When I was young, I had good eyesight. Will you be presbyopia when you are old?

There is a saying that people who are nearsighted will not have presbyopia. Is that so?

What is myopia?

Myopia is characterized by blurred vision and clear vision. In the absence of other adjustments, parallel light from a distance enters the eye through the pupil, and the focus is in front of the retina, which cannot form a clear object image on the retina. This is myopia.

Presbyopia looks like hyperopia.

Presbyopia, also known as presbyopia, may be caused by the word "old". Everyone thinks that this is a problem only for the elderly. In fact, it appeared earlier than everyone thought. After the age of 30, most people will start presbyopia. Myopia is mostly caused by abnormal anterior and posterior diameter of eyeball, while presbyopia means that the elasticity of lens deteriorates with age, and the ciliary muscle can't relax no matter how tense it is; Or the ciliary muscle itself is aging, which is a phenomenon of aging human function. It tells you that your eyes are aging.

If you get myopia, won't you get old?

Presbyopia, as a normal physiological phenomenon, happens to everyone at the corresponding age. It's just that people who were nearsighted used to wear short-sighted glasses (concave lenses) to correct them. When they reach the age of presbyopia, their eye accommodation decreases, and the presbyopia degree offsets part of the myopia degree (equivalent to adding a convex lens to a concave lens), so it will happen that they take off their glasses to see the nearby objects more clearly. For example, there used to be myopia of 65,438+000 degrees, but at presbyopia age, presbyopia of 65,438+000 degrees appeared, so you can see clearly with your eyes at close range without glasses, which will give people the illusion that you don't have presbyopia, but it is not.

Presbyopia does not mean farsightedness.

Hyperopia is because the curvature of cornea and lens is too small or eyeball is too short, and the light finally focuses on the back of retina, so you can't see clearly. Presbyopia, on the other hand, reduces the adjustment ability when looking at different objects near and far, resulting in unclear vision. Hyperopia and presbyopia seem to be corrected in the same way, but they are not the same thing. Hyperopia mostly occurs in children, while presbyopia generally occurs in middle-aged and elderly people. The degree of correction increases year by year with the increase of age, and because of the decline of adjustment ability, even if the degree is not high, objects close to a certain distance can not see clearly through their own adjustment, and must move farther away.

Presbyopia is irreversible. People who have better eyesight when they are young tend to have presbyopia earlier and have more obvious symptoms. Therefore, when they are nearsighted and tired, they should go to the ophthalmology department of a professional hospital for presbyopia fitting.

This work is the original of "Popular Science China-A Brief Introduction to Scientific Principles", please indicate the source for reprinting.