1. Invert the colors whenever possible. Dark background, light text. Zenburn is a good color scheme for this, and you can find it for just about everything, from Vim and Emacs to Xmonad, to tons of other stuff.
2. LCD only. Not a problem these days, you don't see CRTs much anymore.
3. Don't hunch over your computer. Back straight, lean back, recline if necessary or get a standing desk, and increase the font size.
4. Look up frequently and practice refocusing on items of varying distances. Treat your eyes like muscles, work out your focusing ability.
FWIW, I looked into this a few months ago. I don't have any cites, but I found some reasonably persuasive articles that light-on-dark is best only for dimly-lit rooms. If you're in a bright office, dark-on-light is best. (And being in a brightly-lit room is probably best for mood and alertness anyway.)
The origins of dark-on-light as "readable" are old-school monochrome computer terminals, where the resolution was so low that if you used light-on-dark, you'd see all the individual pixels - light pixels lit up, dark ones didn't. We're past that now.
1. Invert the colors whenever possible. Dark background, light text. Zenburn is a good color scheme for this, and you can find it for just about everything, from Vim and Emacs to Xmonad, to tons of other stuff.
2. LCD only. Not a problem these days, you don't see CRTs much anymore.
3. Don't hunch over your computer. Back straight, lean back, recline if necessary or get a standing desk, and increase the font size.
4. Look up frequently and practice refocusing on items of varying distances. Treat your eyes like muscles, work out your focusing ability.
5. Stay hydrated.
6. Eat carrots.
7. Use F.lux or Redshift.
8. More if I think of it ...