What Are the Different Myopia Causes?

In the relaxed state of adjustment, the parallel light is focused by the eye refractive system before the retina, called myopia. Myopia is also called shortsightedness, because this kind of eyes can only look near and not far. When this eye is at rest, the parallel light from infinity passes through the refractive system of the eye, and then it gathers into focus in front of the retina. On the retina, an unclear image is formed. Far vision is significantly reduced, but near vision Still normal.

Basic Information

nickname: myopia
English name: nearsightedness
English alias: myopia

Visiting department: Ophthalmology
Multiple groups: Copy workers or other close-up workers
Common causes: Genetics, development, close work, etc.
Common symptoms: Reduced distance vision, visual fatigue, etc.

Causes of myopia

Internal cause

(1) Genetic factors Myopia has been recognized to have a certain genetic predisposition, especially for high myopia. But for general myopia, this tendency is not very obvious. Those with genetic factors have an earlier age of illness, and their degrees are above 600 degrees. But there are also people with high myopia and no family history. High myopia is an autosomal recessive inheritance, and general myopia is a multifactorial genetic disease.

(2) Developmental factors Babies are hyperopia due to their smaller eyeballs, but with the increase of age, the axis of the eye gradually grows, and they develop normally after the age of 6 years. If over-development occurs, myopia is formed. This type of myopia is called simple myopia, which usually starts at school age, and is generally lower than 600 degrees. Development stopped around the age of 20. Such as the rapid progress in childhood, 15 to 20 years of age progress more quickly, and then slow down, this type of myopia is often higher than 600 degrees, can reach 2000 to 2500 or 3000 degrees. This myopia is called high myopia or progressive myopia or pathological myopia. This type of myopia can cause degenerative changes in old age, so vision can gradually decrease, and optician cannot correct vision. But very few are congenital and have myopia at birth.

External cause

That is to say, environmental factors, people who are engaged in text work or other short-distance work have more nearsightedness, and more young people have nearsightedness. From the fifth and sixth grades of elementary school, the prevalence has increased significantly. This phenomenon shows that the occurrence and development of myopia are closely related to close work. Especially the eyeballs of adolescents are in the stage of growth and development, with strong adjustment ability, and the extensibility of the ball wall is relatively large. The adjustment and collective action during close work such as reading makes the medial rectus muscle exert a certain pressure on the eyeballs. The internal pressure also rises accordingly. As the work continues to increase, the frequency and time of adjustment and assembly gradually increase. The ciliary muscle and extraocular muscles are often in a high tension state. Excessive regulation can cause ciliary muscle spasm. , Causing temporary vision loss. However, after rest or the use of ciliary muscle erosion agents, vision may improve or fully recover. Therefore, some people call this myopia as functional myopia or pseudomyopia.

Clinical manifestations of myopia

Vision

The most prominent symptom of myopia is distant vision, but myopia is normal. Although the higher the degree of myopia, the worse the distance vision, but there is no strict ratio. Generally speaking, nearsightedness above 300 degrees, far vision will not exceed 0.1; 200 degrees is between 0.2 and 0.3; 1.00D can reach 0.5, which may be better sometimes.

Visual fatigue

It is common in low-level patients, but not as obvious as in hyperopia. It is due to the inconsistency between regulation and collection. In high myopia, because the fixation target is too close to the eye, the collective effect cannot be matched with it, so monocular fixation is used instead, which will not cause visual fatigue.

3. Eye position

Because myopia does not require adjustment when nearsighted, the collective function is relatively weakened. When the muscular balance cannot be maintained, the visual function of both eyes is destroyed. Only one eye sees the other and the other eye is biased to the outside. Squint. If the visual function of the deviated eye is extremely poor, and the deflection occurs earlier, the deviated eye can lose its fixation ability and become monocular exotropia.

4. Eyeball

High myopia, mostly belongs to axial myopia, the anterior and posterior axis of the eyeball is elongated, and its extension is almost limited to the posterior pole. Therefore, it often shows that the eyeballs are more prominent, the anterior chamber is deeper, the pupils are large, and the reflection is slower. Because there is no regulated stimulus, the ciliary muscles, especially the annular part, become atrophic. In extremely high myopia eyes, the lens can not support the iris at all, so mild iris tremor occurs.

5. Fundus

The fundus changes of low myopia are not obvious, and high myopia can cause degeneration of the fundus due to excessive extension of the eye axis.

