Ask YC: What is the best lighting source for a room with no windows?

We moved to our new offices, and they are great, except for the fact that I now work in a room with no windows. There is only an overhead fluorescent light.

I usually program for 10-12 hours a day, and have now noticed that my eyes hurt, and I am getting bags under them.

What is the best way to light the room so that my eyes are happy again?