A photopter is what optometrists use when they check the vision in your eyes. It is the metal instrument that you look through when going through an eye examination.
A phoropter is the big machine opometrists use to figure out which correction you need in your glasses. Your son is unlikely to locate one for public use.
A phoropter is an instrument that is used by eye care professionals during an eye examination. It is used to determine a person's eyeglass prescription.
