Are you exposed to lots of flourescent lights at work? If they are 50Hz they can cause you eyestrain as you may be susceptible to the flicker – if you don’t have much natural light you can try a normal desk light to give a constant light source.
I take it you use non-glossy LCD screens? Glossy can cause eyestrain very easily – I can’t look at my mates Mac screen, which also seems to flicker.
Also don’t sit too close to your monitor.
I do eye exercises, like the Bates method, but more active, and I find this helps. It feels like you are stretching muscles – up and down movements at the left and right extremes seems to work best for me, plus some near/distance stuff.
See this book for Bates:
Opticians will object – but that is because, if it works for you, then you are not going to be buying any glasses from them.