It is much healthier and less weary on the eyes to use the high contrast feature in Windows from (XP up, I believe), by pressing shift+alt+print screen (and space bar.)

One can spend much more time reading on the screen.

Another feature I use a lot is zooming with ctrl++ in FoxIt or Adobe PDF reader, and ctrl+up on the mouse wheel in Mozilla Firefox(and Chrome), some web designers tend to use very small fonts where they shouldn't(let alone blogs, which are designed to be thinned out to leave space for advertising at the sidebars.)

If that doesn't work, I use the excellent gratis ZoomIt tool, to zoom in sections that are otherwise not available through the aforementioned tools.

I tend to distance myself from the computer monitors at least one meter to avoid eye strain and the low but permanent radiation.

I remember when I played first person shooters I suffered from nausea. Spyro the Dragon and games that require a lot of manual camera manipulation also causes the same effect.

I blogged about how to avoid eye strain with simple exercises every 2 hours.

There seems to be a lot to do in life, and maintaining pauses without diminishing productivity is achievable by, for example, having a snack or running in the neighbourhood where one is constrained to focus farther away.

I generally just use the default themes. I might change the wallpaper, and on Windows 7 I'll pick the record player as my user account pic, but that's about the maximum of what I do. In programs where themes are on offer it's the same, with the exception of Office 2013 where I must switch to dark grey in order to maintain my sanity (it's too difficult for me to differentiate between the various on-screen elements otherwise).

Main reason why is that I spend my working life hopping between so many different PCs and servers that if I needed to spend half an hour or whatever getting things set up before I could use it, I'd get nothing else done. In those kind of circuumstances you tend to get used to the default themes pretty quick.