Quote Originally Posted by Sidnne
I'm trying to think back to the chapter, without actually going back to look at it, but I seem to remember the blood running down from Sasuke's forehead and into his eye. Did that happen or am I imagining it? If that happened, that could explain it.

Those don't really look like whisker lines to me. They have a fleshy depth to them and appear to be more like wrinkles or scars.

That's right. I had forgotten all about that. We still never found out what Itachi said to Naruto. That's bound to raise a few questions now too.
Yes it was Itachi's blood that went into Sasuke's left eye and I'm pretty sure the fact that blood began flowing out of that same eye when Tobi activated his sharingan was no coincidence.

I don't think they look like whiskers either, they look like old scars, similar to those one would have if say their face was crushed by rocks but I'm not going there.

I don't know why you guys think something happened between Itachi and Naruto because as DB_Hunter stated we weren't shown anything to suggest that something did happen. He tried talking to Naruto and Naruto attacked him, then he asked him one question which Naruto was answering when Sasuke arrived and then Itachi left.