Who would have thought taking an earth-bound creature and sending him or her into outer space in a tin can, in zero gravity conditions, would have any adverse effects on the body? Oh wait…everyone? You all thought that? Well, you were all right!

Doctors, examining 27 astronauts on the long-term effects of space travel, recently found “a pattern of deformities in their eyeballs, optic nerves and pituitary glands that remains unexplained,” reports Raw Story. Deformities were found in 7 of the subjects, or just over 25%.

While they don’t know the specifics of what produces these effect, the layman’s explanation is that your body swells in zero gravity, which can warp some of your more sensitive parts. In nerd speak, “All of the findings could be explained by a buildup of cerebrospinal fluid in the brain,” says Dr. Larry Kramer.

This has big implications for the future of long term space travel, from manned trips to Mars to the space tourism imagined by Richard Branson. Governments may be reluctant to send people into space if the effects can’t be mitigated. As such, the deformities are now being studied by space programs across the world.

Volker Damann, head of Crew Medical Support Office at the European Space Agency in Cologne, Germany, says “If you produce more cerebrospinal fluid, or resorb less, you increase the pressure in your skull. Since your skull is bone, there’s nothing that gives way, with one exception, and that is the eyeballs. This leads to a flattening of the eyeball, and so your vision changes.”

Flattening eyeballs and impaired vision don’t sound like much fun. At the same time, when you’re talking about sending an organism into outer space, with no gravity and none of the environmental conditions that shaped its existence over millions of years, a little wonky vision seems like the least you could expect.

Plus, Raw Story notes, “symptoms seen in Esa astronauts have abated within weeks or months of touching down.”

A little wonky vision, and it’s only temporary? Pssssh, please—where do I sign up?