Some people need to have their eyesight dilated when they have their eyesight checked, including: 1. The first time you go to an optometrist, you must have your eyes dilated; 2. If you have hyperopia or astigmatism, you should continue to have your eyes dilated when you have your eyesight checked again. Because the human eye needs to use the regulating force when looking at the near, the regulating force relies on the contraction of the ciliary muscle, and if you look at the near for a long time, the contraction of the junctional ciliary muscle will be too long to produce spasm, so it cannot relax by itself. In this case, myopia or the point of entry of the human eye is close to the eye, which is not the normal vision of the human eye, but myopia or a special case by insertion optometry or bare eye vision examination. In this case, the spastic muscle must be completely relaxed by dilating the pupil, and only after relaxation is the true prescription of the human eye.