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Prolonged microgravity exposure during long-duration spaceflight (LDSF) produces interesting, unique, and unusual physiologic and pathologic neuro-ocular findings in astronauts. These microgravity associated findings collectively define the "Spaceflight Associated Neuro-ocular Syndrome" (SANS) and SANS is a disorder with no terrestrial equivalent. The United States’ National Aeronautics and Space Administration's (NASA) Space Medicine Operations Division in conjunction with space agencies and other space medicine researchers and organizations worldwide have conducted retrospective and prospective studies on SANS to better understand and potentially treat the disorder. The clinical manifestations of SANS include: unilateral and bilateral optic disc oedema, globe flattening, choroidal and retinal folds, hyperopic refractive error shifts, and focal areas of ischemic retina (i.e., cotton wool spots). Continued future research on SANS is necessary in preparation for future longer duration crewed space missions to the moon and to Mars.