well if he used izanagi he should lose one eye , but after the fight with konan he has his eyes . eternal mangekyo is meant to last . sure, the wounds inflicted on him by hashirama must have been great, but they don't seem to delay him at all.
he must have something else up his sleeve . another thing that has been bothering me is the fact that his eyes seem to be active constantly .we know that a non uchiha transplanted with the sharingan has the eye active , but why madara . anyway madara mentioned that izanagi is a jutsu that requires a mix of senju and uchiha blood ,and if what he said about his fight with hashirama is true (that he fought because he wanted his blood ) then he reached a level beyond the level he claims to be right now. he is the only person that mastered the eternal mangekyo and there must be something about this eye that we don't know and soon find out .
