An eyeglass prescription is a written order provided by an eyewear prescriber, typically an optometrist or ophthalmologist, that contains all the necessary information for constructing and dispensing corrective lenses for a patient. It specifies the parameters required to address the patient's refractive error and provide clear vision.

Well the phoropter is the instrument that the optometrist uses on every patient every single day. It contains all the lenses that are used to calculate what someone's prescription might be. .

                      

This auxiliary dial is used to look for the astigmatism that might be in the prescription. And if we check for the coordination of the eyes and the muscle balances, and it will generally take about 10 minutes to do.