Many parents think that dilated pupils can harm their children’s eyesight, so they are concerned and even refuse to give their children dilated pupils. Many opticians do not perform dilated eye examinations, but why do doctors in hospitals recommend them? In particular, dilated pupils are required before excimer laser surgery. Dilated pupils require pupil dilation, which is only a superficial phenomenon. The essence of dilated pupils is to completely relax the ciliary muscle and loosen the adjustment to get the true refractive state of the eye. The eye is like an “auto-zoom” camera that can see both near and far through the contraction and relaxation of the ciliary muscle and the elasticity of the lens. If the pupil is not dilated during optometry, the adjustment of the ciliary muscle can cause the lens to become more convex and the refractive power to increase, which will not remove the adjustment of myopia, the so-called pseudomyopia. For this reason, adolescent optometry requires routine pupil dilatation to relax the ciliary muscle and completely paralyze it to avoid the effects of adjustment spasms and to ensure the authenticity and accuracy of the optometry. The importance of dilated pupils has been gradually recognized, and it is well known that adolescents under the age of 18 should have their pupils dilated for optometry. Many parents think that dilated pupils can harm their child’s vision, so they are concerned and even refuse to dilate their child’s pupils. In fact, dilated pupils are a temporary effect of the medication and only have a temporal effect on children. After the pupil is dilated, the child will experience temporary photophobia and difficulty seeing close to the eye, which will return after a period of time. The method of pupil dilatation is relatively simple and involves the loss of ciliary muscle regulation. Children under the age of 14 should have their pupils dilated slowly with atropine, while children over the age of 14 can have their pupils dilated quickly with atropine. Precautions for atropine pupil dilatation: 1% atropine ophthalmic ointment, twice daily for 7 days, with an optometric examination at the hospital on the 8th day. Fast pupil dilatation can be performed after 5 doses of the medicine and checking for dilated pupils, and the pupils can be restored 5-6 hours after the test. However, not all children can be examined with dilated pupils. For example, cases such as shallow anterior chamber and high intraocular pressure should be examined in detail before optometry, so dilated pupils need to be examined in a regular hospital. Adverse effects of atropine: (1) Atropine dilates the pupil and it is normal for patients to experience photophobia and difficulty seeing near; (2) Avoid bright light stimulation during pupil dilatation and wear a sun hat or sunglasses for outdoor activities; (3) During pupil dilatation, children should be watched carefully to avoid bruising due to blurred vision; (4) The pupil is dilated to relax the regulation of the ciliary muscle, so try not to use the eyes at close range during this period; (5) (5) Very few children with dilated pupils have symptoms such as flushing, thirst, fever, headache, nausea, vomiting, hallucinations, or excitement, which are considered to be adverse reactions to atropine and should be discontinued immediately or consult an ophthalmologist. Conditions in which dilated pupils are not appropriate: (1) Patients with suspected glaucoma, where examination reveals a shallow anterior chamber and intraocular pressure that is high or at the high limit of normal values. (2) Patients with glaucoma are contraindicated to apply dilated pupils, as this may lead to an increase in IOP; (3) People over 40 years of age generally do not have dilated pupils anymore due to weakened ciliary muscle regulation; (4) Severe lens and vitreous clouding and corneal leukoplakia make dilated pupils meaningless due to the difficulty in detecting shadow; (5) Severe posterior or anterior pupillary adhesions. If the pupil does not dilate normally even after the application of pupil-dilating medication, there is no need to dilate the pupil for optometry.