Why astronauts become visually impaired on longer space missions

New York: Astronauts usually suffer from visual problems when they go for a longer space mission.

A new research finds that the volume changes in the clear fluid which is found around the brain and spinal cord is the cause of visual impairment in astronauts.

According to the study scheduled to be presented at the annual meeting of the Radiological Society of North America (RSNA) on Monday, flight surgeons and scientists at the US space agency NASA said astronauts had blurry vision.

The study have revealed the cause of the impairment is that among several other structural changes, flattening at the back of their eyeballs and inflammation of the head of their optic nerves.

The syndrome which is known as visual impairment intracranial pressure (VIIP), was reported in nearly two-thirds of astronauts after long-duration missions aboard the International Space Station (ISS).

Study lead author Noam Alperin said, "People initially did not know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to Earth".

The team led by Dr Alperin, professor at University of Miami's Miller School of Medicine, found that cerebrospinal fluid (CSF), the clear fluid that helps cushion the brain and spinal cord while circulating nutrients and removing waste materials was the main cause of the syndrome.

Dr Alperin noted, "On Earth, the CSF system is built to accommodate these pressure changes but in space, the system is confused by the lack of the posture-related pressure changes".

The results showed that compared to short-duration astronauts, long-duration astronauts had significantly increased post-flight flattening of their eyeballs and increased optic nerve protrusion.

(With IANS inputs)