Glasses are a total racket. Purchasing your glasses online is many, many times cheaper than going to Lenscrafters or basically any other brick & mortar store in the US. I've been buying online for years and they're every bit as good as usual ones. You do need your pupillary distance, but you either measure this yourself with the help of a friend, or ask your optometrist. If they refuse or tell you how evil buying glasses online is, get a new optometrist.
The best sites I'm aware of are:
http://www.zennioptical.com/ (what I use)
https://www.goggles4u.com/
https://www.39dollarglasses.com/