It's true, it is exactly bad to your eyes if you often read digital books. To some certain degree, reading digital books is worse that reading books. Because you focus more with your eyes which will put stress on them thus your eyes will hurt, and you'd get a headache and the focus you put into it, will make it harder to focus in the future. I do not mean that you can not reading digital books, but you should pay attention to these tips. You had better change the brightness of your computer or telephone or something else less bright, which will be less harmful. Besides, you should not see the computer screen for long time, because this will make your eyes tired. It is recommend that you are supposed to take breaks in between while reading. Otherwise, you will have the dry eyes and redness. If you can not monitor yourself follow these tips above, I strongly advice you should read the paper books, which is much better than digital books.
Yes, reading digital books is bad for eyes. It may causes the problems of near-sightedness and astigmatism.
The display of your digital books has a great impact on your eyes, especially in the evening. That's why people's sight become worse if they use cellphones(such as surf the internet on cellphones) in the night. Also this may lead to astigmatism.
To protect your eyes, you'd better read real books in proper light and take a break when you feel your eyes are heavy. The light should not be too strong or too dim. Also, doing eye exercise and using eyes drops are helpful to protect your eyes.
According to the New York Times, there's no cut and dry answer. There is no evidence that reading on an e-book will harm your eyes. In fact, the lighting is very important. Devices with e-ink technology are best for use in sunlight or other well-lit environments. If you donâ€™t have proper lighting, these device can increase the chance of eyestrain. But e-readers like iPad, which have a backlit screen similar to a computer monitor, are easily viewed in a dark room, will become reflective in natural light or bright sunlight, resulting in glare that can cause eye fatigue. Actually, long time reading, no matter on a e-reader or traditional paper books, will cause sore, tired eyes. So take a break every 20 minutes to protect your eyes, and don't get too close to the screen.