Scientists Finally Find Reason Why Astronauts Might Go Blind In Space

The astronauts are out for lengthy missions. As a result, they suffer from visual problems. Now, scientists have finally found the reason behind the risk of going blind in space-volume changes in the clear fluid that surrounds the brain and spinal cord.

Scientists have long feared that astronauts might go blind when they go for lengthy space missions, like going to Mars for space exploration. Over the past decade, flight surgeons and scientists at NASA saw a pattern of visual impairment in astronauts who were involved in long space missions.

Some astronauts suffered from blurred vision. Upon further assessment of the condition, it revealed that there were structural changes in the eyes like flattening of the back of the eyeballs and inflamed optic nerve heads.

Dubbed as visual impairment intracranial pressure (VIIP), the syndrome was reported by about two third of astronauts after spending time on a long-term mission aboard the International Space Station (ISS).

"People initially didn't 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," Noam Alperin, study author and professor of radiology and biomedical engineering at the University of Miami Miller School of Medicine in Miami, Florida, said in a press release by the Radiological Society of North America.

What Happens In Space?

In the past, experts have previously linked the eye problem with a shift in the vascular fluid toward the upper part of the body. This usually happens among astronauts who spend time in microgravity.

However, the researchers investigated another possible cause of the visual disturbance -- the cerebrospinal fluid (CSF). This fluid acts as a cushion in the brain and spinal cord where nutrients and oxygen are circulated, while waste products are removed. The CSF is designed to adapt to pressure changes like when a person sits down, stands up or lies down. Unfortunately, during microgravity in space, the system is confused because of the lack of posture-related pressure changes.

"The research provides, for the first time, quantitative evidence obtained from short- and long-duration astronauts pointing to the primary and direct role of the CSF in the globe deformations seen in astronauts with visual impairment syndrome," Dr. Alperin added.

Irreversible Damage

The findings of the study have shown that astronauts who spent time in long-duration missions in space had significantly greater post-flight increases in the volume of the CSF in the bony cavity of the skull, which holds the eye. Moreover, they also have greater volume in the cavities of the brain where the fluid is produced, BBC reports.

Though the sample size is small, the results of the study shed light on the importance of preventing such complications during space exploration missions. When these eye problems and changes are not diagnosed early on, they may lead to irreversible damage to the eyes.

"If the ocular structural deformations are not identified early, astronauts could suffer irreversible damage, as the eye globe becomes more flattened, the astronauts become hyperopic, or far-sighted," Alperin said.