BOSTON—When astronaut Michael Barratt spent 200 days on the International Space Station, he expected to experience some unpleasant physical changes. Without Earth's gravity pulling down on his body, he'd lose bone and muscle mass, his body would produce fewer red cells, and his heart would atrophy. As a doctor specializing in aerospace medicine, however, Barratt knew how to counteract those changes with diet and exercise. What he wasn't prepared for was the blurry vision. As he explained here yesterday at the annual meeting of AAAS (which publishes ScienceNOW), he was surprised when his eyesight significantly deteriorated after several weeks in space. When he consulted the medical records from earlier shuttle missions, he noticed that many other astronauts had reported a similar problem, but that no one had thought to look for a common cause. Thanks to Barratt's observations and a follow-up MRI experiment, scientists now believe the astronauts' vision loss is a consequence of living in microgravity. Without Earth's gravity pulling the body's fluids down, there's more pressure in the skull, which leads to swollen optic nerves, slightly flattened eyeballs, and—you guessed it—blurry vision. According to Barratt, it's still unclear why so-called "spaceflight ocular syndrome" seems to affect more men than women, and whether it could translate to permanent damage once the astronauts return to Earth.
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