Honestly, you should be taking breaks. Spending 8+ hours a day on the computer is typical for somebody working hard, but taking a break every once in awhile is still essential.

In fact, I've heard a lot of people say that the 30-30 rule has helped them be even more productive. Spend 30 minutes doing hard work on the computer, and then 30 minutes off letting your brain relax.

Good idea.. I'll have to try that.

Seeing as plenty of people often use a computer that much or longer on a regular basis (not counting breaks to eat or go to the bathroom, obviously), I'm not really convinced it's just the how long you use a monitor. I'd suggest talking to an ophthalmologist for real advice.

That said, I think the usual line is to take a ten minute break every hour. Should be good for your legs, too. But really, talk to an ophthalmologist.

Do you have a glossy screen? Switching from glossy to matte helped my eyes a lot.

I also use Flux on my mac, so perhaps that helps.

+1 for Flux I use it for over a year and I can't live without it

There are some programs you can download to help reduce eye strain - they will remind you every so often (20-40 minutes) to do some eye exercises. I find this helps me if I am having sore eyes - especially looking a few inches above the monitor into the distance (20+feet).

I also find that if I am wearing glasses, going to contacts helps, and vice versa.

I use the zenburn theme for everything. In emacs, xmonad colors, my terminal colors, in everything. It's very easy on the eyes.

have you seen a doctor? sounds like you may need glasses or something... your symptoms seem extreme to me.

do you have a nice big monitor?

Getting outside and looking far distances a couple of times a day (walking/cycling) gives my eyes enough exercise. Maintaining focus at one point for extended periods kills my eyes.