NASA studies astronauts' vision decrease problem

NASA has launched a study on why the astronauts' vision decrease after long-term space missions, according to media reports Tuesday.

NASA said 30 percent of about 300 astronauts, who have working time in space ranging form 2 weeks to 6 months, have reported a gradual blurring of eyesight.

Doctors believe the disorder was caused by increased spinal fluid pressure on the head and eyes due to microgravity in space.

NASA worried that future explorers could go blind by the end of long missions, such a multi-year trip to Mars.

"We are certainly treating this with a great deal of respect," said Rich Williams, NASA's chief health and medical officer.

The special eyeglasses have been put on to help those affected astronauts on the space station, according to NASA.

But to reveal the exact mechanism of the disorder still needs further study, NASA said.