Space is not good for your eyes — unless you are nearsighted, in which case it might help a bit.

Trips to weightlessness can squash the eyeballs of astronauts, swell the optic nerves and blur vision — changes that often persist long after the astronauts return to weightbound Earth. That is one more health effect that NASA will have to worry about before astronauts venture farther out into the solar system.

“When you’re talking about missions that might be two years round trip, it has to be in the back of your mind that this could be a potential limiting factor,” said Dr. Larry A. Kramer, a professor of diagnostic imaging and intervention at the University of Texas Health Science Center at Houston.

Dr. Kramer and his colleagues have put more than 35 astronauts into high-resolution magnetic resonance imaging machines. This month in the journal Radiology, they reported their findings on the first 27 astronauts they examined.