Possible cause of microgravity vision problems identified

Scientists think they may have located the cause of the vision problems experienced by nearly two-thirds of all astronauts after long missions in weightlessness.

Prof Alperin has been looking at another potential source of the problems – the cerebrospinal fluid (CSF). This helps cushion the brain and spinal cord, and can accommodate the changes when a person moves from a lying to a standing position. “In space the system is confused by the lack of the posture-related pressure changes,” Prof Alperin explained.

The team performed high-resolution MRI scans before and shortly after spaceflights for seven long-duration astronauts. They compared the results with nine astronauts who flew into orbit for short stints on the space shuttle. The results showed that long-duration astronauts had significantly greater post-flight increases in the volume of CSF within the bony cavity of the skull that holds the eye, and also in the volume of CSF in the cavities of the brain where the fluid is produced.

The sample size is small, and the study has not yet been peer reviewed, so these results must still be taken with some skepticism.

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.