This eye setup started as an experiment to see if I could get a performant, flexible, and appealing eye working with only a standard sphere and some math, instead of the layered approach using either geometry or multiple passes of shading.
I displace the cornea, calculate approximate corneal bulge normals, place the iris surface at an approximate location via distortion, and provide parameters to control the visual properties.
I wanted this to be flexible enough to use across many types of characters. It is still a work in progress and will continue to be developed.