Every year, during the summer and winter, a large number of parents bring their children to the Optometry and Refractive Center of Beijing Tongren Hospital for optometry and laser refractive surgery for myopia. As an ophthalmologist specializing in refraction, seeing the anxious parents and the large number of patients who need glasses and laser myopia surgery, I feel deeply responsible for the high incidence and seriousness of myopia in China. This article briefly introduces the basics of myopia, including the factors of myopia, prevention and correction.
1. The incidence of myopia
The incidence of myopia in China is high.
The domestic and foreign literature is that China and Japan are countries with a high incidence of myopia; ethnic groups with late cultural development, such as Libyans and Eskimos, have a high incidence of hyperopia; ethnic minorities such as the Uyghurs in China used to have almost no myopia, but in recent years, with the increase in school-age children, myopia has also occurred. The incidence of myopia in primary and secondary schools increases gradually with school age. According to a national survey in 1985, the prevalence of myopia was higher in universities (66.6%) > high schools (61.19%) > junior high schools (34.85%) > elementary schools (12.27%), and it was found that the prevalence of myopia was higher in urban schools, key schools, students with better academic performance and more visual acuity than in rural areas, non-key schools, students with poorer academic performance and less visual acuity. The prevalence of pathological myopia is 1.0%. Recently, the Beijing Municipal Health Bureau reported that in recent years, the number of students with poor eyesight in high school and high school examinations has remained high, and the visual acuity of young people in urban areas is worse than that in distant suburban areas and counties, and the incidence of myopia among junior high school students is 46%, which is a further increase than in 1985.
2. Causes of myopia
There are many factors affecting the development of myopia, and the main factors are broadly classified as genetic factors, environmental factors and nutritional and physical factors.
(1) Genetic factors.
Myopia has a certain genetic predisposition. High myopia has a more pronounced hereditary tendency than general myopia. Those with genetic factors have an early onset of myopia, often starting before puberty, and are more than 6 diopters (-600 degrees). This high degree of myopia is medically called pathological myopia. The occurrence of high myopia in China is an autosomal recessive inheritance, which means that if both parents are highly myopic, 100% of the offspring will be highly myopic. If one parent is highly myopic, 50% of the children are highly myopic, but there are also manifestations of incomplete vision. Environmental factors play a role. In general, myopia is a multi-factorial inheritance, which obeys the law of heredity and has the participation of environmental factors.
(2) Environmental factors.
Environmental factors are mainly close work and poor working environment, from a large number of domestic and foreign related research reports point out that environmental conditions are objective factors that determine the formation of myopia. However, under the influence of close reading or close work, why can myopia be produced? There is no unanimous understanding of this, and there are several theories.
A. Regulation theory: The majority of myopia occurs in adolescence, because the regulation of adolescent eyes is particularly strong and highly adaptive to close work and learning, so it is not easy to look close and fatigue. However, if the ciliary muscle is overstressed for a long time, the ciliary muscle will become fatigued or even spasm and regulating myopia will occur. This may affect the lengthening of the eye axis through other means.
B. Environmental adaptation theory: In early childhood, the eye is small and most of the eyes are farsighted, and as the eye grows older, it becomes orthophoric. During this developmental process, the eye becomes myopic due to excessive close reading and the need to adapt to this adjustment. During development, external factors such as lighting, reading posture, contrast, small blurred words, too close and long reading time can affect the incidence of myopia.
(3) Nutritional constitution theory: From some data analysis, the lack of trace elements such as cadmium, strontium and zinc and the weak constitution can also affect the occurrence of myopia, but there are different opinions on how these factors affect myopia.
In conclusion, it can be seen from the above that myopia can be caused by many factors, both external factors and internal physical factors, rather than a single factor.
