Eye shader iris/cornea normal maps

Hi, I’ve been trying to learn how to create a setup like this where one normal map is used to push in for the iris and one bulges out for the cornea, but I just can’t find anywhere that shows how to set this up. I realise there are options like using separate geometry for inner and outer eye but I’m not specifically trying to create an eye shader; just learn how to implement this effect to try various things with it. I had a look at the eye in the content examples for 4.11 but it was too complicated for me to understand so I didn’t really learn anything from it. Any help would be greatly appreciated.