Internal factors
Genetic factors: Myopia has a certain genetic tendency, especially in people with both parents being highly myopic (6.00D or more), which is a multi-factorial genetic disease with autosomal invisible inheritance. This part of the population is affected at an early age, with some developing 3 or 4.00D myopia at the age of 4-5. However, there are also people with high myopia with no family history.
Developmental factors: Infant eyes are mostly farsighted, and as they grow older, the eye axis gradually lengthens until it is roughly equal to that of an adult at about 7 years of age, and myopia can develop if overdeveloped at an early age. Very few people are born with myopia, but very few are congenital.
External factors
The eye of adolescents is in the stage of growth and development, with strong adjustment ability and large stretching of the spherical wall. The adjustment and collection during close work such as reading, writing, watching TV, e-books, computers, etc. often put the ciliary muscle and extraocular muscles under high tension, and the overplay of the adjustment can cause spasm of the ciliary muscle, thus causing a temporary loss of vision.
However, after rest or the use of ciliary muscle paralyzing agents, vision may improve or even recover completely. This type of myopia is functional myopia or pseudomyopia. This state of the eye can be treated by controlling eye use, medication to relax the ciliary muscle, and improving the visual environment to relieve myopia.
However, the scleral tissue, under the long-term mechanical pressure of the extraocular muscles, exerts a certain pressure on the eye so that the intraocular pressure also rises accordingly, the spherical wall gradually extends, the eye axis elongates, and the myopia becomes deeper and deeper, and it can no longer be relieved by atropine, etc. True myopia is formed.
Another important cause of myopia in children is sleeping with the lights on at night, which prevents the eyes from truly relaxing because there is still a certain amount of light shining into the eyes through the eyelids, making the eyes still in working condition. Myopia is formed over time.
A prospective study was conducted to examine the role of environmental and genetic factors in the development of myopia, and students who had normal vision were analyzed at a follow-up visit two years later to determine the factors affecting myopia. The results showed that the ratio of new myopia prevalence was 1:2.6:3.8 among children with both parents without myopia, one parent with myopia, and both parents with myopia, and the ratio of new myopia prevalence was 1:2.1:3.2 among children with environmental factors: 1 to 2 h:3 h:4 to 5 h of reading time after school. Therefore, genetics and environment are two important factors that influence the occurrence of myopia in students.
Prevention of myopia
1. Avoid using the eyes too close to each other and for too long.
To prevent excessive eye use, it is appropriate not to work at close range for more than 50 minutes at a time, and to take a 10-minute break every hour to relax the adjustment of the extreme eyes, which can prevent myopia. Often do eye exercises, to prevent myopia also has a certain role.
2, lighting light can not be too strong or too weak.
The classroom should have good lighting conditions, tables and chairs should be appropriate height, the classroom size is appropriate, the distance of the blackboard should be moderate, not near 2 meters, far not more than 6 meters, the distance between the eyes and books when studying to maintain at 30-35 cm, the blackboard should not be reflective, the print used should be clear, the contrast should be sharp, students seated in front, behind, left and right to be regularly switched.
3, do not read books on the line or while walking.
Walking side reading or reading in the walking carriage, 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.
4, do not be picky eaters, do not eat too much sugar.
5, do not lie down to read books.
Many adolescents like to lie in bed to read, the eyes are not in the horizontal state, eye and book distance is not consistent, will make the eye regulation tension, and easy to move the book closer to the eyes, which can increase the burden on the eyes 2-3 times, the formation of myopia over time.
6, sleep enough.
When sleep deprivation, mental discomfort, dizziness, the brain does not have sufficient rest, fatigue is not eliminated, increasing the burden on the eyes, prompting the occurrence of myopia.
7, desk and chair height ratio is appropriate, writing posture.
If the desk and chair is too low, so that the head tilted forward, the spine bent, the chest is pressed, the eyes adjust relatively tense. Or desks and chairs too high, feet hanging, the lower limbs are easy to swing, can not maintain the correct posture, can make eye fatigue, over time, it is easy to occur myopia.
8, avoid video terminal syndrome.
Watching television, often play video games, playing computer is easy to make eye muscle fatigue, too long operation caused by eye dryness and fatigue, can directly cause eye myopia, need to properly control the use of time.
9, pay attention to diet and nutrition, eat more food containing vitamin A, such as goat liver, pig liver, eggs, milk, carrots, vegetables, etc.. Promote outdoor activity rest and frequent far-seeing, 3-4 times a day, at least five to ten minutes each time.
10, eye exercises function is through self-massage acupuncture points around the eye, so that the eye blood circulation smoothly, to activate blood, antispasmodic, to avoid ciliary muscle tension spasm purpose. Every day before the third class in the morning, before the second class in the afternoon adhere to the two exercises to relax the eye muscle, to protect the role of vision.