I. What is myopia? What is myopia: When parallel light rays are focused in front of the retina by the refractive system of the eye in a relaxed state of adjustment, it is called myopia. This is because the eye can only see near and not far. When the eye is at rest, parallel light from an infinite distance is refracted by the refractive system of the eye and assembled into a focal point before the retina, while on the retina it is knotted into an unclear image. II. (1) Genetic factors Myopia has been recognized to have a certain genetic predisposition, especially for high myopia. However, for general myopia, this tendency is not so obvious. High myopia is an autosomal recessive inheritance, while general myopia is a multifactorial inheritance disease. (2) Developmental factors Infants are farsighted because their eyes are small, but as they grow older, the eye axis gradually lengthens and develops normally after age 6. If the development is excessive, myopia will be formed, and this kind of myopia is called simple myopia, which mostly starts in school age and is usually less than 600 degrees. The development stops at the age of about 20. If myopia progresses rapidly in early childhood, it progresses more rapidly at the age of 15 to 20, and then slows down. This kind of myopia is called high myopia or progressive myopia or pathological myopia. This kind of myopia can degenerate in later years, so the vision can be gradually reduced, and the glasses can not correct the vision. However, there are very few congenital cases, where myopia is present at birth. 2. External factors, i.e. environmental factors, are more frequent among people who work in writing or other close work, and among teenage students, whose prevalence increases significantly from the fifth or sixth grade. This phenomenon shows that the occurrence and development of myopia is very closely related to close work. In particular, the eye of adolescents is in the growth and development stage, with strong adjustment ability and large extension of the spherical wall. The adjustment and collection of reading and other close work make the internal rectus muscle exert a certain pressure on the eye, and the intraocular pressure rises accordingly. Over-exertion can cause spasm of the ciliary muscle, resulting in a temporary loss of visual acuity. However, after rest or the use of ciliary muscle erosion agents, vision may improve or recover completely. Therefore, some people call this myopia functional myopia or pseudomyopia. III. Clinical manifestations of myopia: 1. Visual acuity The most prominent symptom of myopia is a decrease in distance vision, but near vision can be normal. Although, the higher the degree of myopia, the worse the distance vision, there is no strict ratio. Generally speaking, for myopes with more than 300 degrees, the distance vision will not exceed 0.1; for those with 200 degrees, it is between 0.2 and 0.3; for those with 1.00D, it can be 0.5, and sometimes it may be better. 2. Visual fatigue is especially common in low vision, but not as pronounced as in hyperopia. It is due to the incoordination of adjustment and assembly. High myopia because the target is too close to the eye, the role of the collection can not cooperate with it, so more monocular gaze, but will not cause visual fatigue. 3. Eye position Because myopic eyes do not need to adjust when they look close, the collection function is relatively weakened, and when the muscle balance cannot be maintained, the visual function of both eyes is destroyed, and only one eye sees things, and the other eye is deviated to the outside, becoming a temporary alternating strabismus. If the visual function of the deviated eye is extremely poor and the deviation occurs early, the deviated eye may lose the ability to fix the vision and become monocular exotropia. Highly myopic eyes are mostly axially myopic, with the anterior and posterior axes of the eye elongated, and their elongation is almost limited to the posterior pole. Therefore, the eye is often more prominent, the anterior chamber is deeper, and the pupil is large and the reflexes are dull. The ciliary muscle, especially the annular portion, becomes atrophied due to the absence of regulatory stimulation, and in very high myopia, the lens may not support the iris at all, resulting in mild iris tremor. 5. Fundus The fundus changes are not obvious in low myopic eyes, but in high myopic eyes, the excessive elongation of the eye axis can cause degenerative changes in the fundus. IV. Examination and diagnosis of myopia Ocular examination includes naked eye visual acuity, corrected visual acuity, intraocular pressure measurement, fundus examination, etc. Computerized optometry and dilated pupil examination are used. The cornea, refractive interstitium, fundus, corneal thickness and radius of curvature are also examined by corneal map, corneal thickness meter and slit lamp. Myopia can be clearly diagnosed through dilated pupils and optometry. The treatment of myopia 1. Wearing glasses A proper concave lens is placed in front of the myopic eye, the parallel light beam is dispersed into the eye after passing through, so the focal point is shifted back and falls on the retina, and clear distance vision can be obtained. The principle of selecting the corrective concave lens for myopia is to select the smallest of several concave lenses that will give normal vision (1.0-1.2) or the most satisfactory vision (i.e., the best vision when corrected to less than 1.0) as the corrective lens for the eye. In addition to improving visual acuity, concave lenses with the correct prescription can restore the balance between accommodation and assembly, relieve visual fatigue, prevent or correct strabismus or amblyopia, reduce refractive error, and help establish and develop binocular synoptic function, and prevent refractive deepening in myopic astigmatism. 2. Surgery The surgical treatment of myopia has been commonly used in recent years at home and abroad. (1) Corneal surgery includes excimer laser in situ keratomileusis (LASIK), excimer laser keratomileusis (PRK), radioactive keratotomy, and the less commonly used automated lamelloplasty, corneal ring placement, surface keratoplasty, and corneal lens surgery. These procedures are generally used for people whose myopia has stopped progressing. Surgery can correct myopic refractive errors by changing the curvature of the cornea, but it does not work on the fundus changes and various complications of pathological myopia. (2) Lens and IOL surgery has a long history of clear lens extraction for high myopia to correct refractive error, but attention should be paid to the possibility of postoperative complications such as retinal detachment and macular cystoid edema. In recent years, ultrasound emulsification combined with IOL implantation has been used with good results. Some people have also placed an anterior or posterior chamber IOL in front of the lens to correct refractive error in high myopia with a clear lens, which has also achieved some corrective effect. This method is more capable of correcting refractive error and may be more suitable for those with high myopia of 1200 degrees or more and thin corneas, which are not easily corrected with keratoconus surgery. (3) Posterior scleral reinforcement for progressive pathological myopia with broad fascia, allograft scleral strips, dura mater or silicone sponge around the posterior pole of the eye for posterior scleral reinforcement, hoping to prevent myopia from progressing and reduce the occurrence of fundus complications. Medications There are a wide variety of medications that have been used to treat myopia, including atropine, neostigmine, tropicamide, etc. Other treatments that are not harmful to the eye and have some theoretical basis, such as fog vision method, binocular synoptic method and synoptic image intensifier, far-seeing method, ciliary muscle exercise method, etc. can be tried.