[ebook_fan]

I had the same problem some years ago.
I was a computer professional and for one year or so I used to work more then 10 hours a day using 14" crt standard monitor and, after that, I had to adjust the power of my glasses from "-6" to "-7".
After that I kept using the same crt monitor for an average of 4 hours a day without any further damage.

I am still aware of problems related to long working time using computer monitors so I tried to set my e-book reader devices to minimize eyes stress.

This is my choice:

1) Black white 100% light reflecting screen: I use an old black/white hpc (ericcson mc16) with 6" 640x240 pixel display; I switch off the backlight so screen works 100% with reflected light. The room lihgt has to be very good but eyes comfort is the same as if you were reading a paper book; maybe a little better because you can choice font type and dimension (I set it as big as possible) and line thickness. The result is ugly (the screen background colour is light grey/green - not really white) but you can use it for several hours and keep feeling comfortable.

2) Colour screen: I use a nokia 6630 phone with a 2" 208x186 colour screen. I set DARK BACKGROUND and WHITE TEXT to minimize the light emitted by the device; because of the high resolution I use small characters. I keep the same room light as if I were reading from paper. The comfort is good but not as the reflecting light screen.