Abstract: “true myopia” is caused by abnormal ocular structure. When the eyes are in close working state, the eyeballs will converge inward under the action of extraocular muscles and become mild “eye to eye”, otherwise there will be ghosting when looking at near objects.
rumor: myopia and aging can offset each other. If you have a little myopia when you are young, you won’t get presbyopia when you are old.
truth: the pathogenesis of myopia and presbyopia cannot offset each other. Especially for the young people with high myopia, at the age of presbyopia symptoms and the need to wear presbyopic glasses, they still need to wear myopia glasses when looking at a distance, but the degree of myopia may be reduced.
if you read books and computers for a long time, your ciliary muscles will often be in a state of tension and gradually adapt to this state. If you look at the distance at this time, the ciliary muscles will not relax when they are used to tension, and the lens can’t become flat and tense. The excess positive degree of this part will make normal people feel like wearing a pair of reading glasses and can’t see things far away. You need to look closer. It is equivalent to that the camera is temporarily locked in “close range mode”, and the distant things are blurred. We call it “myopia”.
in this case, the eyedrops of atropine can paralyze the ciliary muscle, force it to relax, make the lens tense and thin, which is equivalent to removing this part of the excess positive degree, and you can see things in the distance. This kind of myopia that can return to normal is called “pseudomyopia”. When you go to the hospital with glasses, the doctor will first give you “mydriatic optometry” in order to eliminate the reversible degree of pseudomyopia. “Mydriasis” is a drug that paralyzes the ciliary muscle. At the same time, it can also paralyze the pupil muscle and dilate the pupil.
and “pseudomyopia” are reversible and can be eliminated. What about “true myopia”? “True myopia” is caused by abnormal eye structure. When the eyes are in close working state, the eyeballs will converge inward under the action of extraocular muscles and become mild “eye to eye”, otherwise there will be ghosting when looking at near objects. In this state for a long time, the extraocular muscles will compress around the eyeball, lengthen the anterior and posterior diameter of the eyeball, and the ball becomes an ellipsoid. This change cannot be reversed. When the anterior posterior diameter of the eyeball becomes longer, less refractive power is required for imaging. When looking at the distance, no matter how relaxed the ciliary muscle is, it can not thin the lens and remove the excess reading glasses. Therefore, the image that should have been projected to the retina is projected to the front of the retina and cannot be focused on the retina. This kind of myopia that can no longer be reversed through self-regulation is called “true myopia”. If the degree of myopia is too high, the eyeball is too “elliptical”, the front and rear are sharp, and the retina is not firmly attached to it. If it is forced too hard or hit, it is easy to have retinal detachment, resulting in blindness. What about
hyperopia is usually caused by abnormal eye structure. Because the eyeball of young children is not fully developed, the anterior and posterior diameter of the eyeball is short, and the object reaches the retina before imaging, it can not become a clear image. Therefore, under 7 years old is the high incidence age of hyperopia. In order to see close objects, the ciliary muscle needs to be in a state of tension frequently to make the lens relax and achieve sufficient refractive power. Therefore, hyperopia eyes are prone to eye fatigue. When the degree of hyperopia is large, due to the excessive tension of ciliary muscle and the convergence of binocular reflex, it is easy to develop into esotropia for a long time, that is, “cockfighting eye”. Mild hyperopia below
300 degrees generally does not need correction, but those with visual fatigue or esotropia should be corrected with convex lens as soon as possible. Convex lens has the function of converging light, so the degree is positive, which can make up for the diopter lacking in hyperopia. Preschoolers with high degree of hyperopia should also have optometry and glasses as soon as possible. However, with the growth of age and the development of eyeballs, the light should be re examined once a year to reduce the power of lenses in time to meet the needs.
presbyopia looks like hyperopia, but it’s far from the same thing.
myopia and hyperopia are mostly caused by abnormal anterior and posterior diameter of the eyeball, while presbyopia is completely caused by decreased refractive ability of the lens. Presbyopia, the scientific name of presbyopia, means that the elasticity of the lens becomes worse with age, and no matter how tense the ciliary muscle is, it can’t relax; Or the ciliary muscle itself is aging, and it’s not very nervous. Therefore, the adjustment ability of the lens with more than 1000 degrees will lose 50 ~ 100 degrees every five years, resulting in insufficient adjustment ability when looking close, and insufficient refractive power. The object reaches the retina before imaging. It also needs to wear convex lens to supplement refractive power for correction.
hyperopia and presbyopia seem to have the same correction methods, but they are not the same thing. Hyperopia is mostly due to the short anterior posterior diameter of the eyeball, while presbyopia is caused by the aging of the lens and ciliary muscle and the decrease of refractive power. Hyperopia often occurs in children. Usually, the correction degree decreases year by year. When the degree is not high, you can get a clear image through self-regulation regardless of looking close and far; Presbyopia generally occurs in the middle-aged and elderly. The correction degree increases year by year with age, and due to the decline of adjustment ability, even if the degree is not high, objects close to a certain distance cannot be seen through their own adjustment, and must be moved away.
have myopia. Won’t they be old when they are old?
from the above words, you must understand that people can not be short-sighted or farsighted, but they can’t escape presbyopia. That got myopia, old don’t need to wear presbyopic glasses? It depends. If the degree of myopia is low when you are young, for example, you have a myopia of 50 ~ 100 degrees, and you are used to not wearing glasses at ordinary times, congratulations. When peers start wearing reading glasses, you need to wear reading glasses 5-10 years later than them. Because your “reserve” myopia refractive power can offset some of the refractive power lost by presbyopia, but you may still need to wear reading glasses with age.
are miserable for people with high myopia. Because the pathogenesis of myopia and presbyopia cannot offset each other, at the age when presbyopia symptoms occur and presbyopia glasses are needed, you still need to wear myopia glasses when looking at a distance, but the degree of myopia may be reduced. When looking close, due to the of the lens