Originally Posted by frahse
When you read paper, your eyes are probably moving more, as you move the pages. Try glancing up or around every few pages, or even on every page turn.
Great tip! I think that could very likely be the problem and moving your eyes a bit should help. With a kindle there is a tendency to stare straight ahead with less eye movement.
I have also read that taking brief breaks every 30 minutes or so and focusing on something in the distance for a brief time can help. Good luck. I hope you're able to figure it out.