I ran across this interesting vignette from Astronaut Cmdr. Hadfield (his Twitter account here) on how sight changes in space including the flattening of eyeballs, swelling around the optic nerve and the random flashes of light seen by astronauts.
Cmdr. Hadfield lived on board the International Space Station for 5 months, performing experiments and doing perhaps, the best public relations job for space travel of any astronaut in history. One of my favorite videos made outside of Earth’s atmosphere was Cmdr. Hadfields cover of David Bowie’s Space Oddity. Its well worth five minutes of your time.