Often encountered in the ophthalmology clinic, because the child’s vision is not good, come to the parents of children, the first sentence is: “doctor, check the eyes without dilation, right?” This highlights the misconceptions and prejudices in society about dilated optometry for children. The essence of dilated optometry is to relax the fatigue of the eye muscles due to prolonged overstress, so as to obtain the true refractive state of the eyes. Pupil dilation is the application of drugs to completely paralyze the ciliary muscle of the eye, losing the regulation of the condition of optometry. This is mainly because the children’s eyes are strong, if the pupil is not dilated, the ciliary muscle regulation can make the lens convex, refractive power increased, can not be adjusted myopia that is the so-called pseudomyopia component is removed, and affect the accuracy of the results. So children patients, dilated optometry is very necessary. There is a difference between fast and slow pupil dilation; children under 12 years old should use slow dilation for accurate results. Of course, depending on the specific circumstances, the doctor will choose the appropriate way to choose. Dilated pupils are not dangerous for children, except when they have difficulty in seeing and are afraid of light (fast dilation lasts 5-6 hours, slow dilation lasts for three weeks), and are used in moderation.