Blinded By Space
About 385 million years ago, our ancestors made their way from the oceans onto land. A landmark event in the evolutionary history of life on Earth.
There are various hypotheses as to why this happened, but there isn’t a definitive answer. Some researchers believe that an increase in visual capability may have been the driving factor. By looking at the fossil record they note that the size of eyes tripled before the transition. Enlarged eyes coupled with the fact that light travels faster on land than underwater increased their visual range, allowing the migrant species to spot prey on land more easily.
Whether this truly was the cause cannot be proved. In any case, significant changes followed once the migration happened. Changes that eventually led to the evolution of humans and other species.
Today, the next frontier we look towards is space. And we have already taken the first steps, just like our aquatic ancestors did millions of years ago. The astronauts that have made the journey into space are, in a way, like the first vertebrates that crawled their way onto land from the ocean.
This time around, however, we may not have the vision we need to cross over and it will be much harder for life to adjust.
Before we become a space-faring civilization we must first come to terms with our limitations. The biggest one being, our bodies.
Having evolved on Earth, it is expected that humans will find the harsh conditions of outer space difficult to survive in. Radiation exposure in space can cause direct damage to the DNA, increase the risk of cancer, and can affect the nervous system.
Being in microgravity environments, as much of space travel would entail, can cause bone density loss, muscle atrophy, and can impair cognition.
Vision loss is another major cause for concern that has been identified recently.
Though it is commonly referred to as ‘space blindness’, no astronaut has experienced a complete loss of vision. But the effects of trips longer than the ones astronauts have experienced so far have the potential to be much more harmful.
Based on anecdotal reports and post-flight tests, NASA was aware of visual impairments caused by space travel for the last forty years, but they believed these weren’t permanent changes.
John Phillips, who was aboard the International Space Station in 2005 for six months also thought the same. During his time on the ISS, he began to experience a deterioration in his vision. He expected that once he was back on Earth, his normal vision would return. Post-flight physical examinations revealed that his vision had gone from 20/20 to 20/100. This meant, what a person with normal vision could see clearly from 100 feet away, he had to be at a distance of 20 feet to be able to read.
Further tests and scans had shown that there were physical changes to his eyes such as the flattening of the back of his eyeballs, inflamed optic nerves, and choroidal folds, which are wrinkles or lines on the back portion of the retina.
These are some of the symptoms among others, that would show up in a number of astronauts over the years. And a few would experience long-lasting changes. Tests performed by NASA on some astronauts ten years after their return from space still showed symptoms like flattened eyeballs.
Growing concern led NASA to look more closely into the issue. They were able to narrow it down to pressure around the eyes causing the physical changes.
Due to the absence of gravity, fluids that would normally be pulled down are rushed to the head.
Intracranial pressure (ICP) is the pressure created by the presence of cerebrospinal fluids (CSF) in the skull. A recent study has shown that astronauts that stayed longer in space had increased levels of CSF within the skull. It was believed that the increased pressure was causing the symptoms that were seen.
Elevated ICP seems to be a strong candidate as other factors increase ICP as well, such as the CO2 levels on the International Space Station and the high sodium diet of astronauts.
But proving this hypothesis is difficult because a direct measurement would involve performing a spinal tap, a procedure where a needle is inserted into the spinal column to extract cerebrospinal fluids. Performing such a test during spaceflight may be a little complicated.
One of the reasons it is hard to come up with answers is due to the difficulty of creating an environment on Earth that could mimic the effects of space. But researchers have still tried to get the answers they need.
A small study was performed in 2007, to test ICP elevation with four people. They simulated weightlessness for a period of twenty-five seconds and found that ICP had not been elevated.
This was the opposite of what was expected. But even if it was shown that microgravity caused ICP to elevate, it wouldn’t have been the end of the research. This is because some astronauts do not experience vision problems even if they have been on long-duration space trips.
It appears that personal physiology needs to be accounted for as well. Astronaut Clayton Anderson, for instance, did not experience any vision deterioration. He has stated that, based on studies conducted by NASA, he has a protein in his body that seems to have protected his vision.
All of this has led to the conclusion that the Spaceflight-Associated Neuro-Ocular Syndrome (SANS), is unique. Its symptoms are varied. And the precise cause is still unknown.
SANS is something that would need to be addressed before undertaking longer missions, like a Mars trip for example.
There are ongoing studies to understand the syndrome more clearly. Currently, the aim is to either find a way to prevent it or at least provide countermeasures. Devices to redistribute the flow of fluids in the body and artificial gravity are some of the methods being proposed.
Astronauts that have faced these issues have said they wouldn’t trade their time in space for anything. And that isn’t surprising at all.
On a grander scale, these are the first few pages in the next big chapter of life as we know it. Baby steps towards a new environment. The problems like SANS are the growing pains we must deal with.
But on a personal level, it could be that getting the chance to see the Earth from such a point of view must be worth it, even if it meant not being able to see anything else clearly again.
