Space missions have been growing not just in number but also in the time spent in space. Because of this, astronauts started to notice something that troubled them. They found that their time in space may be causing their eyesight to worsen.

A report by Popular Mechanics found that John Phillips, an astronaut who has spent over six months on the International Space Station in 2005, claimed he started to have problems with his eyesight while he was in space. However he was hesitant to report it.

"I'm not sure if I reported that to the ground," he said. "I think I didn't. I thought it would be something that would just go away, and fix itself when I got to Earth," Phillips said.

During the routine post-flight medical exam, doctors discovered that Phillips' once 20/20 eyesight had deteriorated to 20/100. Another surprising thing is that, Phillips was not the only one who experienced deteriorated eyesight.

This is an extremely serious issue that needs to be addressed before humans can realistically expect to expand into the solar system.  To read more, click here.