If you use a small or old CRT as a computer monitor, get rid of it and get an LCD. As a CS major in college and working with computers after college, I watched my vision deteriorate while staring at cheap CRTs all day. For the last 4 years I have used exclusively either a laptop or a standalone LCD monitor and no longer have the intense eye muscle strain I used to experience. My vision improved dramatically.
I read up a lot on this subject on some aeromedical pages that are linked from the jet careers site. There are multivitamin supplements available at vitamin stores that contain all of the essential components for good eye health. There are a whole bunch of them, but the main ingredients. The main component in the supplement I have has Lutein, vitamin C, and E. I believe that the primary benefit of taking these supplements is to protect from long term oxidation damage and also improve night vision.