Here is my not so simple EyeBall Shader for Eevee (didn’t try for Cycle). i’ve also included Text info and CC0 licence text inside the Blend file.
The Blend contain Only One Eyes mesh composed of two materials and a plane to preview the texture.
ABOUT THE BLEND:
Ready for Blender 2.81
-The eye_shader is not grouped for easy re-editing with node wrangler
-The left inputs red nodes are the editable ones
-there is a random on streaks and veins to variate the eyeball during the instance/copy
so you only have one shader for two eyes
-a shapekey for Pupil size
If you want to support my work and if you can, do not hesitate to drop some coins.
A Blender2.81 file with a procedural eye material node