All astronauts have perfect eyesight before traveling to outer space, but some years ago medical tests revealed that their vision is severely impaired when they return. The exact cause of this problem is yet to be determined.
In 2005, about halfway through his mission working on the International Space Station, astronaut John Phillips looked out the window at Earth and noticed something strange. Although his vision had always been perfect, our planet seemed blurry and he had problem focusing on it. He didn’t report his problem to ground control thinking it was just temporary and would go away after a while, only it didn’t. When he returned to Earth, rigorous tests revealed that his eyesight had gone from 20/20 to 20/100.
To shed some light on this issue, NASA put Phillips through a series of procedures, including MRIs, retinal scans, neurological tests and a spinal tap. They found that not only had his vision deteriorated, but his eyes had changed as well – his optic nerves were inflamed, the back of his eyes had become flatter and his eyeballs had choroidal folds, which are like stretch marks. After six months, Phillips’ eyesight improved to 20/50, but remained there for the last 11 years. He went from being the guy with the best vision, the first one in the car to read a street sign to not being able to pass a DMV exam without glasses.