@OP: I had the same experience as you. I also have the Sony PRS-600.
From the research I've done, I don't think computer screens can damage your eyes. You can get eye strain from looking in once place for too long, but it doesn't do permanent damage. But, I'm no expert on all that. I also look at a screen for about 12 hours per day, and I don't have any problems with my eyes. Wrists, neck, and back are not quite as fortunate for me though.
