The pain of myopia, needless to say, is understood.
Five meters away, six relatives do not recognize, ten meters away from male and female do not distinguish, thirty meters outside the animal is not distinguished...
However, there is a widely circulated saying that may allow many myopic people to comfort themselves:
When myopia becomes presbyopia, you don't have to wear glasses!
Myopia and presbyopia, one can't see far, one can't see close. One positive and one negative, canceling each other out, seems to be very intuitive and common sense.
But is that really the case?
Myopic presbyopia cancels each other out?
Maybe when you look closer
"Old flower" is actually a popular saying, its professional name is called "old vision", which refers to a normal phenomenon that becomes more and more unable to see the nearby as we get older.
As we age, everyone will age to varying degrees, and none of them will be spared. It's just that everyone's age at which symptoms appear is different.
To understand presbyopia, we have to start with how our eyes work:
Our eyes, similar to a "projector" that can be adjusted near and far, see the image that we see, in fact, the light reflected by the object, through the lens formed on the retina to form a reflection.
The lens is one of the key parts.
The elastic lens changes its thickness with the distance of the object, so that the reflection falls exactly on the retina.
When we look closely, the lens thickens under the drive of the ciliary muscle, and we can see the object in front of us.
The lens adjusts to thicken before it can see the nearby object
Image source: Author's public account "Luo Tsuen Talks about Eyes"
This is the problem with presbyopia – the ciliary muscle regulation decreases, and the lens is difficult to thicken.
In this way, the projection will "lose focus" when looking closely, resulting in unclear vision (you can imagine the projector not focusing).
So when looking closer:
For people who are not nearsighted, it is nothing more than the need to wear a pair of reading glasses;
For myopic people, it will feel like taking off myopic glasses to see more clearly.
This is also why many elders take off their glasses when they read books and look at their mobile phones.
Image source: Stand Cool Helo
In this way, myopia does have an advantage – it usually appears later in presbyopia.
In a very fortunate case, if the degree is just offset, there is no need to wear glasses to see close.
But such beauty, for most people is only temporary:
Friends with mild myopia, with the further decline of the lens regulation, the old flower exceeds the degree of myopia, then the flower will still flower.
Friends with high myopia may never wait for the day when they "just offset".
Because the increase in presbyopia is limited, according to the general reading distance, even if the lens completely loses its regulatory power, the presbyopia degree is more than 300 degrees. People with high myopia, even if they are highly presbyopia, still can't see closely.
Looking up close, lucky enough to offset, that... Looking into the distance?
Myopic people are old
I still can't see clearly from a distance
Myopia and presbyopia, whether they can be completely counteracted, here we have to look at it from the principle of the whole eye.
If you want the projection of the object to fall clearly on the retina, in addition to the thickness of the lens, the length of the eyeball is also important (the projector will spend too far away). This distance is medically called the "eye axis".
Although the results are all unclear, presbyopia is a lens of poor elasticity, while myopia is a relatively long eye axis, they are completely different two problems.
Not myopic: when the lens relaxes, it can see clearly into the distance
Myopia: The lens relaxes, but the focus falls less on the retina
For a simple understanding, we can divide the working state of the eye into two extremes:
- Look close: the lens adjusts to thicken;
- Looking at the distance: The lens relaxes and the focus should fall just on the retina (yes, the eye does not need to work hard when looking far).
For myopic people, the problem is only looking at a distance:
The lens is relaxed, but because the eye axis is too long and the focus is not on the retina, this time you need glasses to help.
Myopia requires the wearing of myopic glasses
In order to let the focus of distant objects fall on the retina
For people with presbyopia, the problem is only in looking at the near place: the lens loses its elasticity, and the adjustment is not very moving, so it is impossible to see the near place.
The principles of myopia and presbyopia are completely different, and there is no real sense of "offsetting".
Regardless of whether there are old flowers or not, the myopic eye can not see clearly in the distance, or can not see clearly.
Myopic and old flower, what should I do?
In fact, myopia + presbyopia, a total of the following 3 situations:
- Degree of myopia = degree of presbyopia, the legendary lucky one. In this case, you don't need to wear glasses to see the near place, you only need to wear the original myopic glasses when looking at the distance;
- Myopia degree < presbyopia degree. In this case, reading glasses need to be worn to see close, and myopic glasses need to be worn to see at a distance;
- Myopia degree > presbyopia degree. In this case, it is necessary to wear a slightly lower myopic lens to look at the nearby place, and the original myopic mirror can be worn at a distance
Yes, myopia + reading requires at least one pair of glasses.
If you don't want to keep replacing two pairs of glasses, there are other ways: wear dual-beam lenses or progressive multifocal lenses.
(Left) dual-beam lenses: there are two degrees of looking far and near, but the middle dividing line is obvious;
(Right) Progressive multifocal lenses: there are various degrees of distance, and there is a gradient transition in the middle, and the appearance can not see the boundary
If you really don't want to wear glasses and want to solve the problem of myopia and presbyopia at the same time, you can also choose to do surgery similar to myopia correction, such as corneal laser and intraocular lens implantation.
In addition, there is good news: the FDA recently approved an eye drop to relieve the symptoms of presbyopia, which has been available in China for a long time.
If necessary, you can go to the ophthalmology clinic and ask your doctor to help prescribe it.
But like myopia, all means, whether it is glasses, drugs or surgery, can only improve the symptoms of presbyopia, there is no way to fundamentally reverse the process of presbyopia, there is no way to cure presbyopia.
With the development of medical treatment today, there are really no problems that can be "cured" in the true sense.
Presbyopia is a degeneration of eye function and is a normal phenomenon that everyone experiences.
What we can do, on the one hand, is to take advantage of the youth to go outdoors and try to be less myopic; on the other hand, to find that there are old flowers, and to equip ourselves and parents with reading glasses as soon as possible.
This article is co-authored by experts
This article is reproduced in the author's public account "Luo Quan Talks About Eyes"
Minor additions and modifications
This article is reviewed by experts
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