The difference between dilated and non-dilated pupils is that the results of an eye examination after dilation are more accurate, while the results of an examination without dilation are not as accurate, and a refractive examination and funduscopic examination can be performed after dilation. Refractive examination is optometry, because many teenagers suffer from myopia are pseudomyopia, this is a kind of myopia caused by the ciliary muscle is not relaxed, so you need to dilate the pupil to paralyze the ciliary muscle, and then refractive examination, so as to get the myopia is more accurate, without dilating the pupil for refractive examination, the myopia is often on the high side. The difference between dilated and non-dilated pupils also lies in the fact that, before the fundus examination, the pupils should be dilated in order to fully observe the fundus, and if the pupils are not dilated, the field of vision of the fundus is limited; dilation of the pupils requires the use of medication such as tropicamide, aftermatropin, atropine, etc., and the pupils do not need to be dilated without the use of medication. If you need to dilate the pupil for related examinations, please follow the doctor’s instructions.