SPECULATION Dark Side Eyes

I don't have a good answer to the main question, but Dooku rarely had them, if I recall correctly. Yet as far as I'm aware, he was cemented in the Dark Side. So they may not be a necessary feature. But I'm not sure.

 

Awesome thread man!
1) Most apperances of these eyes are in extreme emotion, hate, anger and revenge.
2) From all notes I have read they really shouldn't be, but say in the case of Maul etc, it could be due to his species or the fact he was raised to harbour the darkness so they might be his only emotions.
3) To be honest I think there is more to it, this scene in general. I think first off, he hasn't accepted the darkness fully, he's still toying with the light and you know people theorize Kylo is doing this to get close enough to kill snoke. But that aside, I truly believe Han helped Kylo kill him, rather than an emotional murder!
4) Like said before, I don't think it's constant and it might not affect everyone, eg, Dooku, he is arguably the most controled when it comes to emotions and force balance, hence why we don't see this from him, even at the momet Anakin kills him.

So yeah this is my take on it man, hope it helps a little bit

 

The thing that has always puzzled me is why didn't Dooku get Dark Side eyes. And before anyone comes with the whole ''He wasn't a true Sith'' argument, I remind you that in order to be able to use it, a person must have fully embraced the Dark Side. That, and the fact that knowing how sly Sheev was, he would not have trusted Dooku with said knowledge if he wasn't 100% sure that he had fully become a Sith.

 

1/2.) they appear only after a truly horrible act has happened (sort of like a horcrux) which is why Dooku never had those eyes since, as far as we know, didnt kill a bunch of defenseless kids.

3.) That makes me think that, what if, Kylo Ren is a secret plant in the first order.

4.) That might be because he's blind?