Study Identifies Cause Behind Visual Impairment In Astronauts Assigned To Long-Duration Missions
Astronauts who serve on lengthy missions in space could be affected by a visual health issue because of the volume changes in the clear fluid around the brain and the spinal cord. During the last decade, specialists at NASA started to observe a pattern in the visual impairment issues that astronomers have.
The study, presented on Nov. 28 at the Radiological Society of North America annual meeting, suggests that space missions could have a negative impact on the eyesight of astronauts. Blurry vision is one of the most common symptoms that were described as part of this study. When a trend was observed in this direction, specialists started to test the astronauts who reported experiencing these symptoms.
Vision Impairment Syndrome In Astronauts
The syndrome is also known as visual impairment intracranial pressure, and it was observed in approximately two-thirds of the astronauts who took part in long-duration missions on the International Space Station.
"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," noted Noam Alperim, lead author of the study.
First Quantitative Evidence
Prior to this research, scientists attributed this visual impairment syndrome to the shift of vascular fluid toward the upper body, which is a common occurrence for astronauts who spend their time in a microgravity environment. However, this study analyzed another hypothesis.
The research is based on the idea that changes in the volume of cerebrospinal fluid or CSF, which is linked to nutrients circulating and removing waste materials in the spinal cord and the brain, could actually have an impact on astronauts. The CSF serves the purpose of dealing with changes in the hydrostatic pressures, but microgravity poses new problems to this functionality.
Because of the lack of posture-related pressure changes, when in space the CSF cannot accomplish its functions, which leads to post-flight flattening to the eyeballs in the case of astronauts who have taken part in long missions. This study is the first to give quantitative evidence related to the role of CSF and the way a person's visual system structure changes when the body is exposed to a microgravity environment.
Other health issues have been previously correlated to space travel. One of them is shrinking and weakening of the spinal muscles, which leads to backaches and injuries.
"Paraspinal lean muscle mass, as indicated by the functional cross-sectional area, decreased from 86 percent of the total paraspinal muscle cross-sectional area down to 72 percent, immediately after the mission," the researchers noted in a study published in the journal Spine.
Muscle soreness and joint pains were also documented in astronauts who have spent long periods of time on the ISS, along with skin issues consisting of a burning sensation whenever any physical activity was conducted, even walking.