NASA is investigating a concerning medical condition affecting astronauts returning from long-duration missions aboard the International Space Station.
The disorder, now termed Space-Associated Neuro-Ocular Syndrome (SANS), is characterised by optic disc swelling, flattened eyeballs, and reduced vision, forcing many crew members to rely on stronger reading glasses.
The phenomenon stems from prolonged exposure to microgravity, causing fluids to accumulate in the upper body and head. These “headward shifts” raise brain pressure and affect ocular health, according to research cited by NASA. The space agency is conducting trials like the Thigh Cuff experiment to see if leg compression can reverse these changes.
Between 2015 and 2020, NASA’s Fluid Shifts study revealed altered blood drainage from the brain during spaceflight. Complementary projects used MRI scans, retinal imaging, and high-resolution eye exams to diagnose and understand the issue.
Further research is exploring the role of genetic changes, B vitamin supplements, and the cabin’s carbon dioxide levels in mitigating SANS symptoms. Emerging solutions such as optic nerve diameter assessments and virtual reality-based diagnostics offer new hope.
With Mars and Moon missions on the horizon, addressing SANS isn’t just critical for space travellers—it could inform treatment strategies for patients with similar fluid-related ailments on Earth.
