I guess it's also about distance. Monitors are right in front of our eyes. I probably wouldn't hurt looking a tree or hill, or anything that is outside because

I guess it's also about distance. Monitors are right in front of our eyes. I probably wouldn't hurt looking a tree or hill, or anything that is outside because they are at a distance. And of course you aren't going to stare at them for long periods of time. Staring at monitors/screens is different.