3. The process of myopia
The incidence of myopia begins at school age and increases gradually from elementary school, middle school, high school to college. In newborns, the front and back diameter of the eye is only about 2/3 of that of an adult, so they are all farsighted. However, as they grow older, the eye axis gradually becomes longer as their bodies develop. By the age of about 15, the eye is basically the same as an adult, with an anterior and posterior diameter of 24 mm. If the development is excessive and the eye axis is too long, then myopia is formed. Therefore, the occurrence of myopia mostly starts at school age, and the incidence of myopia gradually increases from elementary school, middle school, high school to college, and stops developing by the age of about 18, when the body matures. However, if myopia progresses rapidly at an early age, it progresses even more rapidly by the age of 15 to 20. Such myopia is often higher than 6 diopters, reaching -2000 to -3000 degrees in individual patients. This myopia is called progressive myopia, or pathological myopia.
4.The impact of myopia on working life
Myopia has a great impact on work and life. Many talented students may lose the opportunity to receive education in their preferred profession and future job opportunities. Nearsightedness can be a stumbling block to life’s development.
In daily life, low and moderate myopia can obtain good corrected vision by wearing frame glasses and contact lenses. The impact on life is not significant. However, patients with high myopia and pathological myopia can have degenerative lesions in their later years, with gradual vision loss, and prescription glasses cannot correct their vision, and individual patients can also develop retinal detachment, macular hemorrhage, macular degeneration, and gradual decline in corrective vision, or even blindness, causing great harm to patients’ vision.
In the workplace, with the development of society, people have higher and higher requirements for visual acuity. Students with a sum of corrected visual acuity below 5.0 in both eyes cannot apply for secondary specialized schools. Students with naked eye vision lower than 5.0 in either eye cannot be admitted to the transportation category of thermal locomotive or the public security category of reconnaissance. Students whose naked eye vision is less than 4.8 in any one eye cannot be admitted to the performance majors of music, dance and drama and acrobatics in the mining class, physical education section.
Seeing, due to the effect of vision, many good students may lose the opportunity to receive education in their favorite majors and future job opportunities. Myopia may become a stumbling block in life development.
5.Prevention of myopia
Developing good eye habits can slow down the occurrence and development of myopia.
Elementary and middle school students should be the important target of myopia prevention. Even if myopia has already occurred, they should follow the fly aspect and cherish their eyes. The first thing to do is to start with the following points.
(1) Make sure that your posture is correct when reading and writing. The distance between books and eyes should be 33cm, do not read while lying in bed or riding in a car, do not read and write in direct sunlight or in places with low light.
(2) Ensure that your eyes have time to rest so that they can grow and develop normally.
(3) Always look into the distance. You can choose distant mountains and trees three to four times a day for about 10 minutes each time.
(4) Do not play video games, watch less TV, and insist on doing eye exercises.
(5) Strengthen physical exercise, pay attention to nutrition, and do not eat partially.
(6) Check your vision regularly, once a semester.
6.Non-surgical correction of myopia
For most people, wearing frame glasses is a good choice. However, be careful to go to a regular hospital or optician when getting glasses. For school-age children and adolescents, they should have an optometry after dilated pupils and then prescription glasses.
(1) Frame glasses, which have been the main method of correcting myopic refractive errors, are now well popularized with resin lenses.
(2) Corneal contact lenses (contactlens, CL) CL is directly attached to the tear layer of the cornea to achieve the purpose of vision correction. Compared with the orbital frame glasses CL has a larger field of view, in all directions of gaze can maintain optical correction performance, eliminate the role of trigeminal glasses, eliminate oblique astigmatism, reduce binocular retinal aberration, maintain better binocular vision, the use of safe, convenient, beautiful, and some special lenses can meet some special requirements.
China’s current correction of myopia to soft contact lens (soft contact lens, SCL) is the main, the main wearing method is the traditional type or frequent replacement type, SCL water content, large diameter, when wearing good adhesion, more comfortable, adaptable, the new progress is to the “daily abandonment type” and The new development is to “daily disposable” and “long wear type” development.
Rigid gas permeable contact lens (RGP) has more superior characteristics, its material oxygen permeability is very high, with good correction of myopia, astigmatism and cone corneal optical properties, safer to use, easier care. More and more myopic patients are beginning to realize the superiority of RGP over SCL.
