Translucent surface refraction problem

I’ve been trying to get a good realistic glass material, and I think I’m making some progress, but I’ve run into a problem that I can’t seem to figure out how to fix. My surface only refracts the visible part of the scene, so if my refractive glass object is magnifying (minifying?) the scene enough that I ought to be able to see ‘offscreen’ information through part of the surface, it instead just abruptly switches to nonrefractive transparency.

globe1.png

Does anyone have a workaround? (I know this refraction isn’t quite right for a glass sphere regardless, but there isn’t really any point trying to tweak it until I figure out how to deal with the magnification issue.)