According to relevant data, the number of myopia in China has reached 400 million, ranking first in the world. The incidence of myopia has reached 1.5 times the world average, and the incidence of myopia among teenagers is as high as 50 to 60 percent. So what are the reasons for such a high incidence of myopia among teenagers? Experts at Tianjin Medical University Eye Hospital explain in detail the causes of myopia. Six common causes of myopia 1, the eye distance is too close According to relevant information, adolescent myopia to long-term eye distance is too close to cause the most common. The distance between the book and the eye is 7-10 cm, but if you read and write at this distance, you will have abnormal tension in your eyes, which can lead to refractive (regulatory) myopia, the so-called pseudomyopia. If you over-regulate for a long time, the ciliary muscle cannot stretch flexibly, and the convergence is strengthened due to over-regulation, so that the extraocular muscle exerts pressure on the eye, the intraocular pressure increases, the intraocular tissue is congested, and the youth eye tissue is delicate, the wall of the eye is gradually extended by pressure, the front and back axis of the eye becomes longer than the normal value, and axial myopia is formed, so called true myopia. The normal reading distance should be 30-35 cm. 2, the eye time is too long Some adolescents read and write to do homework, watch TV and so on for 3-4 hours without rest, or even to sleep and rest late at night, which not only affects health, but also makes the eyes overburdened, the muscles inside and outside the eyes for a long time in a state of tension and not rest, over time, when looking at the distance, the eye muscles can not relax and spasm state, so look at the distance to feel blurred and the formation of Myopia. Some students’ eyesight declines significantly after a summer vacation for this reason. It is generally advocated that continuous reading and writing or watching TV for 40-50 minutes should be rested for a moment or look into the distance for a while. 3, lighting too strong or too weak If the light is too strong, such as sunlight shining on the written, will cause strong reflection, stimulate the eyes, so that eye discomfort, it is difficult to see the font, on the contrary, the light is too weak, the written lighting is not enough, the eyes can not clearly see the font, the head will be forward, close to the book, the above two cases can be easy eye fatigue, eye regulation or spasm and the formation of myopia. 4, in the car or walking when reading books Today’s teenagers make the most of their time, reading books while walking or reading books in the walking carriage, which is very bad for the eyes. Because the carriage is vibrating, the body is shaking, the eyes and the book distance can not be fixed, coupled with poor lighting conditions, increasing the burden on the eyes, often so it may cause myopia. 5, lying down to read many teenagers like to lie in bed to read books, which is a bad habit. Because the human eye should be kept horizontal state reading books, so that the regulation and collection (convergence) to achieve consistent, reduce eye fatigue. If lying down to read, both eyes are not in the horizontal state, eye and book distance is not consistent, both eyes are not consistent with the line of sight up and down, uneven illumination on the book, will make the eye regulation tension and easy to move the book close to the eye, which can increase the eye burden 2-3 times, the formation of myopia over time. 6, sleep deprivation, the next day’s spirit, dizziness, the brain is not fully rested.