In early October, NASA published a press release concerning intracranial pressure. When Scott Kelly and Mikhael Kornienko carried out their one-year mission in 2015-16, intracranial pressure was estimated with devices to check fluid pressure in and sound waves produced by the inner ear.
While the data from the mission is still being analyzed, NASA said there is no "pathologically large increase" in intracranial pressure, but it could still be contributing to astronauts' visual impairments. The agency is planning to look at this issue in more detail on the space station, using other techniques such as ultrasound.
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"There is definitely an accumulation of cerebral spinal fluid within the space behind the eye, but we don't understand what is causing that," said Michael Stenger, lead visual impairment and intracranial pressure with technical services company KBRwyle, in a NASA statement. "Elevated venous pressure or a change in lymphatic drainage may sequester fluid behind the eye, thus causing a compartment syndrome."
For his part, Thirsk (who is now retired) said the causes must be found and resolved long before NASA embarks on a mission to Mars, which the agency says it wants to do around the 2030s. With current technology, it will take months to get there and back -- and the crew must wait at the Red Planet for the most favorable time to return, when the Earth and Mars are closest. "If six months can produce a visual impairment, what about 2.5 years?"
Image (top): Karen Nyberg images her eye with a fundoscope during Expedition 37 in 2013 (NASA)
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