70% of astronauts who spend time on the International Space Station (ISS) expertise swelling in the back of their eyes, inflicting blurriness and impaired eyesight each in house and once they return to Earth. Sometimes, it’s everlasting. Understanding the way in which microgravity impacts the eyes, and the human physique as a complete is a vital a part of preparations for future lengthy-length spaceflights to the Moon and Mars. In an effort to know the reason for these eye issues, researchers on the Medical University of South Carolina used MRI scans of twelve ISS astronauts to measure the intracranial venous system (veins that flow into blood to the mind) earlier than and after flight. They’ve decided that there’s a robust connection between the swelling of those veins and the onset of eye bother.
Poor eyesight is simply one of many medical challenges going through people in house. When not having to struggle in opposition to Earth’s gravity, muscle tissue change into weak and bone density decreases, whereas the excessive radiation surroundings of house threatens to trigger lengthy-time period ailments like most cancers. The ISS is essentially designed as a microgravity laboratory, and most of the experiments carried on the market are medical in nature, with astronauts themselves as prepared check topics – all the things discovered from these research helps hold them and their friends secure. As a consequence, a wealth of medical information has been gathered that may scale back the danger to future spacefarers.
The impact of spaceflight on the eyes is called spaceflight-related neuro-ocular syndrome (SANS). SANS is so frequent, in line with Dr. Mark Rosenberg, one of many examine’s authors, that “it’s gotten to the point where astronauts actually carry extra pairs of glasses when they go into space. They know that their vision is going to be deteriorating up there, and they’ve even started calling them space anticipation glasses.”
NASA astronaut Chris Ferguson has his eyes imaged utilizing ultrasound on the Johnson Space Center Flight Medicine Clinic, 2011, in Houston. Credit: NASA.
The bodily adjustments within the eyes embody flattening of the globes, harm to the retinas, and the swelling of nerves within the eyes. For some astronauts, the eyes get well inside weeks of returning to Earth, however the therapeutic course of can generally take for much longer.
The root reason for SANS, in line with the paper Rosenberg and his colleagues produced, appears to be correlated with veins swelling behind the eyes. Weightlessness causes the distribution of blood within the physique to vary, with fluid shifting in direction of the top and eyes greater than is common on Earth, the place gravity reduces the movement to those areas.
These outcomes suggest “individuals with increased venous sinus compliance may be at increased risk of developing SANS,” and due to this fact pre-screening may also help astronauts perceive the dangers to their eyes earlier than they ever go away the Earth.
There continues to be, in fact, extra to be taught. For one factor, the staff hopes to do extra analysis on how SANS dangers may differ between women and men, utilizing a bigger pattern measurement of astronauts (the present analysis relies on 2 feminine and ten male astronauts). They’d additionally like to put in a cell MRI machine on the ISS, which might permit them to do mind scans in house. The submit-flight scans used within the present analysis leaves open the chance that the adjustments they see within the intracranial venous system happen on return to Earth, somewhat than in orbit, and the staff would love the chance to rule out that chance. The staff additionally believes their analysis will helpful for understanding eye issues for people right here on Earth. What is discovered in house has purposes in medical science proper right here at dwelling.
Celia Spell, “Living in outer space: Changes in blood flow volume may be at the heart of worsening eyesight” MUSC Catalyst News.
Rosenberg MJ, Coker MA, Taylor JA, et al. “Comparison of Dural Venous Sinus Volumes Before and After Flight in Astronauts With and Without Spaceflight-Associated Neuro-Ocular Syndrome.” JAMA Netw Open. 2021.
Featured Image: Astronaut Serena Auñón-Chancellor examines her eye aboard the International Space Station with distant assist from medical doctors on the bottom (2018). Credit: NASA.
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