Even though the Personal Vision Tracker works well when used properly, EyeQue cannot directly monitor the way a user takes a test. Therefore, we cannot guarantee the quality of the vision test results and the derived EyeGlass Numbers. Also, we do not guarantee that the EyeGlass Numbers are able to be used directly to order vision-corrective eyeglasses or other corrective eyewear. EyeQue does keep track of certain test metrics such as speed and consistency. EyeQue also rates the statistical quality of each set of results. Keep in mind that there is no absolute correct value for refractive errors. Even two optometrists will often come to different results when examining the same patient.