Back in July, we ran a story here about astronaut Scott Kelly and the problems he was having with his eyesight after spending a year in space.
Four months ago, it was a mystery, but now scientists are pretty sure they know the cause, the online magazine Inverse reports.
They had a name for the syndrome that resulted in the vision loss: visual impairment intracranial pressure, or VIIP. And NASA scientists have been worried about it for more than a decade, as people spend longer periods in space. Almost two-thirds of astronauts on long missions on the International Space Station are affected, but VIIP hasn't been understood until now.
Cerebrospinal fluid, or CSF, is the clear fluid surrounding the brain and spinal cord. But in space the absence of gravity eliminates the pressure needed to regulate the fluid. The result is a flattening of the eyeball, along with optic nerve protrusion and inflammation.
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