It is estimated that by the end of this century, about 2.5 billion people worldwide will be affected by myopia, which is becoming an epidemic worldwide.
Back then, in high school, Xiao Bian specially counted the myopia rate in the class, each class 50 people, 48 people wore glasses, this terrible myopia rate is heartbreaking.
What is myopia?
In order for our eyes to see, the light is refracted and focused on the retina, and the retina (a layer of light-sensitive cells lining the back of the eye) receives the image formed by these rays and transmits the image to the brain through the optic nerve. When you are nearsighted, the light is focused in front of the retina, not on the retina. You can clearly see nearby objects, but objects in the distance will appear blurred.
Left is normal vision, right is myopia
Eye fatigue, headache, blinking, and difficulty in seeing distant objects are some of the symptoms of myopia. At 8-12 years of age, the symptoms of myopia may be obvious. In adolescence, myopia becomes worse. There is usually no change between the ages of 20 and 40. The deeper the myopia, the higher the risk of various complications, such as: retinal detachment, subretinal neovascularization, cataract, glaucoma and so on.
Why is myopia?
The exact pathogenesis of myopia is still unclear. Most studies suggest that myopia is caused by the interaction of genetic and environmental factors.
For many years, the scientific community has agreed that myopia is mainly attributed to genes. Gene discovery has now linked more than 100 genomic regions to myopia. The myopia of parents has a greater impact on the prevalence of myopia in children, and the probability of myopia in children with myopia is higher. The epidemiological survey in Guangzhou found that parental myopia has an effect on the prevalence of myopia in 15-year-old children. The prevalence of myopia in parents with myopia is twice that of parents without myopia, and both parents have parents who are nearsighted. No three times as many as myopia children.
But it is clear that genes are not the whole cause of myopia. A common perception is that reading and using electronic products is the main culprit in the rise of myopia in recent years. However, in the early 21st century, when researchers began to study specific behaviors, such as the time spent reading books or using computers on a weekly basis, it turned out that these were not the main causes of myopia risk.
In 2007 Donald Muti of Ohio State University School of Optometry in Columbus and his colleagues reported that the only environmental factor closely related to the risk of nearsightedness was the amount of time spent outdoors. Whether they are outdoors, picnics, or just reading on the beach can reduce the likelihood of myopia, the survey found. The researchers even found that children who spent more time outdoors reading books, screens and working close up did not become myopic. Close work may still have some impact, but the most important thing is that exposure to strong light can effectively reduce the likelihood of myopia.
Singapore National Myopia Program / Health Promotion Committee poster encourages children to spend time outside to prevent myopia
How does bright light prevent myopia? The main assumption is that light stimulates the release of dopamine in the retina, which in turn hinders the elongation of the eye during development. The best evidence for the "light-dopamine" hypothesis comes from chicks. In 2010, researchers injected a dopamine inhibitor called spiperone to the eyes of chickens to eliminate the protective effect of glare.
How to treat myopia?
Due to the high prevalence of myopia and its prominence as a public health problem, we urgently need to find ways to effectively treat the speed of myopia development. Through clinical manifestations we know various forms of myopia.
1. Simple myopia: Myopia in normal eyes, less diopter.
2. Degenerative myopia: Also known as malignant or pathological myopia, it is a relatively rare condition that is considered hereditary and is the leading cause of blindness. Photodynamic therapy and laser therapy of combination drugs for the treatment of degenerative myopia, a recent study showed that 7-methylxanthine may eventually cure degenerative myopia.
3. Induced myopia: caused by side effects of various drugs, nuclear hardening, oxygen poisoning or other abnormal conditions.
The most common method of correcting myopia is glasses or contact lenses. They refocus the light on the retina to compensate for the lack of eye. The current use of bifocal or progressive multifocal lenses (PALs) to slow the progression of myopia has produced a therapeutic effect but is relatively weak. Contact lenses have better cosmetic effects and are easy to exercise, but they need to be carefully treated to prevent complications.
In addition to lenses, you can also treat with medication and surgery. Among them, the therapeutic effect of selective M receptor blockers has been confirmed, and applied to clinical drugs mainly include atropine, racemic anisodamine, pirenzepine and tropicamide. However, long-term use of atropine may reduce the effectiveness of the drug, and may also cause a rebound effect when the drug is stopped.
Surgical treatment includes corneal refractive surgery and intraocular lens implantation with a crystal eye. Excimer laser in situ keratomileusis (LASIK) is the most commonly used method for surgical correction of myopia. Intraocular refractive surgery (PIOL) with intraocular lens surgery belongs to intraocular refractive surgery. For patients with ametropia, corneal refractive surgery is not possible, and PIOL surgery is effective.
However, corneal refractive surgery has certain defects: such as the limited range of correction of myopia, corneal bulging may occur after surgery; and intraocular refractive surgery, especially the surgical technique of PIOL, the material of artificial lens, etc. Further research.
Prevention and misunderstanding of myopia
The prevention of myopia is mainly to pay attention to the following points: develop good eye habits, increase the time of outdoor activities, and regularly check eyesight.
Myth 1: Children are too small to wear myopia glasses
Children are in a critical period of visual development. If the myopia is not corrected in time, the long-term retinal blurred image will induce further lengthening of the eye axis, which will increase the myopia and even cause weak and strabismus.
Myth 2: The higher the degree of change in myopia glasses
In addition to genetic factors, environmental factors have also had a major impact on the increase in myopia during adolescence. During the rapid development of the body, the degree of myopia also tends to increase rapidly. Experts recommend that adolescents should have an eye exam every 3 to 6 months and replace the appropriate lenses if necessary.
Myth 3: Myopia can't be matched too clearly
The complete correction of myopia is to correct myopia to face, to restore the normal relationship between regulation and set. Long-term wear of low-correction glasses, on the one hand, easily cause ciliary sputum, that is, artificially increased the degree of myopia, on the other hand, the function of binocular vision is destroyed, only one eye to look at the object, the other eye is biased to the outside, becoming a temporary alternation Strabismus.
There is no scientific evidence that eye exercises, vitamins can prevent or cure myopia. A large number of studies have found that there is a correlation between myopia and intelligence and academic achievement; it is not clear whether there is a causal relationship.
Guidance Professor|Professor of University of Science and Technology of China Doctoral Supervisor Zhang Guoqing
Planning and coordinating|Guo HaoLi Jin Han JuanKnowledge Law Consultant | Chen Huijuan
WeChat account|Netease science person (WYKXR163) / science cat science (kexuemaokepu)
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