I have a character in 1858 who needs to get eyeglasses. (He's based in London.) I've been able to find styles that were common, and the price at least in U.S. terms ($2.75), so if I can't find the British price, I can at least fudge it with a reasonable range of guesses. What I can't find is the process for getting them. Would the patient have had an exam and a prescription, or were they more or less just magnifying glasses that people tried on off the rack? If there was an exam, what would it consist of?