Space travel takes a heavy toll on the human body. As NASA’s Twin Study shows, long-term stays in space result in a loss of muscle and bone density. There are also notable effects on the cardiovascular, central nervous system, and endocrine systems, as well as changes in gene expression and cognitive function. There’s also a visual impairment known as Spaceflight-Associated Neuro-Ocular Syndrome (SANS) that many astronauts reported experiencing after spending two months aboard the International Space Station (ISS). This results from increased intracranial pressure, which puts strain on the optic nerve and causes temporary blindness.
Researchers are looking for ways to diagnose and treat these problems in preparation for future missions that will involve long-term extra-Earth stays and space transits. A multidisciplinary team of researchers led by the University of Western Australia (UWA) has developed a breakthrough method of measuring cerebrospinal fluid pressure that could reduce the SANS risk for astronauts on long-term spaceflights. This research could have applications to the many efforts to create a human presence on the moon this decade and manned missions to Mars in the next decade.
The team was led by William H. Morgan, an ophthalmology professor specializing in glaucoma and diabetic/vascular retinopathies. He is also Director of the UWA Center for Visual Science (COVS) and Executive Director of the Lions Eye Institute in Perth, Australia. He was accompanied by researchers from the International Center for Radio Astronomy Research (ICRAR), the International Space Center (ISC) and Murdoch University. The study describing their findings was published in npj Microgravity, a publication maintained by Nature Partner Journals (npj).
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Professor Bill Morgan, director of the Lions Eye Institute, in the laboratory. Photo credit: UWA
As Prof Morgan explained in a recent UWA press release, human bodies evolved to counteract the effects of gravity by forcing blood up into the head:
“In microgravity, this can lead to increased mean CSF pressure, which affects the retina and impairs vision and other important functions. The strength of the pulsations in the small veins of the retina should in principle depend on the CSF pressure. All blood vessels experience tiny pulsations that come from the heartbeat.”
Until recently, intracranial pressure could only be measured through a spinal tap, a burr hole in the skull, or other invasive procedures that are painful, risky, and difficult to perform in microgravity. For their study, Morgan and his collaborators used a special eye camera to measure tiny changes in pulsation in subjects placed in different positions on a tilt table. This mimicked the effects of variable gravity on CSF pressure, simulating what astronauts experience transitioning to microgravity and back.
According to co-author Danail Obrezhkov, associate professor at the International Center for Radio Astronomy Research and director of the International Space Center, her team has developed the first non-invasive method of measuring pressure changes in cerebrospinal fluid that can be safely performed in space. This outcome study could be crucial in overcoming a type of blindness that often develops in astronauts on long-duration space flights. Said Obrezhkov:
“So-called space-associated neuroocular syndrome is one of the most serious risks faced by astronauts on long-haul flights and one that NASA has identified as a significant challenge for future human missions to Mars. Tilt-table experiments on Earth are the only way to controllably change the gravitational force on the human body, and have allowed us to change CSF pressure in small, defined increments. It also forced us to develop systems that can be used in any posture, which is portable, small, handheld devices that are essential if such systems are to be deployed in space.”
Astronauts in freefall on the International Space Station. Photo credit: NASA/ESA
Their findings could also lead to the development of wearable, handheld devices that could monitor intracranial pressure in astronauts, providing an inexpensive and low-risk means of quickly diagnosing SANS. It could also lead to the development of new treatments that mitigate the effects and ensure astronauts maintain healthy vision during long-term stays in space. This study is part of a larger research constellation examining the long-term effects on muscle, bone, and organ health that could lead to new treatments that will facilitate human space exploration (and perhaps even colonization).
Further reading: UWA