Board Thread:Naruto Discussions/@comment-1018594-20160409062530/@comment-9782468-20160725150812

The first time MS-induced blindness was mentioned, was when Kakashi himself asked Itachi (or rather, Sasori's underling who was shapeshifted into Itachi) how bad his eye-sight was. Considering a few chapters later Kakashi himself was revealed to have MS, it stands to reason he would know about the deteriorating eye-sight because he himself was experiencing it. Kakashi's simply wasn't as bad because he hardly ever used MS.

-Omnibender

(I'll delete this if they come around and want to put it up themselves)