Myopia (Myopia) is a condition in which the eye cannot see distant objects, but can see near objects. Under the premise of refractive rest, distant objects do not converge on the retina and form a focal point in front of the retina, resulting in visual distortion and blurring of distant objects. There are two types of myopia, refractive and axial. Refractive myopia is the most severe. Refractive myopia can reach 600 degrees or more, i.e. high myopia.
1.According to the degree of myopia
(1) 3.00D (300 degrees) or less is called mild myopia.
(2) 3.00D ~ 6.00D (300 degrees ~ 600 degrees) is moderate myopia.
(3) 6.00D (600 degrees) or more is high myopia, also known as pathological myopia.
2.According to the refractive component
(1) Axial myopia is caused by excessive development of the anterior and posterior axes of the eye.
(2) Curvature myopia, which is caused by excessive curvature of the cornea or crystal surface.
(3) Refractive index myopia, caused by excessive refractive index of the refractive interstitium.
3. Pseudomyopia
It is also known as regulatory myopia. It is caused by the failure to relax when looking at distance. It is fundamentally different from true myopia, where the refractive component is altered.
4. Mixed myopia
Often a person’s myopia is due to eye fatigue caused by pseudomyopia, resulting in slowly part of the true myopia and pseudomyopia synchronization, so to speak, in the myopia is deepening inside the person, all belong to mixed myopia, the most effective physical means of treating myopia is no more than two, one is surgery, because the current surgical situation is not quite clear sequelae, so the disadvantages have not been able to explain, the advantages are The advantage is that it works quickly.
Etiology of the disease
Myopia is caused by a variety of factors. In recent years, there is much evidence that environmental and genetic factors are involved in the development of myopia: exogenous factors – prolonged close viewing of things causes the ciliary muscle in the eye to lose its elastic lens and cause the lens to fail to recover (thicker than it was born), and myopia occurs.
Genetic factors: Studies have concluded that families with two parents with high myopia have a higher incidence of myopia in the next generation. It is well established that myopia has a certain genetic predisposition, and this is especially true for high myopia. However, the genetic predisposition for general myopia is not so obvious.
Environmental factors: The occurrence and development of myopia is closely related to the use of eyes at close range. The eyeballs of adolescents are in the stage of growth and development, with strong adjustment ability, and the stretching of the eyeball wall is also relatively large. When reading, writing and other close work, not only do the eyes need to play the role of adjustment, but both eyeballs also need to converge, so that the extraocular muscles exert a certain pressure on the eyeballs, and over time, the front and back axes of the eyes may become longer. The majority of this myopia is simple myopia, which is generally lower than 6 diopters, and progresses more slowly around the time of puberty.
Formation
1. Using the eyes too close to each other. According to the data, myopia in adolescents is most often caused by the long-term use of eye distance too close. Adolescents’ eyes have strong regulation, and they can still see clearly when the distance between books and eyes is 7-10 cm, but if they often read and write at this distance, the regulation of their eyes will be abnormally strained, which can lead to refractive (regulatory) myopia, the so-called pseudomyopia. If you over-regulate for a long time, the ciliary muscle cannot stretch flexibly, and the convergence is strengthened due to over-regulation, so that the extraocular muscle exerts pressure on the eye, the intraocular pressure increases, the intraocular tissue is congested, and the youth eye tissue is delicate, the wall of the eye is gradually extended by pressure, the front and back axis of the eye becomes longer than the normal value, and axial myopia is formed, so called true myopia. The normal reading distance should be 30-35 cm.
2, too much time with the eyes. Some teenagers read and write to do homework, watch TV and so on for 3-4 hours without rest, or even to sleep and rest late at night, which not only affects physical health, but also overloads the eyes, the muscles inside and outside the eyes for a long time in a state of tension and do not get rest, over time, when looking at the distance, the eye muscles can not relax and spasm state, so look at the distance to feel blurred and the formation of myopia. Some students’ eyesight declines significantly after a summer vacation for this reason. It is generally advocated that continuous reading and writing or watching TV for 40-50 minutes should be rested for a moment or look into the distance for a while.
3, lighting is too strong or too weak. If the light is too strong, such as sunlight shining written, will cause strong reflection, stimulate the eyes, eye discomfort, it is difficult to see the font, on the contrary, the light is too weak, written lighting is not enough, the eyes can not clearly see the font, the head will be forward, close to the book, the above two cases can be easy eye fatigue, eye regulation is excessive or spasm and the formation of myopia.
4, in the car or walking when reading books. Some adolescents make full use of the time to read books while walking or reading books in the walking carriage, which is very bad for the eyes. Because the carriage is vibrating, the body is shaking, the eyes and the book distance can not be fixed, coupled with poor lighting conditions, increasing the burden on the eyes, often so it may cause myopia.
