Often parents of children do not understand astigmatism, in fact, the reason is not complicated, an analogy will know. Most people weighing is wearing clothes on the scale, if wearing not much or very thin clothes, the weighing results have little impact, but, if wearing a cotton coat weighing, the error can be imagined, so, medically very accurate weight measurement, should be stripped naked to carry out, the reason why children’s optometry to be thoroughly dilated after the pupil, because children are too strong when looking at things, the results of the optometry have a greater Interference, so, in the process of optometry, it is necessary to find ways to block out this interference in order to come up with accurate results, which is equivalent to taking off the cotton coat and weighing. The reason why adult optometry does not require dilated pupils is that the influence of the adjustment power of adults is small, and not shielding it does not have a significant impact on the results of optometry, which is equivalent to wearing a thin T-shirt to weigh yourself, and the impact on the results is negligible. As for, what is “accommodation”? This is a term, non-ophthalmology professionals do not have to make it a waterfall, from the point of view of understanding, you just need to remember that it is an ability of the eye to see near objects, like the auto-focus function of a dumb camera.