The Mrs is a licensed optician and she said this….. based upon your comment, I would say that they are taking a measurement, using a device called an auto refractor. The only problem with that is that there are people like myself that when you use an auto refractor, the prescription is completely opposite of what it really needs to be. I hope that they do several tests with that with you before determining your glasses prescription.”
Long winded comment from the Mrs.😍