Vision problems plaguing some astronauts

Going to outer space is no walk in the park. There are a lot of things to worry about when leaving the comfort and safety of planet earth. And now we can add another one to the list. It's called visual impairment intracranial pressure syndrome, or VIIP for short. It's ruining astronauts' eyesight, and NASA is not entirely sure why.

Dr. Rich Williams is NASA's chief health and medical officer. He said the space agency began noticing the problem when astronauts started flying longer-term missions in space. In one case in 2005, Astronaut John Phillips's eyesight had gone from 20/20 to 20/100 after six months on the International Space Station.

"What we don't know is what happens to this the longer people stay in space," Williams says. "That's an unanswered question. There are many unanswered questions about this up to and including what actually causes it."

The reason it is called VIIP is because of the leading theory as to why this happens. In a nutshell, bodily fluid normally pulled toward our feet by gravity on earth builds up in the skull during spaceflight. This leads to physical changes in parts of the eye and, in turn, causes some astronauts to lose their visual acuity, making them farsighted.

"Losing a line or two on the eye chart compared to what else can happen to you there -- that's not a bad deal," says former NASA Astronaut Mike Massimino. He says VIIP has the potential to cause headaches for NASA missions.

"During the mission if your eyeball starts changing, that might affect the mission," he says. "If you're going go on a long journey to Mars and you have to land a spaceship on Mars or land a spaceship back here, you have to see what's in front of you. So you need very good eyesight in order to perform your job up there."

One of the big unanswered questions for NASA is whether or not the condition grow worse the longer someone is in space or does it simply plateau and therefore could be fixed with glasses.

"It's probably at the top of the list of medical concerns in terms of low earth orbit and needing to understand it -- and they will. They'll get to the bottom of it," Massimino says. "You need to use the space station to understand all these problems that you might encounter. So this is one that we've discovered. And it's good to discover it now when you can manage it and try to solve it before you send people further away from the planet."

NASA is quick to point out that this is by no means a "Houston, we have a problem" type issue. But it does raise some serious concerns for future human spaceflight.

Right now, NASA's plan is to get humans to an asteroid by 2025 and then on to Mars in the 2030s. They should have this one figured out by then.