Is there such a thing as *good* screen time?

Excessive “screen time”—that is, time spent exposed to digital devices like smartphones and tablets—has been shown to cause eye strain and have a detrimental impact sleep patterns as well as mental and physical health in a variety of ways. But does that mean you need to banish all screens from your life to improve your health?

Which screen do you mean? LED vs. E Ink

Most studies on the effects of screen use focus on LED screens. These are the screens in our smartphones, tablets and computers—and just about everywhere we see digital images. LED screens produce vibrant colours and are great for watching any kind of content. But they need to continuously produce their own illumination to be seen.

E Ink is a screen technology that's often used in place of paper, whether in store signs and shelf tags or book-like devices such as eReaders.

Understanding how different screen technologies work with our eyes can help illuminate which screen time is harmful and which might actually be helpful.

LED screens: phones, tablets, computers

“Digital eye strain” and “computer vision syndrome” are by now familiar conditions caused by extended use of tablets, computers, and smartphones. With illumination provided by light-emitting diodes (LEDs) the screens of these devices are emissive, meaning they’re made visible by shining light at your eyes. When you’re outdoors or in another brightly lit space, those lights need to shine even brighter to make the screen visible.

The screens of tablets are emissive, meaning they’re made visible by shining light at your eyes

Studies have observed a lowered blinking rate among users looking at emissive digital devices, leading to dry eyes and feelings of eye strain. Among children, the effect of excessive exposure to computers and tablets can lead to conditions that impair the eyes’ ability to track across a page, making reading difficult. For this reason, exposure to LED screens in tablets, smartphones, and computers should be limited for all users, but especially children.

E Ink screens: eReaders

E Ink is a non-emissive screen technology commonly used in eReaders. An E Ink screen consists of an array of tiny black and white ink particles that physically move in response to an electric charge: as you “turn the pages” of an eBook, the eReader re-arranges these particles in a fraction of a second, like a printer applying ink droplets onto a sheet of paper.

If you're comfortable reading a printed page, then it's unlikely you'd experience any eye strain reading on an eReader. That's because with an eReader, every page you turn is physically “printed” in E Ink the moment you’re ready to read it. And since the screen itself doesn’t produce light to be seen, viewing an E Ink screen is like viewing any other object, such as the printed page of a book.

If you're comfortable reading a printed page, then it's unlikely you'd experience any eye strain reading on an eReader

Lacking a built-in need for illumination, many eReaders come equipped with different kinds of “front-lighting” to enable reading in dark rooms. Just like a book lamp, front-lighting bounces light off the “page” to make it visible in the dark. If you’ve ever clamped a book lamp to your book, front-lighting is similar but scaled down to fit inside the edges of an eReader’s screen.

Blue light, eye health, and sleep

Most of the light emitted by LEDs—the light source behind phones tablets and computers—comes from blue light, the part of the light spectrum with the shortest wavelengths and highest energy. Exposure to blue light has been shown to decrease the ability of cells in the eye to repair themselves, raising concerns of vision impairment especially in children.

Additionally, while the sleep-regulating hormone melatonin is impacted by any kind of light, research has shown blue light to have a significantly more powerful effect than light from other parts of the spectrum. Because interfering with our natural sleep cycles can lead to an increased risk of health conditions including diabetes, heart disease, and depression we need to be careful about our exposure to night-time illumination.

Exposure to blue light has been shown to decrease the ability of cells in the eye to repair themselves

“Night mode” settings can help reduce the level of blue light you’re exposed to later in the day on devices with both LED and E Ink screens. However, even when set to night mode tablets and smartphones still emit much more blue light than eReaders.

Impacts of screen use on mental health

Studies have shown that “smartphone addiction”—that is, frequent checking of a mobile device's LED screen—can lead to negative impacts on learning, memory, and mental health. It can even increase the risk of early-onset dementia by accelerating the normal loss of brain mass that happens as we age.

Experts recommend avoiding smartphones and tablets first thing in the morning, ideally for an hour or more after waking. Alternatives they suggest include journaling, reading books (not on a tablet or smartphone), or listening to music or audiobooks.

Conclusion: is there such a thing as good screen time?

As health experts continue to warn against an excess of screen time, more and more activities are moving into digital spaces that demand interactions with smartphones and tablets.

Fortunately, use of an eReader with E Ink screen does not appear to correlate with the negative health effects commonly associated with smartphones and computers. What’s more, reading has been shown to offer a variety of good health effects, ranging from benefits to brain function to helping you live a longer, less stressful life. ◼

Sources:

• Comparison of oxidative stress response of in vitro retinal cells exposed to blue light from emissive versus reflective displays - Wang - 2023 - Journal of the Society for Information Display - Wiley Online Library
• Effect of increased screen time on eyes during COVID-19 pandemic - PMC
• What Excessive Screen Time Does to the Adult Brain | Cognitive Enhancement
• Blue light has a dark side - Harvard Health
• What is Blue Light from Digital Devices? Is it harmful for eyes?
• Increased screen time leads to more eye strain and convergence insufficiency in children
• Computer Vision Syndrome: Symptoms, Treatment & Prevention