Astronauts are our heroes not only for the incredible work they do in space, but for the dramatic sacrifices they make to get there, leaving their loved ones and risking their lives. Then there are the small, but more common, dangers, like saying goodbye to their excellent eyesight. Researchers say that four out of every five astronauts on long-term missions return to Earth with a condition called visual impairment intracranial pressure syndrome (VIIP). 

Our bodies evolved in response to conditions on Earth. We are built to thrive in environments with a certain amount of gravity, a certain level of air pressure, and a certain concentration of oxygen in the air. We are not built for drifting through a vacuum in a highly pressurized metal box, even if that box was designed to feel like home. As a result, our space travelers return to Earth changed

One of the most prevalent changes is VIIP, which causes flattening of the backs of the eyeballs, pressure on the retinas, and inflammation of the optic nerve, which all lead to significant vision trouble. Astronaut John Phillips returned to the planet in 2005 to learn that his eyesight had gone from 20/20 to 20/100 in just six months. After another six months on the ground, his eyesight had improved to 20/50, where it has stayed ever since. 

You would think, given its name, that the root cause of VIIP would be clear: pressure inside the head. That’s the number one theory, and it may well be the cause. It also might not be. We don’t know for sure, because the best current methods for measuring intracranial pressure are drilling into someone’s skull or giving them a spinal tap—grisly procedures that most researchers deem far too dangerous to perform in space. 

J.D. Polk is a senior flight scientist at NASA. "There’s the risk for infection and just doing the procedure, quite frankly, in space is difficult,” Polk told the Washington Post. “Having to anchor somebody and do a spinal tap in space is not something we would relish.”

The clock is ticking on this one. NASA hopes to send astronauts to Mars in the next three decades. Before they do that, they need to know that the travelers won’t be incapacitated by the trip there.

So engineers and scientists are racing to find noninvasive methods for mid-flight measuring of internal skull pressure. In the meantime, space agencies continue to monitor every single bodily metric they can think of, from the vision test shown above to chemical analysis of urine samples.

Richard Williams, chief health and medical officer at NASA, says the bravery and selflessness of today’s astronauts are sure to benefit the space travelers of tomorrow: “The longer we stay in space, the more we’re going to learn.”

[h/t The Washington Post]

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