Does reading in the dark harm your vision? There is no evidence that reading in the dark will cause any long-term damage to the eyes or change to the physiology to the eye. It may cause some eyestrain or fatigue but there is no indication that this will increase myopia (nearsightedness) or harm your eyes.
Does reading on a tablet damage your eyes? Studies comparing various fonts, displays and pixel resolution found no difference in the effect on the eye between reading e-ink or a printed book. So if reading a printed book in dim light is okay, so i reading a Kindle. One difference though, is that devices like ipads, iphones and LCD monitors all emit a lot of light in the blue end of the spectrum (just think about that familiar blue glow you get from these screens). Blue light is known to scatter more and can cause increased eye fatigue. The good news is that lens companies are starting to produce coatings, like the Nikon SeeCoat Blue, that selectively filter out this blue light and reduce eye fatigue.
Michael Nelson OD, Waverley Eye Care