^ Might have cause a bit of confusion with my above post, but the idea that Itachi is blind has become quite popular over the years due to the fact that the idea of seeing one of the most powerful characters in the manga leaping into battle behind a guide dog whilst wearing tinted glasses is hard to not laugh at.
And yes, there is a blind Itachi fanclub supporting this idea.
["You lost because you are weak." whispered Sasuke to the barely conscious for of his elder brother, "Why are you weak? Because you lack...." He kicked Itachi's slim white stick out of his limp fingers, "... eyesight."]
-Quote from a fanfic.