So Obito has been using Kamui since he was about 13 or 14. [dont know the exact age] He uses it constantly since then and shows no sign of going blind. Im sure he does not have EMS so i cant see why he nor kakashi has gone blind. Sasuke just got his MS not too long ago and when he used amatersu spammage he showed signs of going blind. now this leads me to believe Kamui uses less strain so takes longer to make you go blind, or kamui has no effect on eye sight at all. either way it is unknown i guess. Also why does no other uchiha have kamui? what theories do you have on why Kamui is so exclusive to these two ninjas and what do you think about Obito not going blind after so much usage of the jutsu?