What is myopia

Abstract: the epidemiological study of close work shows that visual proximity load is the most important cause of simple myopia in children. Visual proximity load includes too close eye use and too long visual proximity time. There is dose gradient effect in the occurrence and development of close work and myopia.

myopia is a symptom that the eyes can’t see far objects but see near objects clearly. On the premise of static refraction, distant objects can’t converge in the retina, but form a focus in front of the retina, resulting in visual deformation and blurring of distant objects. Myopia can be divided into refractive and axial myopia, among which refractive myopia is the most serious. High myopia is when refractive myopia reaches more than 600 degrees.

clinical manifestations of myopia

1 The far vision decreased and the near vision was normal;

  2. Visual fatigue;

  3. Exophoric exotropia or co rotational exotropia can occur. Most strabismus eyes are one with high myopia;

  4. People with high myopia often have vitreous liquefaction and turbidity, complicated with cataract, and consciously feel the dark shadow fluttering in front of their eyes or vision loss;

  5. The fundus of low and moderate myopia is generally unchanged or leopard shaped fundus, myopic solitary spot, atrophy of temporal or peripheral annular choroid of optic nerve papilla, macular degeneration, bleeding Fuchs’ macula, posterior scleral staphyloma, and prone to retinal tears and retinal detachment;

6. High myopia slightly protrudes due to the long axis of the eye, with deep anterior chamber and large pupil, and slightly dull light reversal;

7. Concave spherical lens can improve vision.

causes of myopia

I. environmental factors

1 Epidemiological studies on close work show that visual proximity load is the most important cause of simple myopia in children. Visual proximity load includes too close eye use and too long visual proximity time. There is dose gradient effect in the occurrence and development of close work and myopia. The prevalence of myopia in students with long reading time is higher than that in students with short reading time. The more reading and close working hours, the faster the progress of myopia (P < 0.001); The nearer the reading distance, the faster the progress of myopia (P = 0.002). The consistency of diopter among siblings decreased with the increase of age difference. The odds ratio (or) was 5 for those with a difference of 2 years and only 2.5 for those with a difference of 10 years. Because the genetic background of siblings is similar regardless of the age difference, and the contrast ratio decreases with the increase of age difference, the most reasonable explanation is that the siblings with small age difference are more similar to the environment exposed than those with large age difference.

  2. Nutrition and diet

diet plays an important role in body development. Many people believe that malnutrition is one of the causes of myopia. Malnourished infants can have emmetropia earlier, which is very easy to develop into myopia. Studies have shown that vegetarians have a high prevalence of myopia. The lack of high sugar, high protein and some trace factors may be related to the formation of myopia. The contents of copper and zinc in hair were measured by atomic absorption spectrophotometer. It was found that the zinc / copper ratio of amblyopia patients, abnormal ocular axis and poor far vision was significantly lower than that of normal vision (P < 0.05). In addition, the study also found that the energy intake, protein, fat, vitamin B1, B2 and C, phosphorus, iron and cholesterol of children who developed myopia were significantly lower than those who did not develop myopia.

  3. Regional differences and socio-economic factors

and

the prevalence of myopia in urban areas is significantly higher than that in rural areas, which becomes more obvious with the increase of age. Rural life is closer to nature and the air is fresh. This is related to their living standards, living environment and diet and nutrition. And rural students have less opportunities to watch TV and use computers.

  4. Illumination and reading posture

have different opinions on the effect of light on human eye. The visual changes of students in 10 key middle schools after using desk lamps have been observed, which shows that poor local lighting will affect their visual acuity. Moreover, the greater the brightness contrast between the environment and the working surface, the easier it is to cause visual fatigue. Incandescent lamps have a greater impact on vision than fluorescent lamps. There are also studies that lighting has nothing to do with myopia. Poor reading posture of

and

can also cause vision loss. The closer the reading distance, the greater the inclination of the neck. This posture darkens the visual surface close to the reader by the occlusion of the head, causing ipsilateral pupil expansion and affecting vision. At present, there are few studies on this aspect, and it is not sure whether poor reading posture is the cause or result of myopia.

2. Genetic factors

myopia is a kind of eye disease related to heredity. The research on the genetic problem of myopia began very early, and there are many opinions. Such as recessive inheritance, multifactorial inheritance, etc. Low myopia is multifactorial inheritance, while high myopia is single factor inheritance; Simple myopia and a few pathological myopia are autosomal dominant inheritance, and most pathological myopia are recessive inheritance.

Duke elder proposed the role of heredity very early. (1) Ametropia can be inherited; (2) The transmission of genetic characteristics is determined by multiple factors; (3) The heritability of low and high refractive errors is different; (4) The refractive properties of eyes are mainly determined by heredity rather than environmental factors; (5) Twins as the research object is of great significance; (6) Different types of refraction have different genetic types; (7) The genetic facts of < 4D myopia are highly consistent in monozygotic twins, mainly autosomal dominant inheritance, and others believe that recessive inheritance. The twin study found that the heritability of myopia was 0.58-0.91. Zadnik et al. Showed that the correlation between parents' myopia history and children's ametropia was closer than that between children's close work and their ametropia. The problem is that while children inherit genetic factors such as eye size and shape, they may also follow their parents' eye habits or postures.

III. eye factors

1 Visual deprivation

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can induce myopia, such as congenital cataract, blepharoptosis, corneal lesions, posterior lens fiber hyperplasia and optic neuropathy. However, axial myopia caused by eyelid covering in infants is the result of mechanical effect or thermal effect, not the result of abnormal visual input.

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