Eye with refraction based on marmoset setup

Hi everyone, first time writing here, hope anyone can enlighten me. Recently I have being testing a way to simplify the eye mesh and be modular to use on realtime and high render. all worked out well on arnold and marmoset but somehow Unreal does not agree with me, at least not in a simple way.
The way this works is I have a mask texture that mask where I want the refraction to work, in this case with a 1.33 IOR. I was quite sure Unreal could do this as well as marmoset but it does not. I noticed the effect of the iris does not happen on the side view.
My question here is, is it possible to recreate the same setup as on marmoset and what could I try to achieve this.

For now all I have tried is to control the IOR with the camera distance, but is only works from the front view and even in closeup is not perfect.