Just two weeks in space causes changes in eyes

Just 13 days in space may be enough to cause profound changes in eye structure and gene expression, an article in Gravitational and Space Research reports.

Since 2001, studies have shown astronauts are at increased risk of developing eye problems, like premature age-related macular degeneration. Experts suspect the cause is low gravity, heightened exposure to solar radiation, or a combination of the two.

High-energy radiation from the Sun can cause extremely damaging chemical reactions in cells, collectively called oxidative stress. Earth's atmosphere reflects or absorbs much of this radiation and is a much better shield than the thick metal hulls of space shuttles.

To determine the impact of radiation exposure on eyes a group of researchers examined mice following a 13-day trip aboard space shuttle Discovery (STS-133). The researchers examined the eyes and surrounding tissues for broad changes in structure and shape that could relate to low gravity.

Mice returning to Earth showed immediate evidence of oxidative stress in their retinas. But the retinas appeared to return to normal by the seventh day on Earth. An indicator of oxidative stress in the cornea was also elevated one day after mice had returned from orbit, but returned to near-normal levels by the seventh day. But also optic nerve changes consistent with mechanical injury were noted and these changes did not resolve.

The scientists stressed that the strain of mice used in the study are known to be unusually sensitive to light, and that the severity of oxidative, cellular, and tissue problems they saw would probably be milder in healthy human eyes.

From www.sciencedaily.com