Eye Shader in unity3d. Vertical pupils. or Custom pupils.

As I see in manual there is an eye built in shader in unity3d.
https://docs.unity3d.com/Packages/c...s.high-definition@10.2/manual/eye-shader.html
Can I make vertical pupil with it, and how to do this ?
(or generally custom pupils)

 

So after almost one year I'm in the same spot, what I tried is to edit the eye mesh vertices and squeeze pupil ventricles a little.

Unfortunately it looks like the eye shader is not using this vertices UVs to render eye, the shape of eye mesh changed but eye texture is projected onto it without any changes.