It is not necessary to review the pupil 21 days after dilation, if the use of short-acting fast-acting dilating drugs can be reviewed on the 2nd day, if the use of atropine and other long-acting dilating drugs, usually in 21 days. Commonly used dilating drugs include atropine (atropine ophthalmic gel or 1% atropine ophthalmic solution) and tropicamide eye drops. Tropicamide is a short-acting fast-acting dilating drug, which is usually used on the same day of the eye examination, and can be reviewed on the 2nd day. Atropine is a long-acting pupil dilator, the effect of the drug usually disappears after 21 days, after the drug expires, the pupil will return to normal size and contraction function, so the patient is usually retested on the 21st day. The main purpose of dilated optometry is to paralyze the ciliary muscle, and make objective measurements under the state of ciliary muscle relaxation, and arrive at a more accurate refractive error. If the retest is not performed within the prescribed time, the child may need to have the pupils dilated again. It is recommended that patients follow the doctor’s instructions for retesting after pupil dilation, and seek prompt medical attention when discomfort occurs.