--- source_url: "https://note.com/kuma_aidesigner/n/n0a4875b66845?hl=en" title: "5 Scientifically Proven Reasons Why E Ink Smartphones Are Better for Your Eyes｜kuma | Web Designer" mirrored_at: 2026-08-13T01:09:02.343Z host: note.com cited_in_42a: true mirror_canonical: "https://index.42a.ai/note.com/kuma_aidesigner/n/n0a4875b66845__q__hl_en" --- > **Original source:** https://note.com/kuma_aidesigner/n/n0a4875b66845?hl=en Hello, I'm Kuma🐻. As a designer for 15 years, I've spent over 10 hours a day staring at screens, and as a result, my eyes were a wreck💦. When an ophthalmologist told me, 'If you keep this up, you're in trouble,' I tried an E Ink smartphone as a last resort—and it changed my life. I wrote about that experience in another article, so please check it out if you're interested. In this article, I will thoroughly explain 'why E Ink is gentle on the eyes' based on scientific evidence. This is a must-read for those who are skeptical, wondering, 'Does E Ink really work?' or 'Isn't it just a placebo?' ## ⏬ Reason 1: No backlight and less blue light The biggest reason E Ink is gentle on the eyes is that the screen itself does not emit light. Standard smartphones (LCD/OLED) display images by shining a strong backlight from behind the screen. Smartphone backlights, in particular, use white LEDs, which contain a large amount of high-energy blue light. On the other hand, E Ink displays are reflective screens, also known as 'electronic paper.' Because they reflect ambient light like paper, the screen itself doesn't need to emit light in bright environments. In dark places, the built-in 'front light' illuminates the screen, but this follows the same principle as shining a desk lamp on paper. Furthermore, recent E Ink devices are equipped with a 'warm light mode' that allows you to adjust the color temperature, significantly reducing blue light. ### 💬 Why is blue light a problem? Blue light has a short wavelength and high energy, making it easy for it to reach the retina. At an experimental level, it has been confirmed that retinal cells exposed to blue light release harmful substances called 'reactive oxygen species (ROS).' If these ROS accumulate, they can damage the retina and potentially increase the risk of light-induced damage in the future. A joint study by the Harvard T.H. Chan School of Public Health and E Ink Corporation yielded the following results: > Compared to reading on an LCD screen, stress on retinal cells was reduced by up to one-third on E Ink devices (using warm light). In other words, because E Ink can display content with the minimum necessary light (and light with fewer blue components), it physically places less strain on the eyes. ## ⏬ Reason 2: No flickering Another important point is 'screen flicker.' Common smartphones, especially those with OLED displays, use a method called 'PWM dimming' to adjust brightness. This is a technique that controls brightness by rapidly blinking the screen (around 100–500Hz). While this speed is invisible to the human eye, the retina and pupils actually react to this blinking. Research suggests that viewing high-frequency flicker causes the pupils to rapidly contract and dilate repeatedly, which leads to excessive tension in the eye muscles. As a result, it can cause blurred vision, eye strain, headaches, and migraines💦 ### 💬 E Ink is fundamentally flicker-free On the other hand, E Ink displays are essentially flicker-free. Once the content is rendered, it is held as a static image, and rewriting only occurs when turning the page. Except during a refresh, there is no constant flickering. The front light also illuminates at a constant intensity, so there is almost no flickering caused by PWM dimming. Recent devices incorporate eye-friendly designs such as DC dimming or warm-toned LEDs even at low brightness levels. It can be said that the strain caused by flickering factors when viewing for long periods is overwhelmingly smaller with E Ink. ## ⏬ Reason 3: Less prone to dry eyes and fatigue "My eyes get dry when I look at my smartphone for a long time"—everyone has experienced this, right? 💦 Eye strain caused by looking at a display for a long time includes symptoms such as eye pain, heaviness, difficulty focusing, and dry eyes. In fact, there is an interesting study comparing whether E Ink or LCD/OLED causes less strain. ### 💬 2021 Randomized Controlled Trial In a 2021 study, 119 subjects were divided into four groups and asked to read for two hours: 1\. Reading on an OLED smartphone in a bright environment 2\. Reading on an E Ink smartphone in a bright environment 3\. Reading on an OLED smartphone in a dark environment 4\. Reading on an E Ink smartphone in a dark environment The results were clear. In the group that read on an OLED smartphone for two hours: \- Corneal tear stability (tear break-up time) was significantly reduced \- Tear volume decreased \- Eye redness increased \- Subjective