Things were different when they returned from the International Space Station.

Researchers have found changes to the structure of the eyes of astronauts returning from the International Space Station.

The phenonomenon is called space flight-associated neuro-ocular syndrome, or SANS, and it's been a subject of NASA research for several years, according to a University of Houston press release. And now a UH optometrist has published a paper quantifying some of the changes using a technique called optical coherence tomography imaging.

"We studied pre-flight and post-flight data from 15 astronauts who had spent time aboard the space station and detected changes in morphology of the eyes," said Nimesh Patel, an assistant professor at UH. "All of them had good vision before and after the flight, but many of them had a change in structures of their eyes."

He explained the specific changes: "The findings of this study show that in individuals exposed to long-duration microgravity, there is a change in the position of the Bruch membrane opening, an increase in retinal thickness closer to the optic nerve head rim margin, and an increase in the proportion of eyes with choroidal folds."

According to the release, researchers hypothesize that the changes seen in astronauts are a result of microgravity-associated orbital and cranial fluid shifts.

Patel said he hopes someday his findings will have applications for patient care.

The findings were published in the journal JAMA Ophthalmology.

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