Eyeglass customers are allowed to buy glasses from any type of sources. The only restriction is that they must have a valid prescription from an eye doctor. A common situation is that a patient gets eye exam from a private doctor, after which his prescription is available. Then he can go to a local chain such as Lenscrafters to buy eyeglasses. In this case, the simplest way to check the received eyeglasses is to take it back to the private doctor. In most cases, the private doctor will be willing to point out any mistakes of the eyeglasses based on the prescription.
Some people receive eye exams at a retail chain such as Lenscrafters and also buy eyeglasses from it. This model is favored by all retail chains that they may offer free eye exams in order to attract customers. However, it is difficult for customers to check the accuracy of their eyeglasses. The reason is that the doctors at the same chain may be more lenient, otherwise the company has to do much business of remaking. In this case, customers can take their eyeglasses to another competitor for eyeglass inspection.