How do EyeGlass Numbers differ from my eye doctor's prescription?

By definition, an eyeglass prescription is a certified order written by an optometrist or opthalmologist.  Optometrists typically use a tool called a Phoropter to test individual lenses on each eye during an exam.  If you have myopia, hyperopia or astigmatism your doctor will use a phoropter to help write your prescription.  The important point in this is that the prescription itself is a certification more than a method used during an exam.  EyeGlass numbers are created by the EyeQue Personal Vision Tracker.  They are not certified by an optometrist, although they do measure refractive error.