NASA Finds that Space Flight Impacts Astronauts' Eyes and Vision

Space flights that last six months or longer can cause changes in astronauts' eyes and vision, according to a study sponsored by NASA. This discovery is having a major impact on plans for a manned flight to Mars. Astronauts' eyes and vision are a top priority of the NASA's Space Medicine research team, according to Acting Chief Terry Taddeo.

The study examined seven astronauts in depth and found eye structure and vision abnormalities in all of them. The most common structural change was flattening of the back of the eyeball. Changes in the retina, the light-sensitive area at the back of the eye, and the optic nerve were also found. In some astronauts these changes persisted long after their return to Earth.

In a separate NASA survey of 300 male and female astronauts, about 23 percent of short-flight and 49 percent of long-flight astronauts said they had experienced problems with both near and distance vision during their missions. Again, for some people vision problems persisted for years afterward.

NASA is concerned that on a three-year trip to Mars astronauts could develop serious vision damage, or even blindness, that could not be corrected or treated during the flight. Researchers are now working with space station astronauts to measure their intraocular pressure and obtain ultrasound images of their eyes during flights. Astronauts also receive these two tests before and after all missions, along with optical coherence tomography (which magnifies cross-section views of parts of the eye), magnetic resonance imaging, and fundus photography (which records images of the retina and back of the eye).

One theory is that the abnormalities found in the seven astronauts were caused by fluid shifts toward the head that can result from living in microgravity conditions for an extended time. So far, NASA researchers cannot say exactly what causes the eye and vision problems.

It's been known for years that near vision can change in space. Even John Glenn had a pair of "space anticipation glasses" onboard his capsule. Today astronauts use glasses that improve visual sharpness, also called visual acuity.