Its funny. I have three desktops in the house - two are PC's. None of the other ones hurt my eyes. I can use them for many hours. But whenever I use the iMac for more than an hour my eyes start to hurt - especially when reading. I've had this white iMac for three years now. When I first bought it, I found the screen far too bright6 so I always have it on the very lowest brightness setting. But I've never really gotten accustomed to the screen. Its recently started to develop the infamous vertical lines, so I dunno if that maybe that's what's hurting my eyes?