Astronauts who spend prolonged periods of time in a zero gravity environment may develop serious eye abnormalities due to swelling in the brain.
A new study, published online in the journal Radiology, used magnetic resonance imaging (MRI) to study the eyes and brain of 27 astronauts, all of whom had been on long space missions.
The astronauts were all exposed to microgravity or zero gravity, during an average of 108 days while on various space shuttle missions. Eight of the astronauts then underwent a second MRI after a second space mission lasting 39 days.
The study found that 33 per cent of astronauts with more than 30 days of microgravity exposure experienced expansion of the cerebral spinal fluid space surrounding the optic nerve. 22 per cent had flattening of the rear of the eyeball and 15 per cent were diagnosed with bulging of the optic nerve.
Abnormalities were found in three of the astronauts, including changes to the pituitary gland and its connection to the brain. The pituitary gland, found at the base of the brain, is a gland that secretes important hormones for growth, reproduction and metabolism.
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“These changes that occur during exposure to microgravity may help scientists to better understand the mechanisms responsible for intracranial hypertension in non-space traveling patients,” said Larry A. Kramer, M.D., professor of diagnostic and interventional imaging at The University of Texas Medical School at Houston.
The same symptoms are shown in cases of intracranial hypertension, a swelling in the brain in which no cause is found. Pressure in the brain can lead to swelling of the juncture between the optic nerve and the eyeball, resulting in visual impairment.
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The findings of the study concluded there may be a “hypothetical risk factor and a potential limitation to long-duration space travel,” said Dr. Kramer.
This could pose a problem for future missions, due to the worry of health complications during long missions. A trip to Mars, for example, takes seven months and may be too taxing on the health of astronauts.
Changed in vision have been noted in some International Space Station (ISS) astronauts, according to NASA.
“NASA has placed this problem high on its list of human risks, has initiated a comprehensive program to study its mechanisms and implications, and will continue to closely monitor the situation,” said William J. Tarver, M.D., M.P.H., chief of flight medicine clinic at NASA/Johnson Space Center.
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