Many parents are reluctant to have their eyes examined because they feel that the dilated eye exam takes a long time and that their eyes are uncomfortable afterwards. So, why must adolescents have dilated eye exams? What is optometry? Optometry is the determination of the refractive state of the eyes, the presence or absence of refractive error, the type of refractive error (including myopia, hyperopia, astigmatism) and its degree. Based on the results of the optometry, we will decide whether we need glasses and the prescription of glasses, so it is very important that the optometry is accurate. Not only that, any disease of vision loss can be diagnosed clearly only if refractive error is excluded or corrected. Therefore, optometry is an important examination tool in the field of ophthalmology. Optometry methods: Subjective optometry (e.g., insert method), in which lenses of different degrees are placed in front of the patient’s eyes to measure visual acuity, relying on the patient’s judgment to select the most appropriate spectacle lenses. This method has poor reliability and is not suitable for children with poor expression and comprehension. This method is commonly used in general optical stores. The objective optometry method is not influenced by subjective factors, and its reliability and accuracy are good. The most common and accurate method is the retinoscopy method, which is usually used in hospitals. This is because the regulation of children and adolescents’ eyes is very strong, and they usually have a heavy study load, spend a long time reading and writing, and watch TV and play computer games excessively, so their regulation is often in spasm, and they cannot relax completely even in normal times. Therefore, the myopia that occurs in adolescents is either pseudomyopia caused by bad habits of using eyes at close distances; or pseudomyopia is mixed in with the real myopia. In short, the results of optometry without dilated pupils under the influence of accommodation are often inaccurate, resulting in a higher prescription than the actual lenses that should be worn. If pseudomyopia is corrected with prescription lenses, it can be very harmful, and dilated optometry can avoid this drawback. For patients with pseudomyopia, dilated pupils are the best treatment for pseudomyopia: they allow the child’s ciliary muscles to relax completely and force the eyes to rest. Adolescents and children with hyperopia need to use the eye’s regulation to see both near and far. Therefore, in order to see objects at any distance from the outside world, the farsighted eye has to contract the ciliary muscle to enhance refractive power. If the ciliary muscle is not paralyzed, the accommodation may mask some of the hyperopia and make it impossible to detect. The younger the patient, the stronger the accommodation, and the higher the hidden prescription. It is not possible to detect the full extent of hyperopia without dilating the pupil. In some cases, children with mild hyperopia are misdiagnosed as myopic because they are not dilated, and are given the wrong glasses, leading to adverse consequences. Therefore, it is imperative that adolescents with hyperopia have their pupils dilated for optometry. In eyes with astigmatism, the degree and position of the astigmatic axis can be checked more accurately after pupil dilatation. Generally speaking, adults with low to moderate myopia and those who wear glasses regularly and whose prescription does not change significantly can get the accurate prescription for the best vision using the direct trial method or the computerized examination method. However, for adults with hyperopia, high myopia, high astigmatism and significant changes in prescription, it is often difficult to determine the best prescription because it is not easy to obtain the best visual acuity by trial lenses. For patients with refractive error combined with strabismus, the close relationship between adjustment and strabismus shows that generally farsighted eyes are prone to internal strabismus and myopic eyes are prone to exotropia. These patients wear glasses not only to improve their visual acuity, but also to treat strabismus by wearing glasses. All of this is subject to finding out the exact amount of refractive error. This is why it is important to dilate the pupils of these patients. The usual dilating medications we use are: 1. tropicamide, which has a duration of action of about six hours; also known as rapid pupil dilatation. 2. 2. Atropine, which has a duration of action of about three weeks. Atropine is usually used for pupils under 12 years of age, especially in patients with first-time myopia, and in patients with hyperopia, especially those with internal strabismus. The specific type of pupil dilator to be used and the method of use should be done under medical supervision. Of course, not all patients can have their pupils dilated, and this needs to be clarified by the ophthalmologist. The last point to emphasize is that objective dilated eye examinations do not result in the prescription of glasses for the same number of prescriptions. In the case of dilated pupils, the refractive state is not physiological, and when normal conditions are restored, the prescription may change slightly. Therefore, after the dilated eye exam, the measured refractive error must be verified, adjusted and tried on by the subjective trial method. In other words, a combination of subjective and objective methods is used. The prescription is made by an experienced doctor based on the patient’s age, prescription size, nature of the refractive error, and the presence of strabismus. Therefore, it is best to go to a hospital for a scientific medical optometry examination.