Recently, in outpatient clinics or telephone consultations, the most frequently asked questions by parents of children are: What is refractive error? What is refractive error and how does it affect the eyes? Today, I would like to give you a brief introduction to this knowledge: First, refractive error: people in the resting state of regulation (i.e., under the state of relaxation), the outside world, parallel light (both 5 meters away from the light) through the refractive system of the eye refractive, focusing on the fundus of the retina, the formation of clear images, known as orthopia; can not be focused on the retina, known as the non-orthopia eye, also known as refractive error. There are three major types of refractive errors: 1. Parallel light, after refraction by the refractive system, focuses on the retina before the eye – myopia; 2. Focuses on the retina after the eye – hyperopia; 3. Cannot focus on a point – astigmatism. -Astigmatism. Refractive error can cause low vision and is the direct or indirect cause of all types of amblyopia. Refractive characteristics of pediatric eyes: hyperopia is predominant, and the degree of hyperopia is higher than that of adults. In infants and preschool children, hyperopia accounts for more than 90%, and myopia is only about 2%. As age increases, hyperopia gradually decreases, and the degree of hyperopia gradually decreases. Mild hyperopia is a physiologic condition. Mild hyperopia is a physiologic condition, and most school-age children have mild hyperopia, while the proportion of myopia gradually increases after the age of 10. Most of the children are physiological mild hyperopia, so the visual acuity examination is normal, parents do not need to worry about this. Third, how to check the refractive state of children – pupil dilation optometry: because the children’s eye regulation, before and after the pupil dilation of the refractive state of the difference is large, so the children and teenagers must use ciliary muscle paralyzing agent (such as atropine, etc.) to dilate the pupil, it is possible to carry out accurate refractive examination, this method is also used to distinguish between true and false myopia. During growth and development, the refractive status of children and adolescents changes, as do visual function and diseases such as amblyopia and strabismus. Therefore, children and adolescents with refractive errors must be examined regularly. Preschool children should have an eye examination once every six months, and children aged 7 to 14 should have an eye examination once a year. Now that it is the summer vacation of children, we hope that parents will pay attention to their children’s eyes and bring their children to the hospital in time to prevent the occurrence of children’s eye diseases. Early detection and early treatment.