Astronauts on space missions should start wearing swimming goggles to prevent the affect of weightlessness on their sight, according to new research from NASA.

Astronauts on long missions at the International Space Station often experience changes to their eyes that can last for years, including impaired vision.

Scientists have found that wearing goggles that create mild pressure around the eyes can counteract the problem, caused by a drop in pressure inside the eye.

These could be swimming goggles or the type of safety glasses commonly worn by sportsman and constructors.

Astronauts on space missions could start wearing swimming goggles like those in the picture to prevent the affect of weightlessness on their sight, according to new research. The picture shows astronaut Anne McClain who is currently working on the International Space Station

Up to 75 per cent of astronauts develop changes to their eyes, including decreased visual sharpness.

Many astronauts experience poorer sight - some leave on missions with perfect site yet return needing glasses.

This phenomenon, a medical condition known as Space flight-associated neuro-ocular syndrome (SANS), is caused by the lack of gravity in space which reduces the fluid pressure inside the eyes.

In a new study, scientists showed that by giving astronauts safety glasses, like those worn in snow sports, protected vision by boosting the pressure of fluid inside the eye known as Intraocular pressure (IOP).

SANS is a significant clinical concern at NASA and symptoms include 'cotton wool spots', which are fluffy white spots on the retina, and the swelling of the optic nerve.

This condition is seen in approximately one out of three International Space Station astronauts.

Dr Jessica Scott, of the Universities Space Research Association, Houston, explained: ' Swimming goggles firmly compress the skin around the eye.'

'These findings suggest modestly increasing intraocular pressure with swimming goggles could be used to mitigate spaceflight-associated neuro-ocular syndrome.

'Elucidating the mechanistic underpinnings of SANS is important to protect the health of astronauts and continued human space exploration.'

Astronauts on long missions at the International Space Station often experience changes to their eyes that can last for years, including impaired vision. Scientists found that wearing goggles that create mild pressure around the eyes can counteract the problem (stock image)

Magnetic resonance imaging (MRI) scans suggest pressure changes in the brain, with spinal fluid caused by weightlessness perhaps partly to blame.

The latest findings were based on tests on 20 individuals at NASA's Johnson Space Centre in Houston.

Ten of these participants were given swimming goggles to wear and the others going eye wear free.

Dr Scott said: 'The addition of swimming goggles was associated with modestly increased pressure, which could reduce some of the adverse effects on the eye of long-duration spaceflights.

'Confirmatory studies are required to determine the appropriate duration and intensity of artificial increase in IOP in space flight to modulate SANS.

'In addition, evaluation of the safety of prolonged or daily goggle use is needed.

She added: 'These findings need to be replicated in spaceflight to determine whether increasing eye pressure with swim googles is safe and effective.'

It is known long term exposure to zero gravity causes a host of health problems, one of the most significant being loss of bone and muscle mass.

Over time these can impair astronauts' performance, increase their risk of injury, reduce their aerobic capacity and slow down their cardiovascular system.

But previous researcher also found that most of the changes to the human body from extended spaceflight returned to normal shortly after a return to Earth.

The risks to their sight on prolonged periods in space, however, has only recently emerged.

NASA hopes to put man on Mars within 15 years after being given an order by Donald Trump to speed up their space operations.

Last month administrator Jim Bridenstine said the president's desire to put humans back on the Moon by 2024 will enable a mission to the Red Planet by 2033.

The full report of the findings were published in JAMA Opthalmology.

A previous study on retired astronaut Scott Kelly (right) and his identical twin brother Mark found that most of the changes to the human body from extended spaceflight returned to normal shortly after a return to Earth. The risks of travel to sight has only recently emerged