Actors Jim Sturgess and Ed Harris had a medic on standby while shooting scenes for The Way Back - because chemicals used to create a fake blizzard burned their eyes.
The pair spent weeks filming in gruelling conditions in the Sahara desert for the movie, about a group of prisoners who trek to India after escaping from a Russian jail during World War II.
A special high-powered snow machine was used to re-create the icy conditions faced by the men - and Sturgess reveals the pain he and his co-stars suffered as they shot take after take.
He tells Total Film magazine, "In the film we get caught in a snowstorm and it was worse than being in a real one. They were firing this stuff at us at 100 miles an hour out in the woods using big wind machines and it was like this chemical, snowy-looking stuff that got in your eyes and burned your eyeballs.
"There was a medic on set who would have to pull all this s**t out of your eyes and put eye-drops in, then we'd do it all over again."