Astronauts who have spent extended periods aboard the International Space Station (ISS) have reported significant changes to their vision, prompting concerns about the effects of long-duration space travel on eyesight. Research indicates that 70 percent of astronauts who spent six to twelve months in microgravity have experienced shifts in their vision. This phenomenon is linked to spaceflight-associated neuro-ocular syndrome (SANS), a condition that involves swelling of the optic nerve, flattening at the back of the eye, and various degrees of vision impairment. It is believed that fluid redistribution in microgravity increases pressure on ocular structures, contributing to these changes. While many astronauts recover their vision after returning to Earth, the long-term effects of SANS are still unclear, making it a critical concern for missions beyond low Earth orbit, such as those planned for Mars.
A study led by Santiago Costantino at the Université de Montréal has provided new insights into how prolonged exposure to microgravity affects astronauts’ eyes. The research involved 13 astronauts, with participants from the United States, Europe, Japan, and Canada, who spent between five to six months aboard the ISS. Before and after their space missions, measurements were taken to assess ocular rigidity, intraocular pressure, and ocular pulse amplitude. The study found that ocular rigidity decreased by 33 percent, intraocular pressure dropped by 11 percent, and ocular pulse amplitude was reduced by 25 percent. Additionally, some astronauts experienced an increase in choroidal thickness, which could contribute to vision problems. These findings underline the serious implications of space travel on astronaut health.
SANS has been a known issue since the early 2000s, with Russian cosmonauts aboard the Mir space station reporting similar vision-related symptoms. NASA formally recognized the condition in 2011. While fluid shifts in microgravity are believed to be the primary cause of SANS, researchers are still working to fully understand the mechanisms at play. The condition poses a significant challenge for future deep-space missions, where astronauts will face extended periods away from Earth, potentially exacerbating the effects on their vision. As the duration of space missions increases, it becomes increasingly important to address this issue to ensure the health and safety of astronauts.
To mitigate the risks associated with SANS, researchers are exploring various countermeasures. These include negative pressure devices that may help regulate fluid distribution in the body, pharmaceutical treatments that target ocular pressure, and specialized nutrition plans to support eye health during space travel. However, until more is known about the long-term impacts of spaceflight on vision, further studies will be essential to developing effective solutions for future missions, especially those aiming for Mars, where astronauts may experience extended exposure to microgravity and its effects on their bodies.