I happened to noticed one day that in other anime the Sharingan "3 dots symbol" or whatever you want to call it appered. I happened to think that it was an original creation, or something similar, but I saw it in yugioh and one piece, which makes me think that maybe there is a cultural meaning or something. Not that I was thinking too much into it, just that after I saw it 2 other places, made me think that it meant something for 2 other mangaka to use the same thing
images:
sorry for the bad quality on the first picture, I'm not sure what one piece character it is, i got that little figure in a japanese candy ^_^;