As space missions have increased in length, astronauts began to notice something troubling: their time in space seemed to be causing their eyesight to deteriorate. This wasn't a minor effect. John Phillips, who spent more than six months on the International Space Station, found his eyesight had gone from 20/20 to 20/100 after his mission.

Phillips wasn't the only one. It's now believed that 80% of astronauts suffer from what scientists are calling visual impairment intracranial pressure syndrome (VIIP). The syndrome name describes one of the theories on how the damage takes place, but it's far from being proven.

When Phillips landed he was subjected to a battery of tests including MRIs and retinal scans. These found that while in space, the back of his eyes were flattened and his retinas pushed forward. His optic nerve was also inflamed and his eyes showed choroidal folds, which are essentially stretch marks. Researchers thought this pointed to a build up of pressure in the brain during space flight, which may be due to the low levels of gravity in space. But they have yet to find an effective way to study this theory.

There's a few reasons for this. There's nothing on Earth that can accurately simulate the microgravity of space, so finding a way to measure cranial pressure in space will be essential for figuring out how VIIP is caused. Meanwhile, there are only two ways to test the level of pressure inside a human brain: spinal taps or drilling a hole in the skull. Either of those would be very difficult and dangerous to perform in space. "There's the risk for infection and just doing the procedure, quite frankly, in space is difficult," J.D. Polk, a senior flight surgeon at NASA, told the Washington Post. "Having to anchor somebody and do a spinal tap in space is not something we would relish."

Researchers are trying everything they can to understand the syndrome here on Earth, using methods like tilting bodies downwards to simulate the pressure on the eyes and putting people in parabolic flight, which simulates zero gravity for a few seconds. None of these methods have yet yielded much helpful information.

VIIP is a major roadblock in NASA's plans to send humans to Mars by 2030. That trip would take six to nine months and NASA can't afford to have astronaut's losing their sight halfway through the trip.

But there is some hope. Ross Ethier, a biomedical engineer at Georgia Tech, is designing a device that would draw bodily fluid down into the legs during flight. It's unclear how large and clunky the device would be and how long astronauts would have to wear it each day. There's also the potential that technology like ultrasounds or even a cranial implant could help scientists study the pressure in the brain during space flights without performing risky in-flight surgery.

As of now, our understanding of the effects of microgravity on the human body is still minimal. VIIP is probably the first of many conditions we'll discover as people stay in space for longer periods of time.

Source: Washington Post

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