Space missions may damage eyes


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(Reuters Health) - Astronauts experience bone and muscle loss in the weightlessness of space, and now the first study of returning space travelers' eyes suggests that prolonged amounts of time in orbit can take a significant toll on vision, although the long-term effects aren't clear.

The new study, of more than 300 astronauts in the U.S. space program, found that almost 50 percent of those who served on long missions -- six months or more -- reported experiencing new problems with their ability to see objects near to them while in space and for some time after returning to Earth. Roughly 23 percent of astronauts who spent shorter periods in orbit reported problems with their near vision during their missions and after getting home.

The NASA-funded researchers also did physical exams on seven male astronauts who complained of vision problems after returning from six-month tours in space. They found several signs of eye stress in all of them, including a buildup of fluid around the optic nerve, the development of folds in the bed of vessels that supply blood to the retina, flattening of the eyeball and more.

"People have been flying in space for 50 years and nobody has gone blind yet," said Dr. Tom Mader, an ophthalmologist at the Alaska Native Medical Center, in Anchorage, who led the study. "But it's still something to be concerned about," he told Reuters Health.

Mader said the effects may be due to increased pressure of the fluid surrounding the brain -- the result of less gravity than on Earth -- that fails to drain well back into the body. But the precise mechanism is unclear.

It's possible that the loss of gravity causes pressure around the optic nerve to spike, which can damage vision, Mader said. It's also possible, however, that microgravity environments cause vision problems by lowering pressure in the eye, he added.

"It's very hard for us at this point to define exactly what is causing all of this," said Mader, whose group reported its findings in the journal Ophthalmology.

At least one of the seven astronauts examined in the study still displayed some of the documented physical eye changes more than five years after returning from space.

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Well apart from the risk of death just to even get there and back, and after all the possible diseases they can get, cancer from radiation, etc. all of the astronauts will tell you that it was wellworth it!

There would be lines longer than an Apple store on release night of people willing to sacrifice themselves and their body parts for the chance to go to space.

But good to know of the risks though. If we eventually send humans out on a long haul flight though the solar system and beyond, they might be blind by the time they reach their destination.

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