The eye on keyblades

[Ultima Fenrir]

What is the signficance of the blue/purple eye that appears on some keyblades like the oblivion and I think the way to dawn as well as MX's. Will this ever come into play at some point or is it just a design incorporated in some keyblades?

 

[carsonj]

I think it's supposed to be symbolism for something. I'm pretty sure that Hades made a thread about it.