The difference in each optometry test may be caused by the measurer’s error, machine error and the measured person’s error, etc. The difference is generally small and acceptable. 1. Measurer’s error: There are some differences in the operation of each doctor and optometrist, which may cause some errors in the results of the optometry, and may cause each optometry to be different. 2. Machine error: each machine measurement results can not be completely consistent, but with the increasingly sophisticated medical equipment, the error is often smaller, but generally can not guarantee that each optometry results are exactly the same. If it is within the margin of error, it is generally acceptable. 3. Measured by the error: the refractive state of the human eye is not very stable, the eye to see different distances from the target requires a different amount of adjustment, so the performance of the refraction is different, the general adjustment is easier, but in the fatigue is an error, so there will be a different optometry. It is recommended that patients with refractive error consult a doctor in a timely manner, under the guidance of the doctor to carry out the correct optometry, optometry results of abnormal patients consult a doctor in a timely manner, to assess the condition of the patient, and comply with the doctor’s instructions for treatment.