Science Of...

Why Does Space Impair Your Vision?

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Humans have been going into space for 50 years, but scientists are still discovering new things about what microgravity does to the human body. For example, astronauts have been reporting worsening vision since the first crewed space flights, but it wasn't until flights stretched to weeks and months at a time that the extent of this problem came to light.

Now You See Me

In post-flight examinations on 300 astronauts since 1989, 29% of astronauts experienced worse vision after a two-week mission in the space shuttle and 60% experienced it after a five- to six-month tour of duty in the International Space Station. Most of the time, astronauts notice more far-sightedness, usually from a strange "flattening" of the eyeball and swelling of the optic nerve.

What's The Cause?

Scientists aren't entirely sure what's causing the vision problems, but they have a few guesses. Some think it could be elevated intracranial pressure, that is, pressure in the brain and spinal fluid, since people with this issue have similar vision problems. Other hypotheses involve the elevated carbon dioxide levels in the air astronauts breathe, the large amount of sodium in their diets, or radiation exposure. To help figure out the cause, astronauts use advanced medical equipment to perform eye exams on each other in space while physicians examine the results from Earth.

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Chris Hadfield explains the strange things that happen to an astronaut's eyes.

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There are no ophthalmologists in space, so astronauts are left to their own devices.

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