0.001) on the first day of assessment after the mission (R[return]+ 1 day); 9.00 mm3 (95% CI 3.73–14.27 mm3, p = 0.001) at R + 30 days; 6.53 mm3 (95% CI 1.24–11.83 mm3, p < 0.05) at R + 90 days; 4.45 mm3 (95% CI −0.96 to 9.86 mm3, p = 0.12) at R + 180 days; and 7.21 mm3 (95% CI 1.82–12.60 mm3, p < 0.01) at R + 360 days. Conclusions: There was a consistent inward displacement of the globe at the optic nerve, which had only partially resolved 1 year after landing. More pronounced globe flattening has been observed in previous studies of astronauts; however, those observations lacked quantitative measures and were subjective in nature. The novel automated method described here allows for detailed quantification of structural changes in the posterior globe that may lead to an improved understanding of SANS.