Yes, it is bad for your eyes. Because the screen is so near and small, the ray of light will come into your eyes directly. If you look at it in the night, your eyes may get tired easily, thus you may get short sighted. if you use phone for a long period of time in dark night, it not only can cause the short sighted, but also affect body health.
Well, it seems that you care a lot about your eyes and eye health. So, as to your question, the answer is absolutely definite, it is bad for your eyes, hard.
Because as you know, in dark environment, our eyes will be completely attracted to the screen of the cell phone, which would have great impact on our eyes. So, I recommend that you play less cell phone in the dark. Hope you find this useful.
Yes, using the phone in the dark is bad for the eyes because of the too near distance from the light resource and the strong stimulation for the eye nerves. If you do this often, your eyes may get short sighted. Or you may get other eye problems. Thus you'd better not do this.