A significant number of astronauts spending extended time aboard the International Space Station (ISS) have reported changes to their vision, raising concerns for future deep-space missions. Reports indicate that 70 percent of astronauts who have spent between six to twelve months in microgravity have experienced noticeable shifts in eyesight. Symptoms linked to spaceflight-associated neuro-ocular syndrome (SANS) include swelling of the optic nerve, flattening at the back of the eye, and vision impairment. The phenomenon is attributed to fluid redistribution in microgravity, which increases pressure on ocular structures. While many astronauts recover upon returning to Earth, the long-term impact remains uncertain, making it a critical issue for extended missions beyond low Earth orbit.

Findings of the Study

According to a study, Microgravity, researchers led by Santiago Costantino at the Université de Montréal examined 13 astronauts who had spent five to six months on the ISS. Participants from the United States, Europe, Japan and Canada, with an average age of 48, were included in the research. Eye measurements were taken before and after spaceflight, focusing on ocular rigidity, intraocular pressure, and ocular pulse amplitude. The study identified a 33 percent decline in ocular rigidity, an 11 percent reduction in intraocular pressure, and a 25 percent drop in ocular pulse amplitude. Some astronauts also exhibited an increase in choroidal thickness beyond normal levels.

Concerns for Long-Duration Space Travel

SANS has been observed since the early 2000s, with similar symptoms reported by Russian cosmonauts aboard the Mir space station. NASA officially classified the condition in 2011. Bodily fluid shifts in microgravity are believed to be the primary cause, although the exact mechanisms remain under investigation. Countermeasures such as negative pressure devices, pharmaceutical treatments, and targeted nutrition plans are being explored to mitigate risks.

Potential Solutions and Future Research

According to reports, ongoing research aims to identify astronauts at higher risk of developing severe ocular issues. As reported by space.com, Costantino noted that changes in the mechanical properties of the eye could serve as biomarkers for SANS, potentially assisting in early detection and intervention. Space agencies continue to prioritise the development of strategies to protect astronaut vision for future deep-space missions, including those to Mars.