Just 13 days in space may be enough to trigger profound changes in the eye's structure and gene expression, writes an article in Gravitational and Space Research.
Since 2001, studies have shown that astronauts face a higher risk of developing eye problems, such as premature age-related macular degeneration. Experts suspect the cause is low gravity, increased exposure to solar radiation, or a combination of the two.
Oxidative stress and solar radiation
High-energy solar radiation can cause extremely harmful chemical reactions in cells, collectively known as oxidative stress. Earth's atmosphere reflects or absorbs a large portion of this radiation and provides far better protection than the thick metal hulls of space shuttles.
To determine the effects of radiation exposure on the eyes, a group of researchers studied mice following a 13-day voyage aboard the space shuttle Discovery (STS-133). The scientists examined the eyes and surrounding tissues for extensive structural and morphological changes that may be associated with low gravity.
Changes to the retina and cornea
Mice that returned to Earth showed immediate evidence of oxidative stress in their retinas. However, the retina appeared to recover to normal by the seventh day back on Earth.
An oxidative stress marker in the cornea also rose one day after the mice returned from orbit, but had nearly returned to normal levels by the seventh day. However, changes to the optic nerve, consistent with mechanical injury, were also observed and did not resolve.
The researchers emphasised that the strain of mice used in the study is known to be unusually sensitive to light, and that the severity of the oxidative, cellular, and tissue problems is likely milder in the eyes of healthy humans.
From www.sciencedaily.com
