Astronaut John Phillips spent more than six months on the International Space Station. When he returned to Earth, he found his eyesight had gone from 20/20 to 20/100, Popular Mechanics reports.
Phillips wasn't alone. It seems that 80 percent of astronauts suffer from visual impairment intracranial pressure syndrome (VIIP). The name only describes one theory about how the damage happens, though. Scientists have yet to figure it out.
After Phillips landed, he was subjected to MRIs and retinal scans, which revealed that while in space, the backs of his eyes were flattened and his retinas pushed forward. His optic nerve was also inflamed and his eyes showed choroidal folds -- essentially stretch marks.
Read the full story: