the eyes doesn't display in the viewport even if I put it in the material shading mode
Hmm - works perfectly here
I tried 2.81, 2.82, 2.83, and 2.90 (yes I know - I have waaaaayyyyy too many Blender versions, but when you're working on the bleeding edge you need them to see when the bugs you find have appeared)
It might be a bug with your system. Does it work when you switch to Material Preview?
Or is it just not working in all shading modes?