Scientists have pinpointed why the vision of astronauts deteriorates after long trips in space.
In a study conducted at UT Southwestern Medical Center, researchers found that constant intracranial pressure astronauts experience may be to blame.
For astronauts, the intracranial pressure in zero-gravity conditions is higher when standing or sitting than it is on Earth, but lower during sleep than it is on Earth.
Using a vacuum device to lower pressure for part of each day might prevent the problem.
In the study, researchers measured intracranial pressure on volunteer patients who had a port permanently placed in their head as part of treatment for cancer.
These eight volunteers were flown on NASA flights one-by-one on steep up-and-down maneuvers that created 20-second intervals of weightlessness.
The patients had their intracranial pressure measured during zero-gravity and the research team compared those numbers with the intracranial pressure measurements taken during standard times of sitting, lying face upward and lying with head including downward.
Senior author Benjamin Levine, Ph.D., professor of Internal Medicine at UT Southwestern Medical Center and director of the Institute for Exercise and Environmental Medicine (IEEM), (jointly run by UT Southwestern and Texas Health Resources), said the study was the first of its kind.
“These challenging experiments were among the most ambitious human studies ever attempted as part of the Flight Operations parabolic flight program and changed the way we think about the effect of gravity—and its absence—on pressure inside the brain,” Levine said in a statement.
“The information from these studies is already leading to novel partnerships with companies to develop tools to simulate the upright posture in space while astronauts sleep, thereby normalizing the circadian variability in intracranial pressure, and hopefully eliminating the remodeling behind the eye,” he added.
The results will lead to additional studies on whether it is possible to lower intracranial pressure with a vacuum device that pulls blood away from the head.
Previous research showed that a negative pressure box that snuggly fits the lower body can lower intracranial pressure when applied for 20-minute periods.
The scientists will also be testing the effect of the lower body negative pressure device on eye remodeling when negative pressure is applied for eight-hour periods.
“Astronauts are basically supine the entire time they are in space,” first author Dr. Justin Lawley, Ph.D., Instructor in Internal Medicine at UT Southwestern and a researcher at the IEEM, said in a statement. “The idea is that the astronauts would wear negative pressure clothing or a negative pressure device while they sleep, creating lower intracranial pressure for part of each 24 hours.”
Levine said the negative pressure device research was also used with patients with the ports.
“We are extremely grateful to these brave men and women from around the country who volunteered to let us make these critical measurements on them during parabolic flight,” he said. “They have been through a lot of medical procedures in their lives, and were nonetheless extremely altruistic, desiring to give something back to medical science.”
A change in vision is cited at the number one major health risk for astronauts who spend extended periods of time on the International Space Station.
The study appeared in The Journal of Physiology.