After dilating the pupil, the astigmatism may be smaller and usually changes little. Astigmatism is short for pupil dilation, a method that paralyzes the pupillary sphincter muscle in the iris, causing it to constrict, which results in a dilated pupil. After relaxation, this effect diminishes, and the astigmatism will be a little lower than it was before. Astigmatism is a symptom of defective visual function, and is caused by the fact that when parallel rays of light enter the eye, they form a focal point that is not in one place; this is due to irregularities in the curvature of the corneal or crystalline surfaces within the eye, and the eye becomes blurred. Dilating the pupil also causes the ciliary muscle lens to bulge, making the astigmatism smaller and seeing objects clearly. Therefore, the astigmatism may be smaller after dilation, and the patient will have photophobia after dilation, and it is recommended to wear sunglasses when going out. Usually pay attention to keep the habit of using eyes, do not long-term contact with electronic products.