Issues such as dry eyes, eye fatigue, things like that, which can over time cause gradual issues.

I'm sure those 4-8 hours were broken up, so you weren't, as I said, "staring at a monitor all day." I game at work, I game at home, I also read, and I can tell you, the monitor is worse to look at continuously for long times.

Neither's good for you, really. And both can be aided with some common sense (i.e. lighting around you in relation to the monitor or book, taking breaks, stuff like that). I'm not remotely suggesting kids can't play multiple hours of games without serious impact, so long as it's done smart. I'm just saying that the idea that books could cause the same impact as computers - neither of which can actually cause nearsightedness, really - is daft. It's obvious that staring at a bright screen for four hours straight is going to cause more eye strain than reading a book for four hours (assuming all things are equal, i.e. you're not trying to read a book in very poor lighting).