There's a free program called F.lux that you can install on your computer that will dim your screen for you gradually throughout the day. You don't even notice it. I have it on my computers. Works great. I discovered it last year when I had a really bad optic neuritis. It helps keep people from getting insomnia from the really bright light of a computer screen messing up their circadian rhythm
http://download.cnet.com/f-lux/3000-...-75447318.html