Recently, a friend was planning to change his phone, so he asked me for recommendations on suitable LCD screen smartphones. I was quite surprised to learn that he is still a fan of LCD, considering that LCD screens are becoming less common these days and true “die-hard fans” are actually quite rare.
However, after asking him, I found out that he is not really a die-hard fan. The reason he prefers LCD is simple: he feels that his myopia has worsened, and he suspects it might be due to the OLED screen. He mentioned that he had no issues with his eyes when using an LCD screen, but ever since he switched to a new phone with an OLED screen last year, he feels that his myopia has worsened, so he wants to switch back.
To be honest, recommending a few smartphones is not a big deal, but the claim that OLED screens are harmful to the eyes is true. However, does that mean LCD screens are definitely better for the eyes? For people with myopia, that may not be the case. It’s important to remember that any electronic screen, whether LCD or OLED, can be harmful to the eyes. This is primarily due to blue light and flicker.
The Impact of Blue Light on Vision
As we all know, any electronic screen emits blue light, which refers to visible light with wavelengths between 380nm and 500nm. The term “visible light” means light that can be seen, and sunlight is a typical example of visible light, which also means that blue light is almost everywhere.
Is it surprising? We often hear that the light emitted by mobile phones and computer screens can be harmful, but how often have you heard that sunlight can be harmful? On the contrary, when people think of sunlight, they often associate it with vitality and health, and even sunbathing is considered a healthy lifestyle.
So why is it that blue light from phones is harmful to the eyes, while sunlight is not? This brings us to the classification of blue light.
In reality, different wavelengths of blue light affect the eyes differently. However, a certain type of shortwave blue light can harm the retina, threatening our eye health. The blue light emitted by mobile phones, tablets, computers, and televisions falls into this harmful shortwave category.
Diagram of the Human Eye Structure
For individuals with myopia, due to their natural sensitivity to bright light, the blue light emitted by electronic screens is generally brighter than other light sources, except for ultraviolet light. Since shortwave blue light has a shorter wavelength, it causes the retinal focal point to shift forward. Over time, during the repeated “tug-of-war” of the ciliary muscles, the muscles can lose elasticity, leading to eye fatigue or worsening myopia!
All of this information can be found online, but what many may not know is that between LCD and OLED screens, LCD emits shorter wavelengths of blue light. This means that if we purely discuss the harmful effects of blue light on the eyes, LCD actually poses a greater risk than OLED.
Isn’t that a bit of a cognitive shock? How can it be that LCD screens are not only not better for the eyes than OLED but actually worse? The truth is that there is another factor that affects the eyes: flicker. Unfortunately, OLED screens are particularly prone to flicker.
The Impact of Flicker on Vision
In the digital world, two terms are well-known: DC dimming and PWM dimming. Most LCD screens support DC dimming, while OLED screens use PWM dimming. The principle of DC dimming is straightforward: it changes the screen’s brightness by increasing or decreasing the power of the circuit. When the power increases, the screen gets brighter; when it decreases, the screen dims, and it features almost no flicker.
On the other hand, PWM dimming works differently. OLED screens do not emit light continuously; instead, they turn on and off rapidly. When the frequency reaches a certain level, the human eye perceives the screen as continuously lit.
However, sensitivity to flicker varies from person to person. This is why some people experience discomfort, headaches, eye fatigue, and dizziness when using the same OLED screen, while others do not.
Moreover, due to the self-emitting nature of OLED screens, when using the phone in low-light environments, the PWM dimming mechanism can only reduce brightness by adjusting the frequency of the screen’s “on” and “off” cycles.
In such cases, the flicker frequency becomes lower, and although the human eye may not easily detect it, it begins to exert pressure on vision over time, causing the ciliary muscles to constantly contract and relax, remaining in a tense state. Therefore, prolonged exposure to flicker can indeed lead to vision decline or worsening myopia.
How Should Myopic Individuals Choose Smartphones?
Without a doubt, both blue light and flicker can harm vision, and LCD screens are not necessarily better for the eyes than OLED. The misunderstanding arises primarily because LCD screens rarely cause discomfort, such as glaring or dryness, but fundamentally, both LCD and OLED screens are not very friendly to myopic eyes.
But can myopic individuals really avoid smartphones? Of course not. Given this, when purchasing a phone, one needs to pay extra attention.
As mentioned earlier, the blue light and flicker emitted by electronic screens can harm vision. Fortunately, smartphone manufacturers have not ignored this issue and have taken various measures. This is undoubtedly good news for myopic individuals.
Low Blue Light Certification from TüV Rheinland
For instance, in terms of blue light protection, it is common to see manufacturers promoting various eye care certifications in their phone marketing. Common certifications include the low blue light certification from TüV Rheinland and SGS screen eye protection certification. These certifications are not easily obtained by simply paying a fee; they adhere to a set of credible and authoritative testing standards. Products that pass these certifications gain recognition in the market, as well as in the eyes of users and manufacturers.
Currently, some mainstream smartphone brands have adopted relevant eye care certifications, such as OPPO, vivo, Honor, Xiaomi, and Samsung, among others. These certifications are common across flagship and budget models alike. While there may be some advertising involved, they still provide a degree of authoritative backing, making it relatively reliable and ensuring that users are not entirely blind in their choices.
Difference Between DC Dimming and PWM Dimming (Source: Internet)
As for flicker protection, current smartphone eye care measures are also quite effective. For LCD phones, many support DC dimming, which is a straightforward and efficient dimming method that is relatively friendly to vision. For myopic individuals, DC dimming can alleviate eye fatigue caused by prolonged smartphone use. If you are very sensitive to low-frequency PWM dimming, it is indeed advisable to choose this type. However, it is important to note that many LCD phones also incorporate PWM dimming modes, and some low-end LCD phones even use low-frequency PWM dimming, which can also be harmful to the eyes with prolonged use.
Of course, it is a fact that LCD phones are becoming increasingly rare, especially in the high-end product line where LCD is nearly extinct. In such cases, even if you prefer LCD, it may not be possible since only OLED options are available. Fortunately, while OLED cannot achieve pure dimming, there are products that support “pseudo DC dimming” and “high-frequency PWM” eye care technologies.
Honor 60 Series Supports High-Frequency PWM Dimming and TüV Rheinland’s Low Blue Light Certification
For example, the Honor 60 series triggers high-frequency PWM dimming when users operate their phones in low-light conditions, providing a comfortable screen experience and reducing color loss, ensuring that the phone maintains a low brightness level without significant flicker and preserves color accuracy for a more precise display.
Final Thoughts
For myopic individuals, there is no standard answer to which dimming method is better. It depends on the manufacturer’s proficiency in screen calibration. If the calibration is not well done, even the best eye care technologies may not be effective.
If you are genuinely concerned about eye safety, then smartphones with LCD screens that support blue light protection and DC dimming would indeed be a good choice. Most mainstream LCD phones should not have any issues, so you can choose with confidence. Of course, if you are not keen on LCD, opting for OLED screen phones is also acceptable, provided they support high-frequency PWM or pseudo DC dimming technologies. Regardless, having support is better than not having it at all.
