Essentials for parents | Basic knowledge on myopia prevention and control for children and adolescents (Part 1)

At present, there are 600 million myopic patients in my country, and the myopia rate among young people ranks first in the world. Due to the increasing burden of primary and secondary school students in and out of class, the popularity of electronic products such as mobile phones and computers, excessive and unhygienic use of eyes, lack of physical exercise and outdoor activities, etc., the myopia rate among children and adolescents in my country remains high and continues to rise. In order to guide local governments in carrying out myopia prevention and control work among children and adolescents, the National Health Commission has issued the "Guidelines for Appropriate Technologies for Myopia Prevention and Control among Children and Adolescents". Let's learn it together.

1. Terminology
1. Visual acuity: also known as visual acuity, refers to the ability of the eyes to recognize objects. It is divided into central vision and peripheral vision (i.e., visual field). The former refers to the visual acuity of the fovea of ​​the macula in the fundus, and the latter refers to the vision outside the macula. Generally speaking, visual acuity refers to central vision. The ability to recognize distant objects is called far vision, and the ability to recognize nearby objects is called near vision.

2. Naked eye vision: also known as uncorrected vision, refers to the vision measured without any optical lens correction, including naked eye far vision and naked eye near vision.
3. Corrected vision: refers to the vision measured after correction with optical lenses, including distance corrected vision and near corrected vision.
4. Poor vision: also known as low vision. Refers to the naked eye vision of children and adolescents over 6 years old less than 5.0 when checking the distance vision according to the Standard Logarithmic Vision Chart (GB11533-2011). Among them, vision of 4.9 is mild poor vision, 4.6≤ vision≤4.8 is moderate poor vision, and vision≤4.5 is severe poor vision. The causes of poor vision in children and adolescents are mostly due to refractive errors such as myopia, hyperopia, astigmatism, and other eye diseases (such as amblyopia, strabismus, etc.).

5. Myopia: refers to the pathological condition in which the parallel light rays from 5 meters away are focused in front of the retina after passing through the eye's refractive system when the human eye is in a relaxed state, which manifests as decreased distance vision.
6. Screening myopia: Use fast and simple methods such as distance vision test, computer optometry under non-ciliary muscle paralysis (commonly known as computer optometry) or string mirror examination to screen out children and adolescents who may suffer from myopia. When children and adolescents over 6 years old have naked distance vision <5.0, they can be judged as screening myopia through computer optometry under non-ciliary muscle paralysis, and the equivalent spherical lens (SE) <-0.50D; in areas where there are no conditions to equip computer optometrists, string mirror examination can be used. When the positive film (convex lens) vision decreases and the negative film (concave lens) vision improves, it is judged as screening myopia.
7. Ciliary muscle paralysis optometry: Ciliary muscle paralysis optometry is commonly known as mydriasis optometry, which is the internationally recognized gold standard for diagnosing myopia. It is recommended that children under 12 years old, especially those who are having their first optometry, or those with hyperopia, strabismus, amblyopia and large astigmatism, must undergo ciliary muscle paralysis optometry. Children who are diagnosed with myopia and need glasses need to have regular re-examinations.

2. Classification of myopia
1. Determine the degree of myopia based on the spherical equivalent (SE) measured by the ophthalmometer after dilation of the pupil. Myopia can be divided into three different levels: low, medium and high according to the SE degree.
(1) Low myopia: -3.00D≤SE＜-0.50D (myopia between 50 and 300 degrees);
(2) Moderate myopia: -6.00D≤SE＜-3.00D (myopia between 300 and 600 degrees);
(3) High myopia: SE < -6.00D (myopia over 600 degrees).
2. According to the progression of myopia and pathological changes, myopia can be divided into simple myopia and pathological myopia.
(1) Simple myopia: mostly refers to myopia that develops during the growth period of the eyeball. When growth stops, the myopia tends to stabilize, and the refractive power is generally within -6.00 D. Most patients have no pathological changes in the fundus, and their vision can be corrected to normal with appropriate optical lenses.
(2) Pathological myopia: It usually refers to the type of myopia that continues to develop after development stops, accompanied by pathological changes in the fundus, also known as progressive myopia. Most patients have a degree of myopia above -6.00 D. Common fundus changes include myopic arcuate spots, lacquer cracks, choroidal neovascularization, macular choroidal atrophy, retinal detachment, posterior scleral staphyloma, etc.

(3) Symptoms and dangers of myopia.
The typical symptom of myopia is decreased distance vision. Its main manifestations include:
(1) Distance vision decreases. Distance vision often fluctuates in the early stages of myopia.
(2) unconsciously squinting or tilting the head when looking at distant objects;
(3) Some people with uncorrected myopia may experience symptoms of visual fatigue;
(4) People with higher myopia, in addition to poor distance vision, often have symptoms such as poor night vision, floaters, floating objects and flashes, and may experience fundus changes of varying degrees. Especially for those with high myopia, the risk of retinal detachment, tear, hole, macular hemorrhage, neovascularization and open-angle glaucoma is increased, and severe cases may lead to blindness.

In addition to these theoretical knowledge, what are the appropriate technologies for myopia prevention and control advocated by the "Guidelines"? We will continue to introduce them in the next article.

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