nowhere in the manga is it stated that it doesnt need eye contact.As much as i know it doesnt and if it does so why the hell its calling most powerful genjutsu and not Tsukuyomi?
the reason why it is a better genjutsu is because the victim of the genjutsu doesnt even realize that he/she is under influence of it.you can practically order someone to kill themselves and they will do it without realizing it was a genjutsu..instead they will do it because they believe they wish to do it.