My job forces me to sit in front of the monitor or laptop screen for more than 8 hours a day. is it better to wear a powerless glass (zero power) to reduce the impact?

Use anti glare: pain glasses will not make any difference , rather use anti glare glasses or screen cover for lap top

Glare: My assumption is that you're either talking about cutting down glare or you were told that computer screens were "bad for you." No study has linked computer screens to poor eye health other than getting some dry eye by keeping them open longer than usual. You can cut down glare by putting of those filtering screens over the screen. No need for glasses here. Hope that helps.