Here’s my head with eyes
Here’s the node graph for the eyes, it got a bit complicated…
I generated the blood vessels from a voronoi texture and used a colour ramp. I detected which parts of the eye were white by adding a UV map where all the points were in the white of the eye texture (before I realised it was just ffffff ) and comparing the value of the colour with the known white colour, the main Image texture node I switched to clip and then raised the alpha value (0 when clipped 1 when not) to the power of the difference between the colour and the white colour (close to 0 when nearly white and 0 when exactly white), then use that value to mix between the iris material and the blood vessels/white material.
The simpler bit is just SSS for the white and irisand a fresnel/glossy mix at the end. I had to add a diffuse shader to the SSS of the eye white because it was too dark on its own.
