Reminder, if you're in the US, the FTC says your eye doctor must give you your prescription after your exam. If a doctor refuses to do so, they can face legal action and penalties. https://www.consumer.ftc.gov/blog/2016/05/buying-prescriptio... That said, I don't think the FTC stipulates what information must appear on the prescription. Many docs leave off your PD (pupillary distance), which is a necessary measuremen…
They’ll give you your prescription and literally wouldn’t sell me glasses even if I wanted them, since I wasn’t a store member. I did have to measure my own IPD though, which I did with a ruler and a mirror.
EDIT: another reply notes that they did get their IPD at Costco, so this might vary by location. As they mentioned, the optometrists are independent.