Is there any scientific backing to the claim that reading in dim light damages your eyes?
Related to: Does watching television damage the eyes?
No, there isn’t. This is a very old urban legend – nothing more:
Suboptimal lighting can create a sensation of having difficulty in focusing. It also decreases the rate of blinking and leads to discomfort from drying, particularly in conditions of voluntary squinting. The important counterpoint is that these effects do not persist.
No exactly like that, but the lack of outdoor/intense light exposure is an environmental risk factor in developing myopia. This factor is directly correlated with education, at least as currently practiced in East Asia, so a gene x environment interaction is probably the best description.
The mechanism how lack of exposure to intense light causes myopia is roughly (from the above sources): lack of intense/diurnal light decreases dopamine, which normally acts as an inhibitor to eye growth, which in turn leads to myopia.
So reading in low light is not bad for your eyes... unless this all you do. Also, all the sources I cited above are more recent than the myths paper cited in the accepted answer.