Astronauts who spend extended stints in outer space typically suffer from blurred vision — but even after 55 years in space, the reasons why are still unclear. Now, new research has identified cerebrospinal fluid (CSF) as root cause for why this condition plagues astronauts. Known as visual impairment intracranial pressure, or VIIP, the syndrome has worried NASA scientists for over a decade, as humans begin to spend longer durations in orbit. The findings were presented today at the annual meeting of the Radiological Society of North America.

Astronauts aboard the International Space Station face all kinds of physical consequences they’d never really encounter in a gravity-filled atmosphere. There’s not just muscle atrophy, but muscle stiffening and loss of bone density (which can all mean a possible increase in height. VIIP reportedly affects almost two-thirds of astronauts who undertake long missions on the ISS, but hasn’t been extensively studied or understood until now.

CSF is the clear fluid that surrounds the brain and spinal cord. VIIP arises when a microgravity environment leaves that fluid without pressure to regulate it, leading to eyeball “flattening,” as well as optic nerve protrusion and inflammation. The changes were discovered by comparing MRI scans of seven ISS astronauts before and after their extended missions in space.

Space has a physically flattening affect on the eyeballs.
Space has a physically flattening affect on the eyeballs.

“People initially didn’t know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to earth,” said Dr. Noam Alperin, the lead author of the study, at the meeting.

Now that we know what’s causing the damage, NASA can get to work trying to develop successful countermeasures, though we don’t yet know what form those might take. Early identification seems to be key in terms of preventing irreversible damage. Beyond that, NASA will just have to test whatever physical safeguards its researchers come up with over the next decade or so of long-term space missions. VIIP is one of many physical obstacles - arguably the most serious of which is radiation — we still need to find a work around if we’re ever going to conduct manned missions to Mars, let alone colonize it.

Photos via Radiological Society of North America, Flickr / NASA's Marshall Space Flight Center