What happened to those who often turned off the lights to look at their phones? You would never have thought of these 4 changes

Patients who come to the clinic often have red bloodshot eyes. When asked, they say they stayed up late playing with their phones. In fact, everyone knows that playing with mobile phones after turning off the lights is bad for the eyes, but the specific harm is not clear, which leads to many people not fully aware of the harm and always want to play.

So, what effects does frequently turning off the lights to look at your phone have on your body? And how can you play more healthily?

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Often turn off the lights to check the phone

There are 4 possible hazards to the eyes

Let’s first take a look at what bad effects playing with mobile phones when turning off the lights has on the eyes.

1. Temporary blurring of vision

The main manifestation is that after playing with the mobile phone for a long time in the dark, one eye can see things, but the other eye can't see clearly temporarily, and it takes a few minutes to recover. This is mainly related to the habit of using the mobile phone and the dark adaptation of the human eye.

When using a mobile phone at night, many people are used to lying on their side and using one eye to see. If the room is dark and the lights are off, and the mobile phone screen is suddenly turned off, in a dark environment, you may find that the eye that was previously looking at the mobile phone can no longer see, but the other eye can. In fact, this is the dark adaptation of the human eye. Normally, when we walk from a bright place to a dark place, we will also have this feeling, and it takes some time to adapt before we can gradually see things in the dark.

This is because our eyes have two types of photoreceptors: cones and rods. Under strong light stimulation, cones can immediately start working, so when we go from dark to bright, although we feel glare, we can see objects clearly in an instant. This process is called light adaptation. In dark environments, rods come into play, and they need a certain amount of adaptation time before they can start working.

In addition to dark adaptation, there are also literature reports that playing with mobile phones in dim light for a long time may have some effects on photoreceptor cells, resulting in decreased vision. However, it is basically reversible, and the visual function of the eyes can be restored after a period of time.

2. Cause dry eyes and visual fatigue

Studies have shown that many people may experience symptoms of visual fatigue such as blurred vision, eye swelling, and eye pain after using a computer for an hour, and the severity of visual fatigue is significantly related to the time spent using the video terminal. Mobile phone screens are smaller than computer screens and require closer viewing distances, so the eye burden is heavier and visual fatigue is more likely to occur.

Healthy eyes always look black and white. The black part of the eyeball is not completely black. The surface is the colorless and transparent cornea, and the iris underneath is dark brown, like most Chinese people. The white part of the eyeball is the sclera, and there is a thin layer of tissue on the surface of the sclera called the conjunctiva.

Normally, the blood vessels on the conjunctiva are in a "dormant" state and cannot be seen by us. Once there is an infection or other stimuli, the "dormant" blood vessels will expand and become congested, accelerating metabolism, which is what we can see as red bloodshot. If your eyes turn red after staying up late, it is actually your eyes reminding you that it is very tired and needs to rest.

There is a layer of structure on the surface of the eyeball called tear film, which mainly plays the role of moisturizing the cornea. Staring at the mobile phone screen for a long time will cause the eyes to involuntarily reduce the frequency of blinking, resulting in more tear evaporation and decreased stability of the tear film, which can easily lead to symptoms of dry eyes and visual fatigue such as dry eyes, soreness and swelling.

3. Causes the occurrence and development of myopia

As we all know, for children, too much close-up use of the eyes can cause ciliary muscle fatigue, thereby increasing the possibility of myopia. But in fact, too much close-up use of the eyes by adults can also lead to an increase in myopia.

Especially at night, if you lie on your side and look at your phone, using only one eye for a long time, the myopia of this eye may develop faster, causing a large difference in the degree of the two eyes, further affecting binocular vision function.

4. Causes angle-closure glaucoma

Glaucoma is an irreversible blinding eye disease, mainly due to excessive intraocular pressure that exceeds the tolerance of the eyeball, causing damage to the optic nerve. Clinically, the normal intraocular pressure range is defined as 10mmHg~21mmHg, and the stability of intraocular pressure mainly depends on the circulation of aqueous humor in the eyeball.

When you turn off the lights and play with your phone in a dim environment, your pupils will become larger. For people with special eyeball structures, such as small eyeballs and narrow chamber angles, this may affect the circulation of aqueous humor, causing a sudden increase in intraocular pressure and leading to an acute attack of glaucoma. When an attack occurs, not only will you have eye pain and headaches, but it may also cause irreversible damage to your vision.

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Playing with mobile phone at night

Are eye protection mode and night mode useful?

The eye protection mode of the mobile phone mainly protects the eyes from the perspective of anti-blue light. Blue light itself exists in sunlight, and the LED lights, LCD monitors and mobile phone screens in daily life all release blue light.

According to the wavelength, blue light can be divided into shorter wavelength blue light (400 to 440 nanometers) and longer wavelength blue light (440 to 500 nanometers). It is generally believed that shorter wavelength blue light has high energy and may cause damage to the fundus, while longer wavelength blue light is good for our dark vision and circadian rhythm.

The peak spectrum of the LED light sources we use in daily life is mostly between 450 and 500 nanometers. As for the illumination of mobile phone screens, there is usually no need to worry about damage to the fundus.

The night mode of a mobile phone usually sets the screen brightness to adjust accordingly with the brightness of the ambient light. For example, if the room is dark, the brightness of the mobile phone screen will also dim. In theory, it will relax people's nerves and gradually transition to a sleep state.

But as mentioned before, this kind of dim light is not very friendly to the eyes. Therefore, it is not really feasible to use your phone at night just relying on eye protection/night mode.

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Do these 3 things when browsing your phone

More friendly to the eyes

It is a habit for many people to check their mobile phones before going to bed. It is basically difficult to quit it completely. However, paying attention to the following points can reduce the damage to the eyes to a certain extent.

1. Adjust ambient light

If you must check your phone before going to bed, it would be better to turn on a reading light or a night light in the room so that the contrast between the surrounding environment and the screen brightness is not too great.

2. Pay attention to your eye posture

It is better not to play while lying down, sitting is better. The distance between your eyes and the phone should not be too close, a relatively far distance that is comfortable for you is better. If you must play while lying down, do not lie on your side, and keep both eyes at the same distance from the screen.

3. Control the time you spend using your eyes

It is better to play less than anything else, but if you really can't do it, then increase the rest intervals. You can use the 20-20-20 principle to rest, which means using your eyes for 20 minutes, at least 20 seconds, you can close your eyes or look into the distance.

Finally, when you wake up in the morning and look in the mirror and see that your eyes are red, or if you feel dry, sore eyes, or other discomfort, you should pay attention to it. Your eyes are overloaded and need to be adjusted.

Planning and production

Author: You Yuxia, deputy chief physician, Beijing Aier Xinli Ophthalmology Clinic, doctor of medicine

Reviewer: Liu Gang, deputy chief physician of ophthalmology, Qilu Hospital, Shandong University, Qingdao Branch