ISS experiment: Why does space change vision?

Chuck Bednar for – @BednarChuck

A new experiment, scheduled to launch to the International Space Station in the spring, plans to take a long look at vision changes often experienced by astronauts during extended spaceflights, NASA officials announced on Tuesday.

The cause of these vision issues is called visual impairment and intracranial pressure syndrome (VIIP), and according to the US space agency, it involves changes not only in the sense of sight but the structure of the eyes and indirect signs of increases pressure on the brain.

A shift in fluids

The human body is roughly 60 percent fluids, and in space, these fluids shift to the upper part of the body, moving across blood vessels and cell membranes in a different way than they do on Earth. The upcoming Fluid Shifts study will test the relationship between this phenomenon and VIIP, which reportedly affects over half of all US astronauts during extended spaceflights.

Learning more about how blood pressure in the brain affects vision and eye shape could also help those on Earth dealing with conditions that increase swelling and pressure in the eye, as well as though who have been placed on extended periods of bed rest.

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“Our first aim is to assess the shift in fluids, to see where fluids go and how the shift varies in different individuals,” explained Dr. Michael B. Stenger of the Wyle Science Technology and Engineering Group, one of the principal investigators of the Fluid Shifts project.

The second goal, Stenger added, is to “correlate fluid movement with changes in vision, the structure of the eye, and other elements of VIIP syndrome.” A third objective is to evaluate the application of negative pressure to the lower body, with the intention of preventing or reversing fluid shifts and determining if this can prevent vision changes from occurring.

Working with the Russians

Recently published ground-based data suggests that applying negative pressure to the lower body is able to shift fluids away from the head during simulated spaceflight, said Brandon Macias, a co-investigator on the study and a postdoctoral fellow at the University of California San Diego.

Chibis suit

Expedition 36/37 Flight Engineer Luca Parmitano in the Chibis lower body negative pressure device aboard the International Space Station. (Credit: NASA)

NASA scientists are collaborating with colleagues from the Russian Federal Space Agency (Roscosmos) on the third part of the project, as the Russians have a lower body negative pressure device known as the Chibis suit already on board the ISS. The Chibis suit cannot be moved from the Russian Service Module of the space station, meaning that medical equipment required for the experiments will be transported from the US side of the ISS to the Russian end.

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As Dr. Douglas Ebert explained, moving equipment in the microgravity environment of space is far more complicated than it would be on the Earth. In this instance, it will require four hours of crew time to move and set up the equipment, another one or two to conduct the experiment, then another four hours to move everything back. However, he and his colleagues are confident that it will be worth the effort, and that they will find the answers they’re looking for.

“It’s important to know what is happening because we may have to tailor preventive measures to each individual,” Stenger said. “We also may find that an exercise that is good for bone or muscle is bad for elevated intracranial pressure. Exercise is great for preserving work capacity and the musculoskeletal system but may be a contributor to increased pressure in the head.”

Curretly, the Chibis suits are only used by cosmonauts to prepare for re-entry, but if the Fluid Shifts study reveals that lower body negative pressure can help reverse fluid shifts towards the head and prevent the symptoms of VIIP, they may be uses more frequently on long missions.

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Astronaut Scott Kelly and cosmonaut Mikhail Kornienko, space station veterans who have been selected for a one-year mission to the ISS, will have measurements recorded for the investigation soon after their arrival, at the halfway point, and again 45 days before their departure. That data should help provide a comprehensive look at what is happening with fluid shifts and VIIP.


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