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Space Travel Damages Optic Nerves of Astronauts

Photo By Vadim Sadovski via Shutterstock


While astronauts get to see the far reaches of space which few people would barely have the chance to do in their lifetimes, there is a physical trade-off for the space travelers -- their vision becomes impaired.

Live Science reported that the optic nerves – the two stalks of nerve tissue that erupt forward from the brain and slip between gaps at the back of the eyeball -- which are the transmitters that link people to the power of sight become damaged. The tissues at the back of their eyes tended to look warped and swollen weeks after they returned to Earth.

Vision problems

A research, published on January 11 in the JAMA Ophthalmology Journal, said that almost half of the 15 astronauts who had orbital freefall in space missions for six months developed significant vision problems.



But many of the astronauts already had pre-existing eye damage before the trip which they likely acquired from previous missions. Their Bruch membrane openings, which are the gaps at the back of the eye through which the optic nerve travels, moved deeper into the eye after long-term missions. It was swollen significantly after the return of the astronauts to Earth.

One possible explanation behind the swelling, according to researchers, is that the eye’s internal pressure increased while the astronauts were in space. However, after some time, the surrounding tissues got used to the new pressure. But when they returned to Earth where there is gravity, the pressure could have quickly drained away. The internal tissues of the eye could have become irritated and deformed because of the rapid change.

No solution yet

The researchers do not offer yet a solution to the problem. It is also unclear if the problem is within the capacity of NASA to solve, although definitely, it is an issue that the space flight program must think about since its workforce is being asked to go on longer stints in outer space.

David Zawieja, a regents professor at Texas A&M University’s College of Medicine, is studying the problem for NASA. The problem could have some gender links because it does not affect female astronauts, KBTX reported.

Because of the problem, the astronauts’ vision becomes blurry by about 10 to 12 feet in front of them. But their vision returns to normal once they return to Earth.


Photo By Vadim Sadovski via Shutterstock


The scientists are now studying how changes in the fluid pressure in a person’s head, like the cerebrospinal fluid that cushions the brain from shock, could affect vision. They are also studying coronary artery function, Houston Chronicle reported.

In a November 2017 risk report submitted by the Johnson Space Center in Houston, it noted that few data exist to determine the extent or cause of the Space Flight-Associated Neuro-ocular Syndrome. As part of the study, the researchers launched 20 male mice to the International Space Station in August to discover why the vision problem affects men only. They expect to have results in the latter part of 2018.

They are also considering that the syndrome could be caused by the increase in vascular fluids, like blood and lymph, in the head. The fluid – estimated at 68 ounces or about the size of a two-liter soda bottle – moves from the legs of an astronaut to this head while he is in space, NASA explained.

In the book “Endurance,” Scott Kelly, the first American astronaut to spend a year continuously in space, wrote that after his first long-duration flight that lasted 159 days, doctors found his optic nerve swollen and choroidal folds, similar to stretch marks, on his eyes.

There are other eye problems the astronauts experienced such as the flattening of the eye shape which was discussed in a 2011 study published in the Ophthalmology journal.


Optic atrophy

According to Bel Marra Health, optic atrophy is the end stage of several conditions which can cause optic nerve damage. If there is any significant damage or degeneration of the optic nerve because of any cause, it can result in loss of vision.

At the highest risk are those who suffer from poor blood supply to the optic nerve. The most common demographic affected are the elderly. Optic atrophy may also be caused by shock, radiation, toxic substances, trauma, a disease of the brain, central nervous system ailments, stroke, a brain tumor, and glaucoma.

Optic atrophy may develop over time from any disease that can compromise the ganglion cell function, a type of neuron found near the inner surface of the retina. But the most common causes are glaucoma, retrobulbar neuritis, traumatic optic neuropathy, and central retinal vein occlusion.

The symptoms include blurred vision, difficulties with peripheral vision, problems with central vision, difficulties with color vision or contrast, and reduction in vision sharpness. To prevent optic atrophy, doctors advise careful management of blood pressure, particularly among older individuals. Injury to the face should be prevented, avoid drinking home-brewed alcohol, and undergo annual eye exams to check for glaucoma.

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