Space Vision
 
Nov. 17, 2015: Traveling in space has many odd effects on the human body. One
of the strangest has to do with vision.
 
After spending some time on the International Space Station, many astronauts
discover that they cannot see as well as they do on Earth.  The effect is so
well known that members of the crew routinely pack "space glasses" to correct
their vision in orbit.
 
https://www.youtube.com/watch?v=xtq3b_HYg9w#t=11
 
Many astronauts report a blurring of their eyesight in microgravity.
Researchers are trying to get to the bottom of this phenomenon before
astronauts travel to Mars and beyond.
 
Researchers still aren't sure what causes the problem, but they would like to
solve it before humans travel beyond low-Earth orbit. A trip to Mars could
take at least three years -- five times as long as a mission to the station.
So it's important to learn about the adverse effects of microgravity on vision
and develop ways to counter them.
 
Christian Otto of the Universities Space Research Association in Houston,
Texas, is one of the researchers trying to get a clearer understanding of
"space vision." He is the Principal Investigator of the Ocular Health study
now underway on the space station.
 
An accomplished off-road triathlete with an interest in human performance in
extreme environments, Otto is well-suited to this PI role. He once toted an
ultrasound machine up Mount Everest to study the effects of oxygen deprivation
on intracranial pressure. Now, with the Ocular Health study, he's remotely
conducting similar tests on astronauts.
 
"Testing astronauts before, during, and after their missions to the station
shows us their status preflight and helps us identify changes that result from
the environment and microgravity on the station," explains Otto.
 
On the space station, the body's fluids, particularly the blood supply, shift
toward the head much like what happens on Earth when you lie down. Therefore,
it is hypothesized that the pressure inside the skull increases. That increase
in intracranial pressure is believed to be transmitted to the eye and optic
nerve, leading to changes in eye structure and visual acuity.
 
Optic Disc Edema (ODE) -- swelling of the optic disc -- is the most critical
change. If it persists, it can lead to a loss of peripheral vision and
eventual blindness. Astronauts have experienced only mild ODE to date, but no
one knows how severe it could become on a Mars expedition.
 
"Data from this study will help researchers develop countermeasures for and
reduce susceptibility to issues like ODE," says Otto. "It will help us develop
targeted treatments to prevent problems."
 
Adding preliminary data from the Ocular Health study to data from previous
Vision Impairment and Intracranial Pressure (VIIP) studies, Otto and his team
have made some interesting discoveries.
 
"Around 70% of 33 International Space Station crewperson subjects have
experienced mild VIIP, and we are finding that men are affected about twice as
severely as women.
 
ODE is measured on a scale of 0-5, with 1 being the least effected and 5 being
the most. Six out of seven subjects with ODE were grade 1, while the 7th
subject had a grade 3 eye. All seven subjects that developed clinical grade
ODE were men.
 
Results from the Ocular Health study will help doctors better understand
disorders such as glaucoma and Idiopathic Intracranial Hypertension (IIH) that
can plague people back on Earth. The latter is a condition in which
cerebrospinal fluid pressure rises and remains elevated for a long time,
causing severe headaches that even the strongest pain medications can't
touch.  Like glaucoma, the condition sometimes leads to vision loss and
blindness.
 
Says Otto,"This study will tell us more about noninvasive measurement of
intracranial pressure. The way doctors measure it now is through a spinal tap
or making a burr hole in the skull and inserting an intraventricular monitor."
 
"We are pushing the envelope in several areas of terrestrial clinical
medicine. NASA's Ocular Health study is providing new insights in neurology,
neurosurgery, ophthalmology, and cardio-vascular physiology. The clinical
community is very excited."
 
For more on studies on the International Space Station, go to ww
.nasa.gov/station
 
 
Regards,
 
Roger

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