Tag Archives: vision

Heavier astronauts more likely to have vision issues in zero-G

An analysis of the physical characteristics of astronauts who develop vision problems after long missions in weightlessness has found that heavier body weight increases the risk.

The research team examined data collected by NASA from astronauts who had made long-duration space flights (averaging 165 days). The data included the astronauts’ sex and pre-flight height, weight, waist and chest size, as well as information about post-flight eye changes. The findings were related to body weight, not body mass index. They found that none of the female astronauts analyzed—who weighed less than the males—returned to Earth with symptoms of SANS. To rule out sex differences as a cause for the disparity, the researchers also examined the men’s data separately. “Pre-flight weight, waist circumference and chest circumference were all significantly greater in those who developed either disc edema or choroidal folds. This was still true when only the male cohort was analyzed,” the researchers wrote. “The results from this study show a strong relationship between body weight and the development of ocular changes in space.”

That such small differences in weight can make such a difference suggests again that adding just a small amount of artificial gravity, rather than 1g, might mitigate these issues. No tests of this however have ever been done, mostly because the engineering is complex and expensive. For humans we would need to build a vessel large enough that any rotation would be unnoticed. If the vessel is small it must rotate faster and the body’s inner ear gets confused. However, if we only need to simulate a tiny amount of gravity the spin rate can be reduced, simplifying the engineering.

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Vision problems from weightlessness

This article provides an excellent review of the vision problems caused by long term exposure to weightlessness, including the efforts to study the problem on Earth.

Bottom line:

Before a human trip to Mars — a journey of six-to-nine months that NASA says it wants to achieve by the 2030s — researchers agree that VIIP [the name given to this problem] must be understood much better. VIIP could be the first sign of greater dangers to the human body from microgravity. “We’re seeing the visual and neural, ophthalmic manifestations of it,” Barratt said. “I’m fairly certain this is a bit more global than that.”

Richard Williams, the chief health and medical officer at NASA, agrees that what we do not know about VIIP still poses the biggest threat. Ironically, one of the only ways to get more knowledge is spend more time in microgravity. “The longer we stay in space, the more we’re going to learn,” Williams said.

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