September 22, 2011
Astronauts Could Lose Sight During Long Space Trips
NASA is looking into a possible eye condition that could blind astronauts if they were to undertake a multiyear mission to the Red Planet, reports the Los Angeles Times (LA Times).
The space agency discovered that some astronauts who have been living aboard the International Space Station for many months at a time have developed the vision problem, concerning them that future missions to Mars and beyond could blind their astronauts.
Research by the American Academy of Ophthalmology suggests that a trip to Mars would be enough to blind most astronauts, giving NASA enough reason to ask scores of researchers to study the issue. The agency has even gone as far as putting special eyewear on the ISS to help those affected with vision problems.
“We are certainly treating this with a great deal of respect,” Dr. Richard Williams, NASA's chief health and medical officer, told Mark K. Matthews of the LA Times. “This [eye condition] is comparable to the other risks like bone demineralization [loss] and radiation that we have to consider.... It does have the potential for causing mission impact.”
A NASA survey of 300 astronauts discovered that nearly 30 percent of those who have gone on shuttle mission -- which last usually two weeks -- and 60 percent of those who have spent 6 months aboard the ISS have reported a gradual blurring of eyesight.
Williams said he believed the actual number for space station crew vision blurriness was 35 percent. However, he did not dispute the severity of the problem.
The disorder, similar to papilledema (optic disc swelling that is caused by increased intracranial pressure), is thought to be caused by increased spinal-fluid pressure on the head and eyes due to microgravity, although that is currently only speculation.
The problem has gone away in most astronauts once they returned to Earth. But a recent study by the National Academies noted there had been “some lingering substantial effects on vision,” and that astronauts were not always able to qualify for future missions due to the problem.
At least one astronaut has never regained normal vision, according to Williams.
NASA has long worried about the effects spaceflight could have on astronauts, especially those that could last 3 years or longer -- which would be seen in a Mars round-trip. Until recently, the major concern has been cosmic radiation and loss of bone mass due to microgravity.
Although a relatively new problem, NASA has been studying the vision issue since about 2005, when one of their astronauts made the remark of such a problem.
“You didn't hear about it at all until you had one fellow come back [from space] and had problems and was very open about it. His openness led to other people reporting the same,” Garrett Reisman, a former astronaut who spent three months aboard the station in 2008, told Matthews.
Most of NASA´s research has been on seven anonymous astronauts who have shown symptoms, including one whose eyesight became so bad by his third month on the ISS that he could “only see the Earth clearly while looking through the lower portion of his progressive reading glasses,” according to a summary of a paper published in the medical journal Ophthalmology.
“No one has been in space long enough to know how bad this papilledema can get,” Dr. Bruce Ehni, a neurosurgeon at Baylor College of Medicine, told the LA Times.
Ehni, who has worked with NASA on this issue, said papilledema can lead to blindness if left unchecked, so it is important to solve this riddle before we decide to send astronauts on longer missions. When such a mission does happen, “you can't end up having a bunch of blind astronauts,” he said.
Reduced gravity can cause many problems, and is the likely the main cause of the eye trouble. It is known to cause short-term problems in the body -- known as Space Adaptation Syndrome -- including spatial disorientation, nausea and vomiting. This is mainly caused by body fluids rising to the head and putting pressure on the brain and eyes.
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