Quote Originally Posted by Buffalobiian
He hasn't displayed signs of "weak" sight, but the fact that he admits he knows the diminishing sight as a side effect means he is already suffering from a "noticeable loss of sight".
Not really, it might very well just mean he also found that Uchiha shrine Itachi told Sasuke about.

I'm sure his MS didn't just pop out of nowhere, there had to be something to activate and since battle is out of the question study is probably it