There is a difference between postdilution and retest vision; postdilution vision may be relatively low and retest vision relatively high. The number of diopters is often not the same between the post-dilution and review tests. Dilated eye exams are an objective measurement of the refractive error when the ciliary muscles are relaxed, whereas follow-up eye exams are performed when the pupils return to their normal size and contraction. Therefore, the refractive error may be relatively low for a dilated eye exam and relatively high for a review eye exam. Visual acuity examination may include vision chart screening, visual screening, dilated pupil optometry and biological measurements of the eye. Dilated pupil optometry is based on visual screening, and then the corresponding dilated pupil optometry is performed to determine the refractive status of both eyes. There is usually a difference between the visual acuity after dilation and the visual acuity after review. Patients should pay attention to maintaining good eye habits, and if abnormal visual acuity is found in the optometry examination, the cause should be identified under the guidance of the doctor and corresponding corrective measures should be taken.