Board Thread:Theories and Speculation/@comment-734582-20150712141917/@comment-26911440-20151207143534

I know.

That isn't what I am meaning, what I am meaning is that doesn't it seem like the Mangenkyo taps into one or two aspects of Kaguya's own ability - which by pure coincidence happens to be their ancestral- and for using that ability, it means blindness.

Kakashi even said that her ability to create new dimensions and re-write happens like how a genjutsu does, and the only ability known to do that makes the user blind, regardless if he has the EMS. With the only way to recover the eyes being to evolve into the Rinnegan.