Pressure is on to find the cause for vision changes in space

IMAGE:NASA astronaut Michael Hopkins, Expedition 37 flight engineer, performs ultrasound eye imaging in the Columbus laboratory of the International Space Station. European Space Agency astronaut Luca Parmitano, flight engineer, assists... view more

Credit: NASA

A change in your vision is great when referring to sparking a creative idea or a new approach to a challenge. When it refers to potential problems with sight, however, the cause and possible solutions need to be identified.

The human body is approximately 60 percent fluids. During spaceflight, these fluids shift to the upper body and move across blood vessel and cell membranes differently than they normally do on Earth.

One of the goals of the Fluid Shifts investigation, launching to the International Space Station this spring, is to test the relationship between those fluid shifts and a pattern NASA calls visual impairment and intracranial pressure syndrome, or VIIP. It involves changes in vision and the structure of the eyes and indirect signs of increased pressure in the brain, and investigators say more than half of American astronauts have experienced it during long spaceflights.

Improved understanding of how blood pressure in the brain affects eye shape and vision also could benefit people on Earth who have conditions that increase swelling and pressure in the brain or who are put on extended bed rest.

"Our first aim is to assess the shift in fluids, to see where fluids go and how the shift varies in different individuals," says Michael B. Stenger, Ph.D., Wyle Science Technology and Engineering Group, one of the principal investigators. "Our second goal is to correlate fluid movement with changes in vision, the structure of the eye, and other elements of VIIP syndrome."

A third aim is to evaluate application of negative pressure to the lower body to prevent or reverse fluid shifts and determine whether this prevents vision changes. Researchers are collaborating with Roscosmos (the Russian Federal Space Agency) on that part of the study because the Russians have a lower body negative pressure device, the Chibis suit, aboard the station. Recently published ground-based data show that applying negative pressure over the lower body helps shift fluids away from the head during simulated spaceflight, adds co-investigator Brandon Macias, Ph.D., of the University of California San Diego.

For a variety of reasons, the Chibis suit cannot be moved from the Russian Service Module of the space station. Therefore, to conduct these unique experiments, crew members will transport medical research equipment from the U.S. side of the station to the Russian module. Moving things around in space is a lot more complicated than it is on the ground, says co-investigator Douglas Ebert, Ph.D., of Wyle Laboratories. In this case, it will take more than four hours of crew time to move and set up the equipment, one or two hours for the experiment itself, and another four or so hours to move everything back.

That effort will pay off though, in terms of new and important data that may lead to the answers of how and why VIIP happens and how to prevent or treat it during spaceflight.

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Pressure is on to find the cause for vision changes in space