Two things I would like to point out
1- People always ask why is it that Kakashi or Obito hasn't gotten blind. Yes it's true MS makes you go blind eventually but it was never stated how fast you go blind. People think just because Sasuke went blind quickly that's how it works for all MS's. NO Itachi had his MS for years. He was gradually losing his eye sight but he never went blind. Why is that? Because he knows the toll Amaterasu takes on his eyes it's meant to be a last resort technique. And only used as such. Like an idiot Sasuke spammed it so of course he went blind quickly.
2- Kamui is a different type of technqiue from Amaterastu it's not as powerful so of course it wouldn't take as much as a huge blow to Obito's eyes. Kamui is meant to be used alot it would be idiotic for it to make the user go blind quickly . Basically what I'm saying is the more powerful the technique the more of a toll it takes on the users eyes.
People who state that Obito started this war cause he was friendzoned couldn't be more wrong. Yea I know Obito told Kakashi "It was because you let rin die" but I don't think he meant that genuinely, that was probably the start of his current path but it's not the soul reason why he is the way he is. He said it himself even when he was kid that he was gonna crush the ninja system. And when he was fighting Kakashi in the Kamui dimension he said "You think I started this whole war because of you(Kakashi) and rin alone? Don't flatter yourself" It's the ninja system itself that makes him sick. He had the same thought process as Nagato. If he wanted to see Rin so badly he just would've had Kabuto edo tensai her back to life.