The refraction of the human eye is closely related to the length of the eye axis. At birth, the length of the eye axis is about 17.6 mm, which is generally characterized by high hyperopia. By the age of about 3 weeks, with the development of the eye, the eye axis grows rapidly and the degree of hyperopia decreases significantly. 3-7 years old, along with the further growth of the eye axis, the refraction will develop from hyperopia to orthopia. 7 years old, the development of the eye is basically perfect, and the normal eye axis is generally 23.5-24mm. Refractive errors are divided into three categories: hyperopia, myopia and astigmatism, and their change patterns are as follows: 1. Evolution of hyperopia Before 3 years old, within +3D, normal. From 3 to 7 years old, the degree of hyperopia gradually decreases. After 8 years old, the farsightedness of adolescents is basically stable. 2. The evolution of myopia 7-18 years old, closely related to physical development, is a critical period for myopia control. After the age of 18, the growth slows down significantly and is basically stable if there is no excessive eye use. 3.Evolution of astigmatism At birth, astigmatism is high. After 6 months, astigmatism begins to decrease, and by age 7 astigmatism gradually decreases. After 8 years of age, the overall change in astigmatism is not significant. When abnormal refractive status occurs in adolescents, they should be examined at the hospital as early as possible and corrected and treated accordingly according to their individual conditions.