Science & Technology

Astronauts Have Eye Problems in Space, and Swimming Goggles Might Help

The classic image of an astronaut involves a high-tech suit and a fishbowl-inspired helmet on their head. But that's just when they're out in space; during day-to-day life in the International Space Station, astronauts just wear normal clothes. That might change, at least if the latest research has anything to say about it. Scientists may have figured out how to keep astronauts' eyes healthy in space — and it involves swimming goggles.

The Eyes Hate It

Space is really, really bad for the human body. Besides the radiation exposure and the always-looming possibility that you could be sucked out into the cold vacuum of space, microgravity itself takes a toll on astronauts' muscles, bones, and organs. It weakens their cardiac muscles and makes their hearts more spherical, and leads to a loss of bone strength on par with the effects of osteoporosis. Humans evolved beneath the gentle push of Earth's gravity, and without that resistance, the body's equipment gets weaker.

Microgravity takes a toll on the eyes, as well. Astronaut eye problems are so common, there's a name for the phenomenon: spaceflight-associated neuro-ocular syndrome, or SANS. After an extended time in space, a majority of astronauts experience vision problems, including farsightedness due to a flattening of the eyeball, swelling of the optic nerve, and damage to the nerves of the retina. But while astronauts can try to stave off weakening bones and muscles through exercise, nobody's quite sure how to prevent outer-space eye troubles. Scientists aren't even sure what causes them.

They do have some hunches, though. The researchers behind a study published last month in JAMA Opthalmology thought that these issues might be caused by pressure: specifically, too much intracranial pressure, or pressure inside the skull, and not enough intraocular pressure, or pressure inside the eyes. This difference in pressure is known as the translaminar pressure gradient, and it's nothing new to eye medicine. Glaucoma, the group of eye conditions that can damage the optic nerve, can also be caused by an off-kilter pressure differential between the head and the eyes, but in the opposite direction.

But the research wasn't just to find out if their hunch was correct. The team also wanted to find out if they could fix this pressure problem, if it did exist. There are a few ways they could try to balance this pressure differential, but two stood out as the easiest: exercise, which had been shown to decrease intracranial pressure, and swimming goggles, which had boosted intraocular pressure in previous research. Operation Michael Phelps in Space could officially begin.

Just Keep Swimming

They had 20 men come into NASA's Johnson Space Center in Houston on three separate occasions, each time completing either strength or cardio exercises. They did every exercise on their backs, tilted back 15 degrees with their heads below their feet in a position that's often been used to simulate the effects of microgravity. Half of the men wore swimming goggles.

So what happened? Well, there was good news and bad news. The bad news was that exercise decreased intracranial pressure, but it also decreased intraocular pressure, so it didn't fix the translaminar pressure gradient. The good news was that wearing swimming goggles successfully increased intraocular pressure, helping to mitigate that pressure gradient. If further studies get the same results, it may make swimming goggles a cheap and easy way to ease astronaut eye problems.

There are caveats, however. In an editorial comment on the study, Andrew G. Lee pointed out that we've measured intraocular pressure in astronauts on the ISS, and we've never seen levels that are too low. And like we mentioned previously, eye pressure that's too high is linked with glaucoma. Still, scientists have been unable to measure intracranial pressure on the ISS, and it's the difference between eye and head pressure that these researchers were after. If exercise with swimming goggles helps reduce that difference, it might be a worthwhile fix after all.

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Learn more about life in outer space in "Packing for Mars: The Curious Science of Life in the Void" by Mary Roach. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer May 1, 2019

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