I'm using Eevee. I followed a tutorial to create an eye. It looks great from the front:
Its side shows some weird circles (I know it might be due to the transparent lens but I don't know how to solve):
Here's the tutorial that I followed: https://www.youtube.com/watch?v=gfEyhPXsOCM
I wish if there's an easy solution or another tutorial that gives a good look without affecting the performance.