In recent years, NASA physicians have become increasingly alarmed regarding a tendency among astronauts to suffer from blurred vision upon their return to Earth. The immediate culprit appeared to a flattening of the back of the eyeball combined with aggravation of the optic nerve, but what precisely has been causing the changes has been a genuine mystery. Now however, in a study of 12 astronauts published in the Radiological Society of North America, researchers believe they have found the cause.
“Scientists previously believed that the primary source of the problem was a shift of vascular fluid toward the upper body that takes place when astronauts spend time in the microgravity of space. But researchers led by Dr. (Noam) Alperin recently investigated another possible source for the problem: cerebrospinal fluid (CSF), the clear fluid that helps cushion the brain and spinal cord while circulating nutrients and removing waste materials. The CSF system is designed to accommodate significant changes in hydrostatic pressures, such as when a person rises from a lying to sitting or standing position. However, the microgravity of space presents new challenges.
“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,” Dr. Alperin said.”
Note: Problems with vision have been rapidly climbing the scale of “space dragons” that some maintain must be dealt with before people can ever go to Mars. And unlike some of those “dragons” this one appears to be real. If confirmed, this study is a significant first step in coming coming up with countermeasures to a problem which worsens with extended spaceflight.
Somewhat frustratingly, the most obvious countermeasure, spin-induced artificial gravity, will likely be overlooked yet again.