I'm sure it's been asked before but I wanna hear what some people think. We've obviously witnessed that Madara, Itachi, and Sasuke have gone blind from overuse of their MS. So how come Obito and Kakashi haven't lost their eyesight? I was thinking maybe the MS techs Tsukuyomi, Amaterasu and Susano'o are the only ones that degrade your eyes. Maybe the unique abilities like Kamui and Kotoamatsukami don't. What do you guys think?