Board Thread:Naruto Discussions/@comment-24824148-20160724215526/@comment-5407586-20160725141457

Most likely Obito didn't show any blindness problems because he had Hashirama's cells embedded in his body. Seeing how the First's DNA allowed Danzō to use Kotoamatsukami more than once per day (when usually it'd take a decade to recharge the Mangekyō after each usage), it doesn't sound that far-fetched.