Being an astronaut must be one of the coolest jobs there is. Blasting into space to explore new worlds, floating around weightlessly and viewing earth from afar … in the realm of invigorating work experiences, could it get much better?

But NASA doctors are learning more about a recently discovered drawback to the job. Turns out extended time spent in conditions with very little gravity, known as microgravity, affects many astronauts’ eyes and certain parts of the brain. A recent article in the journal Radiology details what doctors found after performing M-R-Is on astronauts who’ve spent at least 30 days in microgravity.

The scans showed many of these astronauts have at least one of the following differences in their anatomy: eyeballs that are somewhat flattened on the back, enlarged optic nerves with cerebral spinal fluid reservoirs around them, and alterations in the pituitary gland and its connection to the brain.

Some of these conditions can lead to vision problems. Changes like these are normally seen in people who have increased pressure inside their heads, but NASA doctors say they aren’t absolutely sure astronauts are experiencing that heightened pressure in space.

Past studies have reported vision changes and different alterations to the eyes in some astronauts as a result of space missions. For now, they’ll keep watch on these issues in space travelers and hope to learn more.

What they uncover could help not only other astronauts, but also people who experience similar problems here on Earth. More information also will help NASA evaluate whether living in outer space or on other planets will ever be possible for humans.

For now, NASA doctors say these issues won’t keep astronauts … not even those already exhibiting the changes … from going into space. Three, two, one … liftoff!