Miss Nancy - in bagginsbill's shader and that image the sphere casts a shadow because it's not transparent and it's not set to not cast shadows or be invisible to raytracing.  in all versions of Poser refraction does not  actually allow light to go through the object.  to handle that, it would have to have caustics.  it doesn't.  you're confusing what the surface of the object does and what that material does to other surfaces.

this is why bagginsbill made his eye prop.  it needs a separate lens group so that it (and not the rest of the eye) can have shadows turned off.  if you look up his discussions on the topic, you'll see that this is required to stop the iris from being shaded in Poser.  it is not required in any renderer that doesn't support caustics.  the same way reflections aren't included in IDL calculations, refraction is not included in shadows, AO, or IDL.

if you look up his information on glass, you'll also see his script for glass panes using his TrueFresnel equations (he hasn't been using that EdgeBlend trick in a while), reflection and transparency.  and why he suggests using that rather than refraction for glass that has negligible net refraction.  he's written about the issue and the transparent window glass  for years.

from the BBEye page (http://sites.google.com/site/bagginsbill/free-stuff/bbeye)
"The eye is in two parts. The cover part must not have shadows enabled. It requires ray-tracing as it uses reflection and refraction."

that said, i discovered this before reading his posts about it when i tried to light a room through glass windows and ended up with no directional light coming through.  i asked him about it, and he explained.

as for the discussion of refraction and dark matter, you're just not making a lot of sense.  it has nothing to do with thickness (which is actually a problem with Poser refraction).  it's simply a limitation of Poser's renderer.