Many myopic patients have had the experience of finding that they can’t see well enough to get a pair of glasses at the optician’s, resulting in myopia that is “getting deeper and deeper”. In fact, many myopic patients, especially adolescents, need to undergo dilated eye examinations at the time of their first eye examinations, and they must undergo dilated eye examinations. The purpose of the eye exam is to check the refractive state of the eye, whether there is refractive error, the type of refractive error and its degree. Based on the results of the eye exam, we can decide the prescription of glasses or other treatments. Therefore, the accuracy and reliability of optometry is directly related to the correction effect. Not only that, any disease of vision loss can be diagnosed clearly only when refractive error is excluded or corrected. Therefore, optometry is one of the most basic and important tests in the medical field. Why is it necessary to dilate the pupils of adolescents? Dilated optometry is the application of medication to paralyze the ciliary muscles of the eye, allowing the eye to rest in a quiet state for optometry. The advantage of dilated optometry is that it is accurate. Because of the strong adjustment ability of teenage eyes, inaccurate optometry results under the influence of adjustment often lead to overcorrection of myopia, i.e., the prescription is larger than the actual prescription. A pair of overcorrected glasses can be very damaging to the eyes of children and adolescents. The dilated eye exam eliminates the interference of adjustment, making the exam more objective and the prescription accurate. The myopia that occurs in adolescents is mostly caused by the bad habit of using the eyes at close distances, which is medically known as “regulatory myopia”; either it is based on the real axial myopia with the “pseudomyopia” component. The “pseudomyopia” component is either added to the true axial myopia. In short, the results of optometry under the influence of adjustment are very inaccurate, and if the phenomenon of “pseudomyopia” is also treated as true myopia to correct the prescription, it is very harmful, and dilated optometry can avoid this drawback.