Board Thread:Naruto Discussions/@comment-4271790-20140705012633/@comment-25072274-20140705043829

It seems that when one of Indra's descendants meet with Hagoromo, and he gives him half of his power, in this case, his eye, the eye has 6 tomoe. It doesn't seem to overshadow anything, it's just a way to obtain the dojutsu.