. >> reporter: in some kalss, back on earth, the eyes correct themselves.ot his. >> i'm eagle eye at long distant. i need close-up specs. >> reporter: it's only on male astronauts. it could be increased pressure. doctors don't know if the problem would worsen or lead to blindness on longer flights say to mars. over the next five years, nasa is spending $18 billion to develop a new big rocket. this o'ryan spacecraft sent astronauts on the mission. if it's not solved, human mars missions could be in trouble. the alternative, get them there faster. >> i'm hopeful in 20 years we'll have capabilities to get us there in a matter of weeks to a few months and a lot of these problems go away. these problems go away. >> doctors are intensely working the problem of space station crews undergoing orbit exams and using special glasses called special focus. but so far, there haven't been any eye opening breakthroughs. >> and nasa astronaut mike merit joins me now from houston. thanks for joining us. this is fascinating. it's one of those things where you might not predic