Orthokeratology lenses (commonly known as OK lenses) are used to reduce the refractive power of the cornea and improve distance vision by mechanically compressing or massaging the cornea to make its central radius of curvature larger. Strictly following medical advice, it can correct patients with non-congenital axial myopia, in addition to meeting the vision requirements of patients with special requirements in some occupations such as athletes, actors, police officers, and patients who are unwilling or unable to use other methods of correction. This method of non-surgical operation does not cause destructive damage to the eye, but the effect is limited and reversible, and cannot fundamentally cure myopia, requiring insistence on long-term wear, but it is a good choice for myopic people with indications, especially for teenagers who may have a role in stopping the progression of myopia.
7.Myopia surgery
Excimer laser surgery is a safe, precise and effective solution for myopia.
The excimer laser is ultraviolet light, which is virtually harmless to surrounding tissues, and is computer-controlled for cutting, whose precision and accuracy is unmatched by any refractive surgery. In particular, new excimer lasers with excellent performance, good spot quality, stable energy output and long operating life have further improved the accuracy and consistency of surgery, and excimer laser surgery has been accepted by the majority of ophthalmologists and myopic patients. Our country has reached the international advanced level in its basic and clinical research, and in some aspects there are our own insights. The introduction of wavefront theory (wavefront) into laser keratomileusis will make it have a more glorious future. The application of the femtosecond laser has placed our country among the world leaders in myopic refractive surgery technological advancement and surgical volume. Myopia laser surgery in China has accumulated a lot of experience and reached the international advanced level. Among them, Beijing Tongren Hospital was the first hospital to introduce excimer laser surgery in China, and it is also the hospital with the most excimer laser surgery in China. (Beijing Tongren Hospital consultation number: 58269073, clinic hours: Monday to Friday morning)
Excimer laser refractive surgery, including excimer laser refractive keratomileusis (PRK), excimer laser subepithelial keratomileusis (LASEK) and excimer laser in situ keratomileusis (LASIK), is the safest and most effective surgical method to correct myopia, and its surgical indications are
(1) Age: generally 18 years of age or older.
(2) Refractive stability: relatively stable refractive error in the past 2 years, the annual increase in refractive error is not greater than 0.50D (50 degrees).
(3) Range of refractive error: myopia preferably not exceeding -15.OOD (1500 degrees) (PRK preferably not exceeding -6.00D); astigmatism preferably not exceeding 6.00D (600 degrees).
(4) Patients with refractive error in both eyes.
(5) Eye examination without active eye disease.
(6) Psychological factors: the patient himself has a healthy psychological state.
(7) Patients who have a requirement for lens removal: do not like to wear frame glasses or corneal contact lenses.
LASIK (excimer laser in situ keratomileusis): the principle is to use a microkeratome to form a corneal flap, and then use the laser to cut the corneal stroma under the flap, after cutting, the cut corneal flap will be restored to its original position. After cutting, the curvature of the cornea is reduced, and the refractive power of the cornea is reduced, thus correcting myopia. However, this surgery is more demanding for the surgeon. To do Lasik surgery, you need to make a corneal flap, which is only about 110 to 130 microns thick, and it is required to be done very well so that the result of the surgery can be very good.
LASlK surgery is currently the safest and most effective surgery to correct myopia, and LASlK surgery has significant advantages over PRK and LASEK.
(1) Scope of application: various degrees of myopia, astigmatism and hyperopia.
(2) The integrity of the corneal epithelium and the anterior elastic layer is preserved, so it is more in line with the anatomical and physiological structure of the cornea.
(3) Postoperative pain is mild, and there is generally no significant ocular pain after PRK.
(4) Fast wound healing, generally good vision can be restored on the first -day after surgery.
(5) Even if the recovery of vision is not satisfactory after surgery, it is easy to adjust.
(6) The duration of postoperative medication is short, only 2 to 4 weeks of hormones are used.
(7) Less refractive regression.
(8) Few postoperative complications.
The most common problem after laser myopia surgery is that patients feel dry eyes during the recovery process after surgery, most of which gradually ease 1 to 3 months after surgery after artificial tear drops are applied. In recent years, as the public becomes more aware of excimer laser surgery, more and more patients are choosing to apply the excimer laser to solve the problem of needing glasses for myopia once and for all.