Sniper Overlay Effect

Hello guys,

I have a small question.
Already looked and googled alot but don’t realy know what to search.

I have a Sniper Overlay, a realy simple one. like this:

Now my question is, how to make a Lense effect on the edge to the black circle?

Is this Possible with just a Material or how would u guys make it?
Im not that well into Materials.

Thanks and Greez,