Christoph Werner writes:
CW Eye is a procedural material shader tree for Blender.
You can create countless eye variations just by changing some values in the shader. Starting at „simple“ human eyes you can create eyes for aliens, zombies or whatever you imagine. A lot of options are supported, like veins intensity, iris size or multiple eye patterns and colors.
Five cool eye presets are included in this package. Feel free to use them as a starting point for your own variations!
Your results can be baked optionally into textures by using Blenders internal bake system.
Drop me a line if you have questions.