If you are nearsighted, you won’t have presbyopia? Don’t be naive!

Author: Yan Xin, resident physician at Beijing Tongren Hospital, Capital Medical University

Reviewer: Tian Bei, Chief Physician and Professor, Beijing Tongren Hospital, Capital Medical University

We often say that "eyes are windows to the soul", but have you ever thought that this window will also "age". Many older people will encounter a problem: it becomes increasingly difficult to see close objects, which is the so-called "presbyopia". But many people have heard of this saying - "If you have myopia, you won't have presbyopia", is this true? Today, let's talk about things about eyes.

How do the eyes “focus”?

Think of your eye as a super-sophisticated camera:

The cornea, aqueous humor, lens, and vitreous body are like the lens of a camera, responsible for focusing light.

The retina is like the film in a camera, receiving and recording images.

The lens is the focuser of this "camera". When you look at something close, it becomes more convex, so that the focusing ability is stronger; when you look at something far away, the lens becomes flat and the focusing ability is weakened. With the help of this "focuser", we can see clearly both far and near.

Figure 1 Original copyright image, no permission to reprint

What is refractive error?

Refractive error, in simple terms, means that you can't see clearly. When the eyes are relaxed, parallel light rays cannot focus on the retina after passing through the eye's refractive system, and thus cannot produce a clear image, just like the focal length of a camera and the position of the film are not aligned. There are three main situations:

Myopia: The focus of light falls on the retina, and distant objects appear blurry.

Hyperopia: Light rays focus behind the retina, making nearby objects appear blurry.

Astigmatism: Light forms several focal points on the retina, causing objects to appear distorted and blurry.

Figure 2 Original copyright image, no permission to reprint

What about presbyopia?

Presbyopia is more commonly known as old eyes. As we age, the lens gradually loses its elasticity, the eye's ability to adjust becomes worse, and it becomes difficult to see close objects. Generally, people start to feel it at the age of 40 to 45. Although both presbyopia and refractive error affect vision, it is not refractive error, but a normal physiological phenomenon. Basically, everyone will have presbyopia when they reach middle age or old age, but the time and degree are different. It's like a camera that can focus becomes a fixed-focus camera.

Nowadays, electronic products are used more frequently, and some young people have also developed symptoms of presbyopia. In fact, people's accommodation ability decreases by 0.3D every year since birth. According to research, the relationship between accommodation ability and age is as follows:

Minimum adjustment range (D) = 15 - 0.25✖age

Average accommodation amplitude (D) = 18.5 - 0.3 ✖ Age

Maximum adjustment range (D) = 25 - 0.4 ✖Age

I won’t have presbyopia if I’m nearsighted? Don’t be misled!

Many people think that people with myopia will not have presbyopia, which is totally wrong. Myopia and presbyopia are two completely different things:

Myopia: It is because the eye axis becomes longer, and the light cannot be accurately focused on the retina, so distant vision is blurred.

Presbyopia: This is because the lens has lost its elasticity and cannot adjust the focus, so close objects are blurry.

Simply put, myopia is a "natural focal problem" while presbyopia is "the lens can't focus due to age."

Look at the picture below. The two people are about the same age and have about the same accommodation power. The one below is a myopic patient. When looking at distant objects, the myopic patient's focus is in front of the retina, so he can't see clearly. But when the two look at nearby objects at the same time, because the accommodation power decreases, the myopic patient has a stronger refractive power, and the focus falls exactly on the retina, so the vision is clear; while the emmetropia has insufficient accommodation power, and the focus falls behind the retina, so the vision is blurry. This is presbyopia.

Figure 3 Original copyright image, no permission to reprint

Some people also say, "I have worn glasses before, and wearing glasses gives me normal vision, and I can see closer than my peers, so I won't have presbyopia, right?" In fact, this is mostly because your myopia has not been fully corrected. It used to be said that myopia would stabilize after adulthood, and many people were affected by this and didn't change their glasses for a long time. Nowadays, most jobs require close-up use of the eyes, and many people don't realize that they can no longer see clearly at a distance. In addition, with the popularity of electronic products and increased use of the eyes at close range, myopia in adults may also worsen. The latest research found that for people aged 20 to 50, the average myopia degree increases by about -1.00D, and the situation is more serious for people with high myopia. Therefore, if these people get a pair of glasses with the right degree, presbyopia symptoms will appear.

How to protect our eyes?

Presbyopia is a normal physiological phenomenon, but increasing myopia is not. Therefore, adults also need to pay attention to protecting their eyes. In addition to reducing the time spent using electronic products, they should also increase outdoor activities to protect the windows of our souls.

Reduce the time spent using electronic products: After every 20 minutes of using your eyes, remember to take a 20-second break and look into the distance to relax your eyes.

Increase outdoor activities: Outdoor light helps maintain eye health and prevent myopia from worsening.

Check your eyesight regularly: Especially for people over 40 years old, have regular eye examinations and wear appropriate glasses in time.