I've never had the luxury. Even if I try on their empty frames, and lean close enough to the mirror to get a general idea of what they look like, I have to take on faith (or ask someone else) that they look decent. By the time my heavy prescription is added, the refraction alters the way they look anyway.

Zenni has a feature whereby I can upload a photo, and get a reasonable facsimile of how a frame is going to fit, while wearing my current prescription to be able to actually focus on it. After 3 years of zenni, I went back to brick-and-mortar once, and faced extreme sticker shock.

Back to Zenni I went, and have been super happy with them since.