The biggest thing about these eyes popping out is their context. If you want something to look really bright you put it next to a dark. So the rest of the composition being dark is really just a setup for all the little light spots.
Magnificent version of Nightmare Moon! And what i Like the most on this Version she doesn't "looks" evil a bit Mad (In a good way) but not evil. I hope one day we get a Comic from you about NMM and Celestia, i know there are a bunch of it out there but i would love to see it in your Style.