Surendipity,
I happen to prefer the white on black background myself, however was surprised when I did alittle checking on it....I thought this was interesting, and wanted to share it:
I searched the web under Eyestrain.
VIDEO DISPLAY TERMINAL CHARACTERISTICS
1. Good screen resolution is important- especially for extended work. Screens with more pixels generally provide better resolution.
2. Black characters on a white background is probably the best. However, other combinations can be comfortable so long as the brightness contrast between the characters and the background is high. It is best to avoid dark backgrounds.
3. The size of the text should be three times the size of the smallest text you can read. You can test this by viewing the screen from 3 times your usual working distance- you should still be able to read the text.
4. Monochrome displays usually have better resolution than color monitors. If the job does not require color, it is often best to use a monochrome monitor.
5. Although 60 Hertz is the most common refresh rate, higher refresh rates are preferred.
6. For color monitors, small dot pitches (less than 0.28mm) are desirable.
7. Adjust the screen brightness and contrast so that character definition and resolution is maximized.
8. The screen brightness should be adjusted to match the general background brightness of the room. This is much easier to do with light background screens.
I have found the biggest offender (for me anyway) to be the glare from other lighting sources located around my computer. Here at work I have about 15 computers in my room.....I work alone, so I turn off the lights and work pretty much in the dark except for everything being illuminated by the computer screens. There's no glare and my eyes never seem to tire from looking at the screens as they used to.
Hope this helps.
S

....(guess I could where shades at work)!