Astronauts have a tendency to experience changes to their vision during long duration missions. This is often seen as one potential obstacle to deep space missions. How do you take control of a landing craft that’s about to bring you down on a Martian field that’s too steeply sloped or rocky to comfort if your vision has deteriorated?
UT Southwestern Medical Center researchers believe that they may have a solution, as published in the Journal of Physiology. They recruited volunteers who had a port known as an Ommaya reservoir placed in their heads as part of a cancer treatment so that the research team could measure intracranial pressure in a variety of positions, including sitting and laying down. Then the team had the volunteers make a series of flights in NASA’s infamous Vomit Comet, making several parabolic flights to simulate weightlessness.
The senior author of the Journal of Physiology paper, Dr. Benjamin Levine, said of the process: “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.”
The researchers found that the intracranial pressure in weightless conditions tends to be higher than when the volunteers are sitting or standing in normal gravity, but lower than when they are laying down. This pressure would be constant for an astronaut on the International Space Station because he or she is in freefall regardless of position.
The team is already working with companies on methods that can counter the effects of weightlessness on intracranial pressure in weightless conditions, such as developing tools that simulate the normal effects of the day/night cycle. One proposed device is a vacuum-like device that applies negative pressure to the lower body and could draw blood away from the head. If successful, these tools will help reduce pressure buildup behind the eyes if astronauts use them while sleeping.
Implications For Human Spaceflight
In reference to the volunteers, who will hopefully win their battle against cancer, Dr. Levine said, “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. 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 future spacefaring civilization should be grateful, too, now that they won’t have to worry about vision problems becoming an obstacle to human progress. If the negative pressure device can successfully counter the intracranial pressure problem enough to reduce or eliminate changes to astronauts’ vision, it removes one objection to long-duration, deep-space missions. Without a way to counter the problem, an astronaut’s vision could change enough that the astronaut becomes ineligible for future spaceflights. If the effect could be mitigated, however, it gives opponents of manned deep space missions one less argument they can use. Now the pilot of our first manned mission to Mars does not have to worry about vision problems when he has to stick the landing.