Analysis of the anatomical and functional ocular changes related to spaceflight

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Purpose: To describe novel early changes in ocular physiology following short-duration exposure to microgravity. Observations: The subject was a 64-year-old astronaut who participated in the AX-1 mission that was sent to the International Space Station by AXIOM Space and the National Aeronautics and Space Administration (NASA) in April 2022 for 17 days. Comprehensive multimodal preflight and postflight ophthalmic examinations were performed, including anterior and posterior segment imaging and head magnetic resonance imaging (MRI). In addition, optical coherence tomography angiography (OCTA), which is not part of the standard NASA protocol, was conducted for the first time in this setting in the medical literature. Automated image processing was used to quantify flow signal pixels from the retina or choroid for separate analysis. The subject reported a new-onset need for reading glasses while in space. Mild widening of the optic nerve sheaths was found on MRI. OCTA studies demonstrated a significant postflight decrease in macular choroidal flow signals by 29% in the right eye and 11% in the left eye, and in retinal flow signals by 8.5% and 6.5%, respectively (p < 0.0001 for both factors for both eyes). Focal alterations were noted in choroidal thickness and Haller’s vessel diameter, which did not reach statistical significance. Conclusion: A significant decrease in macular choroidal and retinal blood flow was observed in an astronaut after a short-duration spaceflight. These changes may serve as possible biomarkers of spaceflight-associated neuro-ocular syndrome and warrant further investigation. We recommend that future spaceflight evaluations include OCTA in the standard protocol.

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