Although the results of space missions are often well documented, the effects of these flights on the astronauts themselves is often not reported, though recent research has shed some light on this.
A new study sponsored by NASA shows that space flights lasting six months or more can cause a "spectrum "of changes in astronauts" visual systems, with some problems, including blurry vision, appearing to persist long after astronauts" return to Earth.
The results are currently impacting plans for long-duration manned space voyages, such as a trip to Mars, explained a team including ophthalmologists Dr Thomas H Mader, of Alaska Native Medical Center, and Dr Andrew G Lee, of The Methodist Hospital, in Houston, Texas.
The report, published in Ophthalmology, the journal of the American Academy of Ophthalmology, involved studying seven astronauts, all of whom were aged around 50 and had spent at least six continuous months in space.
Every astronaut reported that their vision became blurry, to varying degrees, while on the space station, with vision changes usually beginning around six weeks into the mission and persisting in some astronauts long after their return.
The expert note that the eye abnormalities appear to be unrelated to launch or re-entry, as they only occurred in astronauts who spent extended time in microgravity.
Examination of the seven astronauts revealed several abnormalities, including the flattening of the back of the eyeball, folds in the vascular tissue behind the retina and excess fluid around and presumed swelling of the optic nerve.
Dr Mader said that, in the space program"s early days most astronauts were younger, military test-pilots who had excellent vision, though today"s astronauts tend to be in their 40s or older.
"This may be one reason we"ve seen an uptick in vision problems. Also, we suspect many of the younger astronauts were more likely to "tough out" any problems they experienced, rather than reporting them," he added.
by Martin Burns