1. Internal factors (1) Genetic quality: Myopia has a certain genetic predisposition, which has been recognized, especially for high myopia. However, for general myopia, this tendency is not so obvious. For those with genetic factors, the age of disease is early, mostly above 6.00d. However, there are also people with high myopia who have no family history. High myopia is an autosomal recessive inheritance, while general myopia is a multifactorial inheritance disease. (2) Developmental factors: Infants are farsighted because their eyes are small, but as they grow older, the eye axis gradually lengthens until puberty when it develops normally. If the development is excessive, myopia will be formed, which is called simple myopia and starts in the school age. It is usually below 6.00 d. The development stops at the age of 20. This is called high myopia or progressive myopia or pathological myopia. This type of myopia can develop and degenerate in later life, so vision can gradually diminish, and glasses cannot correct vision. Rarely is myopia present at birth, but very few are congenital. 2. External causes Common causes of myopia also include environmental factors. People who work in writing or other close work have more myopia, and there are more myopia among teenage students, and their prevalence rises significantly from the fifth or sixth grade. This phenomenon shows that the occurrence and development of myopia is very closely related to close work. In particular, the eye of adolescents is in the stage of growth and development, with strong adjustment ability and large extension of the spherical wall. The adjustment and collection during close work such as reading and mailroom make the extraocular muscles (mainly the internal rectus muscle) exert certain pressure on the eye, and the intraocular pressure rises accordingly. The ciliary muscle and extraocular muscles are often under high tension and the excessive regulation can cause spasm of the ciliary muscle, resulting in a temporary loss of vision. However, after rest or the use of ciliary muscle erosion agents, vision may improve in full recovery. Therefore, some people call this myopia functional myopia or pseudomyopia. However, the scleral tissue is gradually extended by the long-term mechanical compression of the extraocular muscles, the eye axis is elongated, and the myopia becomes deeper and deeper and can no longer be relieved by atropine, etc. The lack of attention to visual hygiene, especially during adolescence, is a direct cause of myopia. The lack of attention to general health contributes even more to the development of myopia.