I have managed to create a correct effect on one half of a sphere in that it seems to follow a reasonable distortion of the refraction map. I used a fresnel shader and adapted it to restrict it to refract, not reflecting, and adding my calculations for the refraction vector at each stage. I am having some trouble when the refraction is meant to turn back towards the outside of the sphere. Instead of a similar distortion to the other side, I am getting barely any distortion at all.

I will have to work through this tomorrow and see if there is perhaps something wrong with my calculations. I am also thinking of doing this with the shell structure. This might help me figure out the refractions as I can do it step by step.

My sandbox for the first model can be found here : Sandbox