Adolescents are the key period of physical development, and the development of the eye is synchronized with the body, and the development of the eye is also the process of refraction showing myopia development, so it is necessary to understand the development of the eye first in order to have a good prevention of adolescent myopia. 1. The development process of the eye is synchronized with the development of the body. At birth, the eye is small, a slightly flattened oval sphere, and its anterior and posterior diameters are only about 17 mm. With the rapid development of the body from birth to 3 years old, the eyeball also rapidly increases to a nearly orthogonal sphere with a diameter of 22mm; thereafter, until the age of 13, the eye does not grow in parallel with the body, it only grows 1mm in 10 years, which means that the diameter of the eyeball at the age of 13 is about 23mm, the eye has matured and the development of the eye has basically stopped growing at this point. Every 1mm growth in the eye axis is equivalent to a -3.0D increase in myopia. Of course, the eye is not such a simple organ, to achieve the function of a camera with automatic focus, there are lenses play an important role in it. 2, in the eye to play the role of the lens there are two main tissues, one is the cornea, that is, the surface of the black eye transparent membrane, convex; the other is the lens, biconvex, known as the camera “lens”. These two sets of lenses change their degree of convexity accordingly during the development of the eye to ensure that the light received by the eye is focused on the retina, the eye’s negative, to form a clear image. As the eye axis becomes longer, the corneal surface flattens and the lens pulls into a flattened shape, causing the focus to shift back and focus clearly on the retina to form 1.0 vision. 3. The ocular axis of the eye and the curvature of the cornea and lens work in tacit agreement with each other during the development of the eye to adjust the clarity of fundus imaging, and they are completely automatic and precise! But there is a limit to how much the cornea and lens can “neutralize or compensate” for myopia by changing the convexity by about -3.0 D. This is called “refractive matching or refractive compensation”. All current examinations of the eye are simply for central distance visual acuity. Because of the eye’s compensatory and neutralizing ability, myopic children under -3.0D often have a normal visual acuity of 1.0 during routine school physicals, and parents assume that normal visual acuity means that the eye is not myopic! In other words, to know whether a child’s eyes are normal, it is necessary to check the eye axis, corneal curvature, lens thickness and other parameters, which are medically known as “refractive factors”. That’s why people often complain, “The first-year vision check is normal, how to grow a couple of hundred degrees myopia in a semester!” This is the key to the problem that parents, opticians and general practitioners pay less attention to and do not detect in time! When children begin to read and learn, parents ask them to use the correct posture, use the eye and written distance to maintain at least 25 cm, and develop good habits. The table for reading and writing should not be too high. Make the vertical distance between the eye and the desk no less than 27 cm (the distance between the eye and the written determines the size of myopia and the time of continuous reading determines the speed of myopia development), preferably controlled at 27-33 cm.