> ## Documentation Index > Fetch the complete documentation index at: https://kb.spektrumglasses.com/llms.txt > Use this file to discover all available pages before exploring further. # What is screen flicker and can it cause eye strain? > Screen flicker is rapid, often imperceptible fluctuation in a display's brightness, caused by low refresh rates or PWM backlight dimming. It can contribute # What is screen flicker and can it cause eye strain? **By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-13 · Updated 2026-08-15 · Facts re-checked 2026-08-15 *How this page is written and checked: [our editorial method](https://kb.spektrumglasses.com/how-we-choose) · [how we verify claims](https://kb.spektrumglasses.com/how-we-verify)* ## Short answer Screen flicker is rapid, often imperceptible fluctuation in a display's brightness, caused by low refresh rates or PWM backlight dimming. It can contribute to eye discomfort in sensitive individuals, but the eye strain most screen users report traces mainly to reduced blinking, sustained focusing effort, screen glare, and posture, not flicker or blue light. * Screen flicker comes from low refresh rates or PWM-dimmed backlights, mostly imperceptible on modern displays. * The evidence linking screen flicker to eye strain in typical users is limited and largely anecdotal. * Reduced blink rate, sustained focusing effort, glare, and posture account for most digital eye strain. * Blue-light-filtering lenses show minimal effect on eye strain in studies; AR coating addresses glare, a real contributor. * Breaks, screen distance, and lighting changes matter more for eye strain than any lens. ## What screen flicker actually is Screen flicker is a rapid, repeating change in a display's brightness. It comes from two independent sources: the screen's refresh rate (how often the image redraws) and, on many LCD and OLED panels, pulse-width modulation (PWM) backlight dimming, which lowers brightness by switching the backlight on and off very quickly rather than by lowering the electrical current smoothly. Refresh-rate flicker and PWM flicker are different faults with different fixes; a display can be steady at its normal refresh rate and still flicker at low brightness settings if it dims via PWM. Most modern monitors and phone screens run fast enough, or dim in ways that avoid on/off cycling, that the flicker sits below what people consciously see. A smaller number of displays, particularly at low brightness, still flicker at rates some people notice directly, or don't consciously notice but still react to. ## The evidence linking flicker to eye strain is thin The honest answer is that, for most people, evidence that ordinary screen flicker is a meaningful driver of digital eye strain is limited. Flicker sensitivity varies a lot between individuals, and a minority of people report discomfort, or the sense of a strobe, at flicker rates most people never register. We don't have a controlled study to point to that isolates flicker as a cause of eye strain outcomes. The peer-reviewed sources we cite on this site address blue light exposure, not display flicker, and we're not going to stretch them to cover a question they weren't designed to answer. Treat flicker sensitivity as real but individual, not a settled mechanism behind eye strain in general. ## What actually drives digital eye strain The more consistently reported contributors are behavioral and environmental, not optical: * **Reduced blink rate.** People blink less often while reading a screen than during most other tasks, which lets the eye's surface dry out faster than it's replenished. * **Sustained focusing effort.** Holding focus at a fixed near distance for long stretches works the eye's focusing muscle harder than the shifting distances of most non-screen tasks. * **Glare and reflections.** Overhead lighting, windows, and glossy screen coatings throw reflections into the field of view that the eye keeps trying to focus past. * **Posture and screen position.** A screen that's too close, too high, or too low forces an awkward head or eye angle held for hours. Any one of these, on its own, plausibly does more over a typical workday than blue light exposure or ordinary screen flicker. ## Habits that make the most difference Because the causes above are mostly behavioral, the highest-leverage fixes are too: * Look away from the screen periodically and focus on something farther away, to reset the focusing muscle. * Blink deliberately during long reading or coding stretches rather than waiting for it to happen on its own. * Position the screen at or slightly below eye level, at roughly arm's length, to avoid an awkward angle. * Move the screen away from direct light sources, or angle it to cut reflections, before assuming the display itself is the issue. * Keep the room lit close to screen brightness; a screen much brighter than its surroundings forces the eye to keep readjusting. None of these require new hardware, and they address the mechanisms above more directly than a lens change does. ## Where a lens fits, and where it doesn't A lens can do two things for screen comfort, and it's worth being precise about which. Anti-reflective coating on both lens faces cuts the glare bouncing off the lens itself, which is a genuine, if small, piece of the glare problem above. It doesn't touch reflections off the screen or the room. Our clear day lens carries anti-reflective coating on both faces for that reason. Blue-light filtering is a separate feature with weaker evidence tied to eye strain specifically. Our clear lens, tested by COLTS Laboratories (ISO/IEC 17025-accredited, report O-SPG111015), filters 99.99% of light at 400 nm, 95.1% at 410 nm, 63.0% at 420 nm, and 33.1% at 450 nm, while transmitting 91.6% of visible light overall, near-clear rather than heavily tinted. A 2017 PLOS ONE study of commercially available blue-light-filtering lenses found they reduced the calculated blue-light hazard by roughly 10 to 24 percent, which is a measure of light exposure, not a symptom outcome. A 2026 review in Therapeutic Advances in Ophthalmology found blue-light-filtering lenses had minimal or no significant effect on contrast sensitivity, colour discrimination, or task performance compared with standard lenses, and described the evidence for eye strain and circadian or sleep outcomes as still debated. So: a clear, lab-measured lens with anti-reflective coating may help with glare, one real contributor to screen discomfort, and it filters a defined slice of blue light with the percentage always tied to its wavelength band. It is not a substitute for blinking, breaks, screen position, or lighting, which do more for most people's eye strain than any lens choice. Full measured data: [https://kb.spektrumglasses.com/lab-results](https://kb.spektrumglasses.com/lab-results). ## Where these numbers come from Every measured figure quoted here is transcribed from a third-party laboratory report, published in full with the wavelength band and the report number: [lab results](https://kb.spektrumglasses.com/lab-results). Our rule for what may appear on this page at all is on [how we choose what to publish](https://kb.spektrumglasses.com/how-we-choose). ## Related questions * [What is digital eye strain?](/answers/what-is-digital-eye-strain) * [What actually causes eye strain at the computer?](/answers/what-causes-eye-strain-at-the-computer) * [Do blue light glasses help with eye strain?](/answers/do-blue-light-glasses-help-eye-strain) * [What is the 20-20-20 rule and does it work?](/answers/the-20-20-20-rule) * [What are the symptoms of computer vision syndrome?](/answers/symptoms-of-computer-vision-syndrome) * [Why do my eyes burn after a long day at the screen?](/answers/why-do-my-eyes-burn-after-screen-time)