symptoms of dry eye worsened \- The frequency of blinking increased over time (due to eye discomfort) On the other hand, in the group that read on an E Ink screen for two hours: \- No significant changes in tear stability or tear volume \- Redness and worsening of subjective symptoms were very minor The researchers concluded that "reading on an OLED smartphone worsens the condition of the cornea and conjunctiva and causes clear discomfort, whereas E Ink screens minimize damage to the surface of the eye." ### 💬 Why is E Ink less tiring? The background to this is that, as mentioned earlier, E Ink has less direct light and blue light, making it easier to maintain natural blinking while reading. Furthermore, because the screen is static and does not flicker, it is believed that there is less strain on the eye muscles and the focusing system. In fact, another study (2013) had participants read for long periods using an E Ink device (Kindle Paperwhite), an LCD tablet (Kindle Fire HD), and a paper book, and the results showed that the LCD tablet caused the most significant decrease in blinking (= more prone to dryness) and the strongest reports of visual fatigue. There was no significant difference in fatigue levels between the E Ink device and the paper book, and both performed well. In other words, E Ink makes it easier to maintain a level of comfort close to that of paper, even during long reading sessions. ## ⏬ Reason 4: Protecting Sleep Quality "If you look at your smartphone before going to bed, you won't be able to sleep"—we've all experienced this, haven't we? Blue light from displays is deeply involved in this phenomenon. When the human brain is exposed to blue-to-green light (especially around the 460–480nm wavelength), it determines that "it is currently daytime" and suppresses the secretion of melatonin, a sleep hormone. ### 💬 The Impact of Tablet Reading Before Bed Medical experiments have compared reading on a backlit e-book device (tablet) before bed versus reading a paper book. Results: \- Those who read on a tablet experienced longer sleep latency (time to fall asleep) \- Reduced nighttime melatonin secretion \- Delayed internal body clock \- Negative impact on next-morning alertness and attention In short, looking at a bright backlit screen at night shifts your internal clock backward and lowers the quality of your sleep. ### 💬 E Ink Is the Same as a Paper Book On the other hand, since E Ink itself does not emit light, it is believed that if the conditions are similar to reading a paper book in a lit room, there is little negative impact on sleep. In the aforementioned experiment, reading a paper book did not cause melatonin suppression compared to tablet reading, and no negative impact on sleep was observed. Because E Ink devices can be read using reflected light just like paper, if you use appropriate indoor lighting without the front light, they are just as sleep-friendly as paper books. While recent E Ink readers come with front lights, using a warm-toned light (low color temperature orange light) can significantly reduce blue light. A joint study by the Harvard T.H. Chan School of Public Health and E Ink Corporation reported that using an E Ink device with a warm front light caused less retinal stress than using an LCD in night mode (adjusting the screen to a warmer tone). To put it extremely, if you turn off the front light on an E Ink device completely, there is zero blue light, so reading an E Ink device under a desk lamp before bed is almost the same situation as "reading a paper book before bed." When it comes to pre-sleep usage, E Ink displays are overwhelmingly superior to backlit displays. ## ⏬ Reason 5: Potential to reduce the risk of long-term eye diseases So far, we have looked at short-term effects like "less fatigue" and "easier to fall asleep," but what about the long term? The connection to eye diseases such as intraocular pressure, glaucoma, and cataracts is also a concern. ### 💬 Impact on intraocular pressure Intraocular pressure (IOP) is known as a risk factor for glaucoma, and it has been pointed out that the act of looking at a screen in your hand, such as a smartphone, may affect IOP. In a 2019 study, when subjects were asked to watch videos on a smartphone for 30 minutes and their IOP was measured, the average IOP rose significantly from 10.6 mmHg before the start to about 11.6 mmHg after viewing (an increase of about 1 mmHg, or approximately 10%). Furthermore, another study targeting patients with normal-tension glaucoma reported that even just using a smartphone for 5 minutes in a dim environment (100 lux) caused IOP to rise by about 11%, and a significant increase of about 30% occurred after 25 minutes of use 💦 While this is a transient change, it can be a burden for people with glaucoma or those with risk factors. Unfortunately, there is no direct data comparing IOP fluctuations between E Ink devices and