Bad for the eyes? (Image: NASA/Rex Features)

Space flight may be bad for your eyesight. Changes found in astronauts’ eye tissue may cause vision problems, and possibly even blindness. As well as threatening the health of astronauts, this could jeopardise long-haul missions into space.

Larry Kramer of Texas Medical School in Houston and colleagues carried out MRI scans on 27 NASA astronauts after they had spent an average of 108 days in space. Four had bulging of the optic nerve, three had kinks in the nerve sheath, and six had flattening of the eyeball.

The changes match those seen in people with idiopathic intracranial hypertension, a rare condition in which the pressure of blood and other fluids is abnormally high in the brain. People with the condition experience headaches, nausea, vomiting and visual problems including blindness.


In space, the alterations are probably caused by living in free-fall. “One potential mechanism is that blood which normally pools in the legs is shifted toward the skull, raising pressure,” says Kramer.

The findings tally with the results of a survey of 300 astronauts carried out last year. Deteriorations in vision were reported by 29 per cent of astronauts on short-term missions, and 60 per cent on long-term missions.

Mission to Mars

“If astronauts are exhibiting these changes after only 100 days in space, what will happen on a three-year flight to Mars?” asks Jason Kring, who studies human performance in extreme conditions at the Embry-Riddle Aeronautical University in Daytona Beach, Florida.

Deteriorating vision could seriously impair astronauts’ ability to carry out routine mission tasks, including monitoring displays and navigating the rocky landscape of Mars, says Kring. “This possibility, combined with what we already know about how microgravity affects muscles and bones, paints a very bleak future for human space flight unless we start to develop effective countermeasures.”

Kramer says that NASA has the matter in hand. In the wake of the study, all astronauts now have regular brain scans. This includes those yet to travel into space, providing a baseline from which any changes would be obvious. He also believes it might be possible to identify astronauts’ risk of eyesight damage from medical data before sending them into space.

Journal reference: Neuroradiology, DOI: 10.1148/radiol.12111986.