HDRP refraction on material using opacity

I'm working on a material for the tearline mesh surrounding character eyes. This catches the light and suggest water around the eye. Turning on refraction enhances the effect, blurring the edges and making the tearline more realistic. However, refraction doesn't seem to work with opacity. The material should fade out from the centre line, reaching 0% opacity before the mesh edges marked below. As the image shows, the entire mesh is visible so there's a noticeable line.

Should HDRP refraction support opacity, or will it always show the entire mesh regardless of the opacity channel in the material?

Any help is much appreciated.

 

Is the eye itself opaque?

 

Yes it is.

 

Is this a limitation of HDRP refraction? Is it applied to the whole mesh regardless of material opacity?

 

To test things I created a simple unlit shader which uses an alpha texture and distortion. The distortion seems to ignore the alpha. Is this deliberate?