As far as the English goes, I agree with Werner. When we talk about "prescription (eye)glasses" in English, we mean that a prescription is required for the lenses, though we don't typically say that. In actuality, lenses always come in frames, so when we say "glasses", we mean the frame and the lenses, which I understand as "Brille."
A: Nice glasses! (The person mostly likes the frames.)
C: Are those prescription sunglasses? (Meaning: was a prescription required for the lenses?)
D: Yeah, they cost a bundle, but I liked the frames.
E: Are those prescription glasses? (Meaning: was a prescription required for the lenses?)
F: No, these are just reading glasses I got at the drug store.
In A/B you could perhaps translate with Gestell, since what the person probably likes is the Gestell, but in C/D and E/F, I would find Kassengestell misleading. According to this thread, Kassenbrille would also be misleading. Siehe auch: Kassenbrille
I think what is meant from the English side is the "Sehhilfe" idea that Werner was getting at.