Scientists have always wondered why astronauts experience blurred vision when returning from a space mission. After years of conjecture, many scientists believe they have found the answer to why astronauts often have visual problems upon returning to earth's surface.
Researchers at the University of Miami's Miller School of Medicine devised a study to look at volume changes within an astronaut's brain and spinal cord. MRI scans were taken of astronauts before and after seven long-duration missions into outer space. These scans were contrasted with other MRI scans of astronauts who went on nine short-duration missions.
After using algorithms to show similarities in the fluid volume of the spinal cord, eyes, and brain of these astronauts, researchers concluded that all of these astronauts suffered from visual impairment intracranial pressure (VIIP). About two-thirds of all astronauts who took long trips to the International Space Station (ISS) were diagnosed with this disorder.
Noam Alperin, the head researcher on this project, said that scientists had no idea what was causing the astronauts' changes in vision as recently as 2010. The most popular theories at the time had to do with the movement of vascular fluid towards the upper body. Astronauts often experience this rush of blood to their heads in microgravity, so scientists theorized that this fluid must remain in the upper part of the body upon returning home.
Instead of vascular fluid, this new study suggests the real culprit of these eye symptoms is cerebrospinal fluid (CSF). CSF is a transparent fluid that works to move nutrients and waste from the brain through the spinal cord.
Scientists now theorize that the CSF system is confused by the antigravity environment of outer space. On earth, the CSF system can easily regulate changes in posture with reference to gravitational force, but the CSF systems of astronauts cannot effectively regulate posture changes because there is no gravity to help orient it.
Further tests on the astronauts who went on long-term missions revealed their eyes were flattened. Researchers also found that these astronauts' eyes had inflamed optic nerves. Astronauts who only went on short-term missions had healthier eyes than those who went on long-term missions.
Astronauts on long-term missions were found to have an increase of CSF in many skull cavities. This increase in fluid was particularly noted in regions close to where CSF is produced by the brain.
Although the CSF was found to change dramatically, there were no changes noted in the actual structure of the brain. Scientists say that the grey matter and white matter volume remained constant for all astronauts tested.
This study is crucial for preparing astronauts for potential trips to Mars in the ensuing years. Since trips to Mars will require even longer-term missions, doctors need to be aware how to effectively prepare and treat astronauts' eyes. Some in the medical community actually worry that traveling to Mars under current conditions could lead to blindness.
NASA publically announced this data at the Radiological Society of North America's annual meeting. Specific details of this study are available on NASA's official website.