Eye specialist and MD of Butterflies Healthcare, James Sutton, is warning against watching stereoscopic 3D content for more than 2 hours at a time.
The UK optometrist explained that "a lot of people do say when they come out of the cinema that they are aware they've done something different with their eyes, even if it's not to the extent of a headache or sickness, but they're aware that it was hard work to watch."
"I'd have said that was more than enough," Sutton added. "I would worry about people spending hours doing it, I must say."
Sutton's concerns are pretty much relative to hardcore gamers whose gaming sessions are well beyond the 1 hour and 30 minutes time length of a typical movie.
"When you create 3D, the two images have to be separated slightly, so your eyes are having to look at things slightly removed from each other; that's what gives you the 3D depth. That's an artificial situation, because you're trying to look at something coming out at you that isn't really coming out at you," Sutton explained.
"It's quite a lot of work for you to do that for a sustained period… There's a proportion of people that find that, for the prolonged period of time that they're having to do it, it will cause eye-strain, as they're working too hard to create what is, in effect, a visual illusion."
In related news, Sony recently updated their Terms of Service to advise users to take "regular breaks while watching 3D video or playing stereoscopic 3D games," and to ensure that those breaks are "long enough to allow any feelings of discomfort to subside."