Holy shit, Do I have a new theory, holy fuck!!!
the Eye has six dots around it, most Omnics have have up to Nine dots on their forehead and some cultures believe there third Eye lies in the center of their Forehead. I'm speculating but what if the Eye is the symbol of who (or what) created the Omnics (or at least gave them sentience). It's also possible that some Omnics have a vague memory of that Symbol, which would explain why it would become the focus of their religion (being the Symbol of their creator and all). Holy shit Sombra Stumbled upon some shit. Just to be clear, I'm not saying all Omnics are evil, but whoever created them probably wouldn't that information to get out.

"Gaze into the Iris"