Eye strain from screens: what causes it and how to reduce it

Published in July 2016, revised in 2026. The original explainer on the layers of an LCD screen still holds, but ten years of hardware and software have changed quite a few of the answers.

If you work at a computer, you probably know that end-of-day feeling: stinging eyes, sometimes a headache. In 2016, I wrote that the main cause was the monitor itself. That is still true, but we understand why better now, and we have far better tools to protect ourselves from it.

What lies behind the panel

A typical LCD screen is a sandwich of about six layers: a polarizing filter, a front electrode, the liquid crystals, a back electrode, a second polarizing filter, then the light source behind the whole stack. The point that matters: the liquid crystals emit no light of their own. They simply let through or block the light of the backlight, a sheet of LEDs that lights the panel continuously. When you look at an LCD screen, you are staring at a lamp, eight hours a day.

Each pixel is made of three sub-pixels, one red, one green and one blue. With 256 levels per channel, you get roughly 16.7 million colours. A small aside kept from the original post: Sharp's AQUOS range added a fourth, yellow sub-pixel.

Blue light, without the panic

Visible light is a wave, and the short wavelengths, on the blue and blue-violet side, are the most energetic in the visible spectrum. In 2016, I passed on some fairly alarmist sources about retinal toxicity and macular degeneration. Ten years later, I am walking that back: at the doses a screen emits, those risks remain debated. What is solidly established, on the other hand, is the effect on the circadian rhythm. Exposure to blue light in the evening delays melatonin production and degrades sleep. Glare and visual discomfort, for their part, are very real in every case.

Flicker, the quiet culprit

In the original post, I mentioned a stroboscopic effect tied to fluctuations in light intensity, invisible to the naked eye. That phenomenon has a name: PWM, for pulse width modulation. To lower brightness, many screens do not dim the source, they switch it on and off hundreds or thousands of times per second. The lower the brightness setting, the longer the off phases. You see nothing, but some eyes, and some brains, pay for it by the end of the day.

This is something to check even on OLED panels, which have otherwise solved the backlight problem since each pixel emits its own light. Many OLED screens, especially on mobile, modulate their brightness with PWM at frequencies that are sometimes low. If you are sensitive to it, look for flicker-free or DC dimming in the spec sheets.

Refresh rate matters too. Going from 60 to 120 Hz does not change the light emitted, but scrolling becomes crisper and the eye follows motion with less effort.

What has changed since 2016

Back then, I recommended f.lux, a small program that warmed up the display's colours in the evening. You had to install it yourself. Today it is all built in: Night light on Windows, Night Shift on macOS and iOS, an equivalent on Android. Turn on the sunset schedule and forget about it.

The other big step forward is system-wide dark modes. Windows, macOS, Android and iOS all offer a global dark theme, and apps as well as websites can detect it. A dark background in a dimly lit room means less total light sent to your eyes and less harsh contrast between the screen and its surroundings.

As for filtering glasses, which I recommended in 2016 (around 35 euros at LDLC at the time), the studies on their effectiveness against eye strain are mixed. A blue-light filter coating on prescription lenses stays a comfortable option, but do not expect a miracle from it.

The habits that cost nothing

• Match your screen brightness to the room. A white background at full power in a dark room is the worst possible setting.
• The 20-20-20 rule: every 20 minutes, look at something 6 metres away for 20 seconds. Your eye muscles finally release their focus.
• Blink. In front of a screen, your blink rate drops and the eye dries out.
• Increase the text size instead of leaning towards the screen.

The developer's part

Reducing visual fatigue is not only a matter of user settings, it is also the responsibility of whoever builds the site. Here, the dark theme is the default, a deliberate identity choice, but a light/dark toggle is available and your preference is remembered, then applied before the first render to avoid the white flash on load. The site also respects prefers-reduced-motion from end to end: if your system asks to reduce animations, the CSS cuts them and every JavaScript effect, parallax and transitions included, fades away.

This is basic ergonomics, not a gimmick. A site that tires its visitors makes them leave before they have even read the offer. It is the kind of detail I take care of in my development services and my maintenance plans. And if your eyes ache while reading your own site, let's talk.