How Does NASA Study Vision and Cognitive Changes in Space? – Thursday, June 11, 2026

Did you know 70% of astronauts experience swelling in the back of their eyes during spaceflight? This is known as SANS, or Spaceflight Associated Neuro-ocular Syndrome. Scientists believe it results from upward fluid shifts in weightlessness. But a key question remains: Do these changes fully resolve after flight or do they persist? To find out, a new study from NASA’s Human Research Program is looking at the long-term effects of flight-induced eye and brain changes in astronauts up to five years after their mission. Both active and retired crews will go through a series of exams that assess visual fields, eye pressure, cognitive function, and more. By keeping an eye on the vision and brain health of spacefarers, NASA will be better equipped with the protocols needed to ensure humans are healthy on missions to the Moon, Mars, and beyond. Join NASA as we go forward to the Moon and on to Mars -- discover the latest on Earth, the Solar System and beyond with a weekly update in your inbox. Subscribe at: https://www.nasa.gov/subscribe

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Did you know that 70% of astronauts aboard the International Space Station experience swelling in the back of their eyes? This condition is called Spaceflight Associated Neuro-ocular Syndrome, or SANS. Scientists think it may result from shifts of blood, spinal, and other fluids while astronauts are in weightlessness. Without gravity to pull fluids downward, fluids can build around the eyes and brain. When astronauts come home, the swelling lessens and vision improves.

But a key question remains: Do these changes fully resolve after flight, or do they persist even subtly? To find out, NASA is studying how spaceflight affects long-term eye and brain health up to five years after flight. Researchers plan to recruit 20 astronauts, either retired or active crew members Who have traveled on long-duration missions aboard the space station. They'll also recruit 20 Earth volunteers, matched for age and body type to distinguish normal aging from spaceflight-related changes. To assess eye health, participants undergo thorough eye exams, which measure the extent of their visual fields and check eye pressure.

Astronauts also view different flashing lights and image patterns while a sensor at the eye base records their eye responses. Brain health is evaluated through MRI scans, neurological and cognitive tests, a blood draw, and surveys. By assessing the long-term eye and brain health of space travelers, NASA keeps its sights on sending humans to the Moon, Mars and beyond.

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