What kind of effect do lcd screens have on human eye?

It won’t affect your eyes any more than a CRT, if that’s what you’re asking. Most of them run at around a 75Hz refresh rate, which can give you some full-motion artifacts on fast-paced games. That can make your eyes a little teary or give you a headache. I alternate between a 22” LCD monitor and a 19” CRT all day long, and they both give me about the same amount of eyestrain. If you’re having problems, try turning the room lights up or down (don’t play in an otherwise dark room or in bright light). It also helps to take a break once in a while, but that can be hard to do if you’re really into gaming.