Board Thread:Theories and Speculation/@comment-3001903-20151205022433/@comment-5407586-20151205131529

There's also the fact that Madara was the one who trasplanted the eyes into Nagato. As the original wielder of the Rinnegan, he may have done something to lessen the burden of the eyes over Nagato's body. Something like a fūinjutsu to make sure Nagato would get used to the eyes before using them. On the other side, Obito had almost no time to get used to the Rinnegan he had trasplanted into his own left eye socket.