Ive used a PC almost everyday of my life since I was about 5 and i never have problems, maby as someone said above its like allergies, some people get it, some don't, also yes, turning down the brightness can help . I spend at least 2 Hours a day on it, as i can't go hang around with mates during school time as they don't live near me, So i don't go out unless we arrange to go to town or something :]