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As the majority of humans on planet Earth, we spend all of our time with the same physical and atmospheric conditions. So it makes sense that the human body has been biologically engineered through adaptation and evolution to function optimally under the Earth’s gravity, and not, for instance, the weightlessness of outer space. When astronauts boldly venture into the depths of our solar system, the absence of gravity takes a serious toll on their bodies: decompression of the spinal cord can make space travelers grow taller, bones and muscles become weaker, and the heart can even become smaller in certain cases. Now that astronauts are spending more and more time on extended space missions, many of them come home to find that they cannot focus their eyes as well as before.

According to NASA, many astronauts with normal 20/20 vision discovered that they required prescription glasses for the first time after returning to Earth. Some of these astronauts were told that they would no longer be able to participate in space flights, and others were told they would be unable to pilot even small private aircraft. So what exactly is causing these astronauts to experience sudden vision changes?

A 2012 study using magnetic resonance imaging (MRI) examined the eyes and brains of 27 astronauts who spent an average of 108 days in space aboard the International Space Station or NASA’s space shuttle. Researchers discovered optical abnormalities similar to those that can occur in individuals with intracranial hypertension — a potentially severe condition in which excess pressure builds up inside the skull. One third of the astronauts examined displayed expansion of the cerebrospinal fluid space around the optic nerve, and six patients showed flattening in the rear of the eyeball.

Acting Chief of Occupational Health Branch at NASA’s Johnson Space Center, William Tarver said that the findings are suspicious — but not conclusive — of intracranial hypertension (IHT). Many researchers at NASA postulate that IHT in astronauts is a result of fluid shifts that occur throughout the body while spending prolonged periods in microgravity environments.

Astronauts have been encouraged to monitor the health of their eyes quite carefully in recent space missions. Chris Hadfield, former commander of the International Space Station, explains in a video for the Canadian Space Agency that astronauts are trained to use multiple instruments to measure and examine their eyes while in space. Ultrasound technology helps the astronauts observe their corneas and optic nerves, while other devices, like a tonometer, can estimate the pressure of the eyeball, or even send images of the eyes to optometrists back home on Earth.

Are you experiencing any abnormal changes in your vision after an intergalactic voyage? Okay, probably not. But even stationary earthlings need regular eye exams to maintain sharp, healthy vision! Contact Silverstein Eye Care Centers today at (816) 358-3600 or request your appointment online. We can serve you at our convenient location in Independence/Kansas City.

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