Render objects when camera views through another object

Hey All,

This one is a bit hard to describe so I am going to draw what I am looking for.

I want to only render the objects that are viewed through the object like a lens.

I want to have the objects viewed at full depth and color but only through the front of the lens.

How can I accomplish something like this? Is it a post-process effect?

My build target is Virtual Reality.