Spaceflight-Associated Neuro-Ocular Syndrome

Article: Living in outer space: Changes in blood flow volume may be at the heart of worsening eyesight
Source: Medical University of South Carolina
Published: January 6, 2022

Colonizing a planet beyond Earth may still be in the realm of science fiction for now; however, scientists are already studying the effects of spaceflight and living in other gravity conditions to prepare for that future, before they affect colonists on a foreign planet. Well-reported effects of outer space include bone loss, cosmic radiation, and muscle weakness. Less studied are the effects on the brain and gravity's effects on the eyes, in particular spaceflight-associated neuro-ocular syndrome (SANS). Neurology resident and first author of the paper explains that the longer astronauts stay in space, the more they’ve reported blurry vision and eyesight problems when they return to Earth. He states, "It's gotten to the point where astronauts actually carry extra pairs of glasses when they go into space...And, in fact, depending on how you define it, it affects about 70% of astronauts.” Signs of SANS include a flatten globe (consistent with a hyperopic shift in refractive error), areas of retinal injury, and optic disc swelling. Among their study cohort of 12 astronauts, the researchers found that 4 astronauts who met the diagnostic criteria for SANS had significantly greater preflight to postflight increases in intracranial dural venous volumes (in the superior sagittal sinus and both right and left transverse/sigmoid sinuses, as measured by magnetic resonance venography) than astronauts without SANS, suggesting an association between intracranial venous congestion and the development of SANS. Recovery can take weeks, months, or even years, and some astronauts never fully recover. Studying how gravity affects the brain in outer space also informs doctors about how gravity affects neurological states, such as disorders of cerebrospinal fluid circulation, here on earth. The researchers next plan to study a larger cohort of astronauts, gender differences in SANS, and to better pinpoint when the changes leading to SANS begin to develop.

Preflight and postflight venograms for an astronaut with SANS (left) and an astronaut without SANS (right)

My rating of this study: ⭐⭐

Rosenberg MJ, Coker MA, Taylor JA, et al. "Comparison of Dural Venous Sinus Volumes Before and After Flight in Astronauts With and Without Spaceflight-Associated Neuro-Ocular Syndrome." JAMA Network Open.  4(10):e2131465. 27 October 2021. https://doi.org/10.1001/jamanetworkopen.2021.31465

See also: Lower Body Negative Pressure Can Lessen Spaceflight-Associated Neuro-Ocular Syndrome