Why do children need to have their pupils dilated for optometry? Depending on the refraction, the pupil will be reviewed the next day or 3 weeks later to determine the number of lenses to wear. The purpose of the pupil dilatation is to paralyze the ciliary muscle, thus paralyzing the adjustment effect, so that the optometry can be correct and conducive to the treatment of amblyopia. Some parents feel that it is too much trouble and too long, and often ask not to dilate the pupil. However, the eyes of children under 12 years of age are highly regulated, so if the pupils are not dilated with a diluent, the error in the prescription will be large.