Brain scans of Nasa astronauts who have returned to Earth after more than a month in space have revealed potentially serious abnormalities that could jeopardise long-term space missions.
Doctors examined 27 astronauts who had flown long-duration missions with the United States’s space agency and found a pattern of deformities in their eyeballs, optic nerves and pituitary glands.
The problems are similar to those caused by intracranial hypertension, a rare medical condition that occurs when pressure inside the skull rises and presses on the brain and the backs of the eyes.
Medical crews at Nasa and space agencies in Europe, Russia, Japan and Canada are now screening astronauts before, during and after missions. Astronauts who had flown on the space shuttle and international space station reported changes to eyesight, with some seeing worse and others better. Brain scans revealed that seven of the 27 astronauts had a flattening of the back of one or both eyes. By making the eyeball shorter, this made the astronauts more long-sighted, which in some cases reduced or corrected their short-sightedness.
Dr Larry Kramer, who led the study at the University of Texas’s health science centre in Houston, said the impact on astronauts’ eyesight might become “a new limiting factor” to long excursions into space. His results, published in the journal Radiology, suggested the abnormalities were worse and more frequent in astronauts who spent longer in weightless, or microgravity, conditions.
Kramer said: “Consider the possible impact on proposed manned missions to Mars, or even the concept of space tourism. Can risks be eventually mitigated? Can abnormalities detected be completely reversed?”
Four of the astronauts had swelling around the optic nerve, which could affect the transmission of signals from eye to brain and, in the longer term, cause nerve fibres to die off.
The changes add to the effects of astronauts’ bone loss and muscle wastage, known about for decades. —