Hello fellow Blackbusher :thumb:
I carry my old prescription glasses as my spare pair, since my prescription didn't change much last time it was updated. I've got prescription sunglasses too, but rarely use them, just have them wedged into the case with my spares. Frankly I can see alright without any of them, but rules are rules and I find going from prescription glasses to non-prescription does take a few mins to adapt to, so prefer to keep it constant between sunnies and non-sunnies.
Thing that bugged me was frame style - I used to favour the thick framed 'I work in the media doncha know' type of glasses but found them really annoying to wear with a headset - all sorts of problems with that. Changed to some glasses with much thinner frames and everything's gravy now.