The cause of myopia is multifaceted. At present, it is generally acknowledged that there are the following reasons.
1.Too close to the eye.
According to relevant data reports, juvenile myopia is mainly caused by long-term eye use distance too close. Teenagers have a strong eye accommodation. When the distance between the book and the eye reaches 7-10 cm, they can still see the object clearly. However, if they often read and write at this distance, the adjustment of the eyes will be extremely tense, thus forming pseudomyopia.
If the long-term over regulation, so that the ciliary muscle can not be flexible expansion and contraction, due to excessive regulation caused by the expansion of the role, so that the extraocular muscle pressure on the eyeball, intraocular pressure increased, intraocular tissue congestion, coupled with youth eyeball tissue delicate, eyeball wall compression gradually extended, eyeball anterior and posterior axis lengthened, exceeding the normal value, the formation of true myopia. The normal reading distance should be 30-35cm.
2.The use of eyes is too long.
Some teenagers read books, write, do homework, watch TV and so on for 3-4 hours without rest. This not only affects the health of the body, but also makes the eyes overburdened. The muscles inside and outside the eyes are in a tense state for a long time and can’t get a rest. After a long time, when looking at a distance, the muscles of the eyes can’t relax and show spasmodic state. Thus, they will feel blurred and form myopia when they look at the distance. This is the reason why some students’ eyesight declines significantly after a holiday.
It is generally recommended to take a rest or look at the distance for 40-50 minutes after reading, writing or watching TV.
3.The lighting is too strong or too weak.
If the light is too strong, such as sunlight on writing, it will cause strong reflection, stimulate the eyes, make the eyes uncomfortable, and it is difficult to see the font. On the contrary, if the light is too weak and the written lighting is insufficient, the eyes can not clearly see the font, the head will move forward, close to the book, and the eye’s pitch is excessive or spasmodic, resulting in myopia.
4.Read while driving or walking.
It’s bad for the eyes. Because the carriage is shaking and the body is shaking, the distance between the eyes and the book cannot be fixed. In addition, the lighting conditions are not good, which aggravates the burden on the eyes. Often this may cause myopia.
Relationship: 40% of myopia is genetic, myopia is mainly inherited from high myopia, high myopia is divided into two types, one is physiological, the other is pathological. Not all myopia is hereditary.