Scientists have developed a hi-tech sleeping bag that could prevent eye problems some astronauts have had while living in space.
In a zero-gravity environment, fluids float inside the head and compress the eyeball over time. This is considered one of the most dangerous health problems affecting astronauts, and some experts believe it could impede missions to Mars.
The sleeping bag balances the fluid in the head and transports it to the feet, controlling the increase in pressure. It was developed by Benjamin Levine, professor of medicine at the Southwestern Medical Center at the University of Texas at Dallas. Levine is working to transfer the equipment to the International Space Station (ISS).
NASA, the US space agency, reported vision problems in more than half of the astronauts who spent at least six months on the ISS. Some developed difficulties in seeing from afar, in reading, and needed help completing space mission experiments.
“We don’t know what the effects might be in the case of a longer trip to space, like a two-year operation on Mars,” said Levine, who is also director of Institute for Exercise and Environmental Medicine.
“It would be a disaster if astronauts were seriously compromised to the point where they can’t see what they’re doing, compromising the mission.”
In 2005, astronaut John Philips began his mission on the ISS with normal vision, also called 20/20 vision, and returned six months later with 20/100 vision. normal eye could see at 100 meters.
Others had less severe versions of the problem. On Earth, gravity pulls body fluids downward every time a person gets out of bed—something known as “unloading.” But in space, low gravity allows half a gallon of bodily fluids to accumulate in the head, putting pressure on the eyeballs.
This can lead to a condition called “neuro-ocular syndrome associated with space travel” (spaceflight-associated neuro-ocular syndrome) or SANS, its acronym in English. This, in turn, can lead to progressive flattening of the back of the eyeball, swelling of the optic nerve, and impaired vision.
“The pressure in zero gravity is always less than the pressure in gravity one. But it’s not as low as when you’re standing. NASA astronauts cannot stand during the flight,” Levine explained to BBC News.
Although the brain pressure of a person lying on Earth is slightly greater than that of someone lying in space, astronauts experience constant pressure and cannot relieve it by standing upright.
“They never have the opportunity to ‘unload’ (the flow of fluids) from the brain. So we asked, ‘can we reintroduce the gravitational gradient’? says Levine.
The sleeping bag is wrapped around the person’s waist, covering the lower body with a solid frame.
A suction device, which works on the same principle as a vacuum cleaner, creates a pressure difference that moves the fluid to the feet. This prevents fluid from accumulating in the brain and “crushing” the eyes.
Some questions need to be answered before this technology is routinely used, such as the amount of time astronauts must spend inside the device each day.
“Does everyone need to do this or just people who are predisposed to develop SANS? Do you need to do this as soon as you hit space, or can you wait to see if your vision changes?” Levine exemplified, speaking of the still unanswered questions. “This sort of thing has yet to be defined.”
But Levine says the creation of the sleeping bag means that SANS may no longer be a health risk in NASA’s future mission to the Red Planet.
People who have had cancer and have survived played a crucial role in clarifying the causes of this medical condition. The volunteers still had the head fits used to give the chemotherapy drugs, and this allowed the scientists to measure the pressure in the brain as they spent a few seconds in flight simulators in zero gravity.
A dozen other volunteers tested the technology itself. Scientists took measurements while they were lying down with and without the sleeping bag. The researchers found that while three days of lying flat was enough to slightly change the shape of the eyeball, no change occurred when suction technology was used.
A team of researchers at Southwestern Medical Center had previously discovered that microgravity caused the heart to shrink in space, potentially causing a condition called atrial fibrillation – a kind of cardiac arrhythmia.
It is possible that the sleeping bag may also help control abnormal blood flow which increases the risk of irregular heartbeat in low severity. Research on this has been published in the academic journal JAMA Ophthalmology.