(1) The blood vessels in the retina of the leopard-like fundus become thinner and straighter after leaving the optic disc. At the same time, due to the elongation of the choroidal capillaries, the nutrition of the retinal pigment epithelium can be affected, so that the superficial pigments disappear and the choroidal vessels are exposed, forming Leopard-shaped fundus.

(2) The choroid around the optic disc of myopia is pulled away from the temporal side of the nipple under the traction of the scleral extension, and the sclera behind it is exposed, forming a white curved spot. If the posterior pole of the eyeball continues to extend, the disengagement of the choroid gradually extends from the temporal side of the nipple to the periphery of the optic disc, and finally a ring-shaped spot is formed. In this spot, irregular pigments and hardened choroidal blood vessels can be seen.

(3) Irregular, isolated or fused white atrophy spots can occur in the macula, and bleeding can sometimes be seen. In addition, there are occasional degeneration lesions near the macula, which appear as a black ring-shaped area, slightly smaller than the optic disc, with clear boundaries, and small circular bleeding can be seen at the edges, called Foster-Fuchs spots.

(4) The extension of the posterior scleral uvular eyeball is limited to a small part, and a sharp protrusion can be seen from the slice, which is called the scleral uvular tumor. This atrophic lesion, if it occurs in the macula, can be combined with central vision impairment.

(5) The edge of the cystic degeneration retina of the serrated margin is the serrated margin. It is formed by the intersection of multiple layers of retina and single layer of ciliary body non-pigmented epithelium. It shows that there is omental defect and cystic change at the junction between the flat part and the retina.

Myopia

Eye examination includes naked eye vision, corrected vision, intraocular pressure measurement, etc., and computer optometry and dilated pupil examination. Corneal mappers, corneal thickness gauges, slit lamps, etc. are also used to check the cornea, refractive interstitial, fundus, corneal thickness, and radius of curvature.

Myopia diagnosis

Myopia can be clearly diagnosed through mydriasis and optometry.

Myopia treatment

Wear glasses

An appropriate concave lens is placed in front of the near-sighted eye, and the parallel light beam is dispersed into the eye after passing through. The focus therefore moves backward and falls directly on the retina to obtain clear far vision. The principle of selecting the power of the concave lens for correcting myopia is to select the lens with the smallest power as the eye lens from several concave lens lenses that obtain normal vision (1.0 to 1.2) or the most satisfactory vision (that is, the best vision when the correction is less than 1.0). Correction degree.

In addition to correct vision, concave lenses can restore the balance of adjustment and collection, relieve visual fatigue, prevent or correct strabismus or amblyopia, reduce refractive errors, and help establish and develop the function of binocular co-vision. May prevent deepening of diopters.

2. Surgical treatment

The surgical treatment of myopia has been widely used in recent years at home and abroad. There are many types of surgery, which can be divided into:

(1) Corneal surgery includes excimer laser in situ keratomileusis (LASIK), excimer laser keratotomy (PRK), radiation keratotomy, and less commonly used automatic laminoplasty, corneal ring placement, Surface corneal transplantation, corneal lens surgery, etc. This type of surgery is generally used for those who have stopped developing myopia. Surgery can correct myopic refractive error by changing the curvature of the cornea, but it has no effect on the fundus changes and various complications of pathological myopia.

(2) Lens and intraocular lens surgery Clear lens removal for highly myopic eyes has a long history of correcting refractive errors, but attention should be paid to complications such as retinal detachment and macular edema after surgery. In recent years, phacoemulsification combined with intraocular lens implantation has been effective. Some people with high myopia who have a transparent lens put an anterior chamber or posterior chamber intraocular lens in front of the lens to correct the refractive error and have achieved a certain correction effect. This method has a strong ability to correct refractive errors. For high myopia above 1200 degrees, the cornea is thinner. It is estimated that it may be more suitable for those who have difficulty in correcting corneal refractive surgery.

(3) Posterior scleral reinforcement for progressive pathological myopia uses wide fascia, allogeneic scleral bands, dura mater or silicone sponge to bypass the posterior pole to strengthen the posterior sclera, hoping to prevent myopia from progressing and Reduce the occurrence of fundus complications.

3. Drug treatment

There are a variety of drugs used to treat myopia, including atropine, neostigmine, and tropinamide.

4. Other treatments

Other treatments that are harmless to the eye and have a certain theoretical basis, such as haze, binocular and combination imaging, telescope, and ciliary muscle exercises can be tried.