Board Thread:Versus Debates/@comment-26005711-20151018173351/@comment-26773508-20151101162225

Danzo's use of Koto without eye contact is sufficient ground to assume Koto works that way. There is no indication whatsoever in the manga about Danzo meeting Mifune before the Kage meeting, so there's little reason to believe in that scenario. Also, further proof comes from the fact that Hiruzen, Shisui and Itachi's original plan was to use Koto on the entire Uchiha clan during their clan meeting.

This plan seems incredibly risky and almost guaranteed for failure if we assume that Koto requires eye contact. Because while Shisui is locking his eye on, say, Itachi's dad, the other Uchiha would sooner or later notice that Shisui has his MS activated.

It doesn't matter much whether it was only a fleeting glance; there is a high probability that the more skillful Uchihas would notice Shisui's shenanigans shortly after Shisui starts using Koto on Uchihas individually. And that would lead to the failure of the mission, which would anger the Uchiha even more, thus defeating the purpose of the mission. So a much more reasonable assumption is that Shisui would secretly activate his MS while the other Uchihas are busy discussing the coup de'tat, thus avoiding suspicion. And that is possible only if Koto works within the user's field of vision without requiring direct eye contact.