EyeWorks Eye generator is a procedural eye generation tool for use with Substance Designer, and Substance Painter. It comes with obj and fbx meshes, example scenes for Painter and Marmoset Toolbag3, Designer source files, and 6 eye materials already generated. Feature video here https://youtu.be/ooxqQaFKMQE

UPDATED: on 5/3/2019 and is fully compatible with Substance Designer version 2018.3.0 and Substance Painter 2019.1.0