LCD/OLED screens. However, in principle, since you are still staring at a screen at close range with E Ink, it is thought that some degree of IOP change could occur. Nevertheless, if E Ink users tend to read in bright environments like paper books, the risk of increased IOP might be reduced, unlike in dark environments where the pupils are dilated. Important point: At present, there is no established medical evidence that "looking at a smartphone screen" is a direct risk factor for developing glaucoma. The Glaucoma Foundation also states that "long-term screen use itself is not currently considered a risk factor for glaucoma." However, it is recommended to refrain from using smartphones at night, to avoid making the screen too dark and to properly illuminate the room if you must use it, and to avoid looking at it continuously for long periods. ### 💬 Impact on cataracts Cataracts are a disease in which the lens becomes cloudy, and while aging is the main cause, various risk factors such as ultraviolet rays, smoking, and diabetes are known. In recent years, there has been concern that "light emitted from digital devices (especially blue light) might accelerate the progression of cataracts." Since blue light can reach not only the retina but also the lens, it has been pointed out that long-term exposure may cause oxidative stress to the proteins in the lens, potentially promoting denaturation and aggregation. However, at present, there is a lack of clear scientific evidence that the level of blue light from smartphone or PC screens significantly accelerates cataracts. Many related studies are animal or cell experiments involving exposure to intense light, which are extreme conditions far removed from daily screen use. Nevertheless, since blue light exposure from digital devices is not zero when accumulated over many years, the stance is that it is desirable to reduce it if possible. In this regard, E Ink displays emit very little blue light, so even if blue light is involved in cataracts, it is possible that the risk could be kept low. The aforementioned study by Harvard University and E Ink points out that "bright white paper has a high blue light reflection component due to fluorescent whitening agents, whereas E Ink panels lack this and have lower blue light reflection," even stating that E Ink displays are actually safer and have less blue light reflection than paper. ### 💬 Impact on Macular Degeneration Age-related macular degeneration (AMD) is an age-related degenerative disease that occurs in the macula of the retina, and the possibility that blue light exposure may be a risk factor is being investigated in some circles. While the accumulation of oxidative stress in the retina due to blue light is the theoretical basis, there is no clear evidence that AMD is directly induced by normal screen usage. Nevertheless, long-term light stress can accumulate damage to the fundus, so the aforementioned research results regarding ROS production (the pace of ROS accumulation in retinal cells is 2-3 times slower with E Ink than with LCD) suggest that E Ink is gentler on the retina in the long term. ## ⏬ Conclusion: E Ink is Scientifically "Gentle on the Eyes" As we have seen so far, the hypothesis that E Ink displays are gentler on the eyes than backlit LCD/OLED displays is generally supported by science. The advantages are particularly clear in the following points: 1\. No light emission/less blue light → Up to one-third the oxidative stress on the retina. 2. No flickering → Prevents excessive tension in eye muscles. 3. Less prone to dry eye and fatigue → Tear stability is maintained even after 2 hours of reading. 4. Protects sleep quality → Does not interfere with melatonin secretion. 5. Potential to reduce long-term disease risk → Reduced risk of glaucoma, cataracts, and macular degeneration. However, it is not a panacea. It is not currently clear whether it is directly linked to disease risks such as glaucoma or cataracts, and the fact remains that, regardless of the type of display, long-term close-up work itself puts a strain on the eyes. Ultimately, proper usage (ensuring ambient light, taking breaks, posture, etc.) is important for maintaining eye health. ## 🌸 Summary: A Push for Your Next Step Thank you for reading this far! I would be happy if this made you think, "Maybe I'll try an E Ink smartphone." ✨ Of course, E Ink is not a cure-all. Any screen will strain your eyes if you stare at it for a long time. But at least being able to choose a "gentle option for your eyes" based on scientific evidence is reassuring for desk workers and gadget lovers, isn't it? I personally found that my eye fatigue improved dramatically after switching to an E Ink smartphone. I have written about that experience in detail, so please take a look. Thank you for reading! Please leave your opinions and thoughts in the comments below. Likes 💖 are also very encouraging!