Eye Structure Begins To Change After Thirteen Days In Space
October 24, 2013

Eye Structure Begins To Change After Thirteen Days In Space

[ Watch the Video: How Does Space Travel Affect The Eye? ]

Lee Rannals for redOrbit.com - Your Universe Online

It is widely known that space can have adverse effects on an astronaut’s body over time, and scientists reporting in the journal Gravitational and Space Research say it can even affect their eyes.

Researchers from several institutions, led by Houston Methodist pathologist Patricia Chévez-Barrios, MD, sent mice into orbit aboard the STS-133 space shuttle Discovery mission in 2010 to research the effects of space on the eyes.

During the 13-day study, the team, which also included researchers from NASA Johnson Space Center, examined mouse retinal gene expression throughout the trip, measuring indicators of oxidative and cellular stress. They discovered that these mice experienced changes in eye structure and gene expression during the relatively short excursion.

The scientists found that mice showed immediate evidence of oxidative stress in their retinas when they returned back to Earth. However, the retinas returned to normal after spending seven days back on Earth. They also found oxidative stress in the cornea elevated a day after returning to Earth, but this came back to near-normal levels by the seventh day.

"This suggests oxidative stress in the retina and lens are at least partially reversible under the circumstances of the experiment," said Chévez-Barrios in a statement. "This was after a relatively short time in orbit. We don't know if damage caused by longer periods of oxidative stress will be more severe. Only more studies with longer exposure times may help answer this question."

The study is important for scientists to understand the long-term health effects on astronauts who embark on long-duration missions, such as a trip to Mars or an asteroid. Radiation from the sun can cause extremely damaging chemical reactions in cells, but the Earth’s atmosphere helps shield us from this damage by absorbing much of the radiation.

The International Space Station (ISS) and other spacecraft have shields to help protect astronauts from radiation, but the latest study shows that better technology may need to be developed to prevent damage to astronauts' eyes.

Researchers found that changes seen in cell and tissue shape, along with fluid balance, is similar to what had been reported in previous studies.

A NASA sponsored Ophthalmology study in 2011 found that seven astronauts had experienced eye problems after spending at least six months in space. Doctors in this study saw a flattening of the back of the eyeball, folding of the choroid, excess fluid around and presumed sweeping of the optic nerve.

As for the mice, Chévez-Barrios said the results should be considered preliminary, similar to a pilot study. She added that the findings are plausible based on what scientists know from previous studies on structural changes and damage caused by oxidative stress and changes in the eyes of astronauts returning to Earth. However, additional experiments are needed to confirm the study’s findings.

"These changes were partially reversible upon return to Earth. We also saw optic nerve changes consistent with mechanical injury, but these changes did not resolve. And we saw changes in the expression of DNA damage repair genes and in apoptotic pathways, which help the body destroy cells that are irreparably damaged,” Chévez-Barrios said in a press release.