Space flight may be bad for your eyesight. Changes found in astronauts' eye tissue may cause vision problems, and possibly even blindness. As well as threatening the health of astronauts, this could jeopardize long-haul missions into space. 27 NASA astronauts after they had spent an average of 108 days in space. Four had bulging of the optic nerve, three had kinks in the nerve sheath, and six had flattening of the eyeball.
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