Here is a little eye material i use for my characters. It looks good med/close range. Customizable colors and reflectivity.
License: CC0 (why i had to use google drive)
EyeNodeShader.blend
https://drive.google.com/file/d/1awP5Kl98Dbh6PDNJ_nrpIcznyrGF99R6/view
EDIT: upbge 0.2.0 version with realtime cube
EyeNodeShader_RT_upbge020.blend
https://drive.google.com/file/d/1HNhn3foj6edNgNgPdhiOv8NQ2hs1pRHG/view