5, lying down to read a book. Many teenagers like to lie in bed to read, which is a bad habit. Because the human eye should maintain the horizontal state of reading, so that the regulation and collection (convergence) to achieve consistent, reduce eye fatigue. If lying down to read, both eyes are not in the horizontal state, eye and book distance is not consistent, both eyes are not consistent with the line of sight up and down, uneven illumination on the book, will make the eye regulation tension and easy to move the book close to the eye, which can increase the burden on the eye 2-3 times, the formation of myopia over time.
6, sleep deprivation. When sleep deprivation, the next day, the spirit is not invigorated, dizzy, the brain is not fully rested, fatigue is not eliminated, increasing the burden on the eyes, prompting myopia to occur. Sleep deprivation is a very important cause of myopia.
7, desks do not meet the requirements, writing posture is not correct. If the desk and chair is too low, so that the head tilted forward, the spine bent, the chest is pressed, the eyes adjust relatively tense. Or desks and chairs too high, feet hanging, the lower limbs are easy to swing, can not maintain the correct posture, can make eye fatigue, over time, it is easy to myopia.
8, the impact of the current space of the rays. Often watch TV, especially the signal is insufficient, reception rate is not high in rural areas, no shared antenna, the screen is not clear, the snow point is also more, it is easy to make eye muscle fatigue, often play video games students are more likely to damage vision, the mall sold Ze Wang learning machine, can directly cause students myopia, today’s computer computer is an indispensable course, too long operation caused by eye dryness and fatigue prone to myopia. All need to properly control the use of time.
9, the curvature of the cornea or the curvature of the lens behind the front becomes larger, this situation is mostly congenital changes, less common clinically.
What is pseudomyopia?
Pseudomyopia is relative to true myopia. True myopia is a condition in which the refractive system of the orthoptic eye is at rest, i.e., the far point of the eye lies within a finite distance after the effect of accommodation is removed. In other words, myopia is the result of congenital or acquired factors that cause the anterior and posterior diameters of the eye to become longer, and parallel light rays enter the eye and form a focal point in front of the retina, causing blurred vision. Pseudomyopia, on the other hand, is a condition in which there is still partial accommodation when looking at distant objects.
It is common in adolescent students when looking at near objects, because the degree of using regulation is too strong and the duration is too long, resulting in continuous contraction of the ciliary muscle, causing regulation tension or apical spasm, so that after reading and writing for a long time to look at far, can not quickly relax the regulation, and cause dizziness, eye swelling, vision loss and other visual fatigue symptoms. This is called pseudomyopia because the refractive power of the eye is enhanced, leaving the eye in a myopic state. Both pseudomyopia and true myopia are characterized by symptoms of visual fatigue, poor distance vision and good near vision. However, pseudomyopia is a functional change, without the problem of the anterior and posterior diameter of the eye becoming longer, but only the adjustment spasm, after the ciliary muscle paralyzing drug point eye, most can be converted to farsighted or orthoptic eyes. If you wear myopic lenses under true myopia treatment, your eyes will feel very uncomfortable because it does not release the adjustment spasm, and there is even a risk of myopia development.
What is true myopia?
True myopia, also known as axial myopia, is a condition in which the refractive power of the refractive interstitium is normal, the anterior and posterior diameters of the eye axis are extended, and light from a distance is imaged in front of the retina after entering the eye.
The main clinical features of true myopia are.
1. The degree of myopia is mostly moderate or high myopia, which occurs and develops over a long period of time, and the patient has different degrees of emmetropia in the eye appearance.
2. True myopia is difficult to self-adjust and recover.
We believe that the major difference between true myopia and pseudomyopia lies in the normal refraction of the refractive interstitium (cornea, waterproof, lens, vitreous), while the visual axis becomes longer. The main reason for this is long-term near vision.
Symptoms of myopia
1. Vision loss: Myopia is mainly a gradual decrease in distance vision, blurred vision of distant objects and normal near vision, but high myopia is often caused by refractive interstitial clouding and retinal and choroidal degeneration, and its distance and near vision are not good, sometimes accompanied by floating black shadows in front of the eyes.
2. Exotropia: Patients with moderate myopia or above use little or no adjustment when working at close range, which correspondingly weakens the irradiation effect and can induce outward deviation of eye position, forming exotropia.
3. Visual fatigue: Myopic patients have good adjustment power, but need to overuse the convergence power when working at close range, which destroys the balance between adjustment and irradiation, resulting in myopic visual fatigue symptoms. The manifestation of this is eye swelling, eye pain, headache, visual objects have double shadow false edge and other self-conscious symptoms.
4. Eye protrusion: Highly myopic eyes show an outward protrusion of the eyeball due to the growth of the service axis and the enlargement of the eyeball.