The EyeQue Personal Vision Tracker, VisionCheck and their associated applications have been tested and when used correctly, the EyeQue EyeGlass Numbers are comparable to those made with professionally used auto-refractors that are desk-sized and can cost more than $20,000. However, since EyeQue vision tests are self-administered, there may be errors if the test is not performed as directed. Based on our internal clincal study, most individuals with minimal accommodation experience results that are within 0.25 diopters of a professional auto-refractor reading when used properly. Those that accommodate heavily can have results that are up to 1.00 diopter difference from their last measurement. If you're unsure about your results, please contact customer support.