> ## 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 the 20-20-20 rule and does it work? > The 20-20-20 rule: every 20 minutes, look at something roughly 20 feet away for 20 seconds. It targets blink rate and focusing effort, the two biggest driv # What is the 20-20-20 rule and does it work? **By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-15 · 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 The 20-20-20 rule: every 20 minutes, look at something roughly 20 feet away for 20 seconds. It targets blink rate and focusing effort, the two biggest drivers of digital eye strain, not blue light. No trial has tested the protocol itself, but the underlying mechanism is well established, so it is a reasonable, free habit. * 20-20-20 targets blink rate and sustained near focus, the two most consistent drivers of digital eye strain, not screen color. * No controlled trial has tested the 20-20-20 protocol itself; it's grounded in known physiology, not measured effect. * Blue-light lenses show minimal or no significant effect on contrast sensitivity or task performance versus standard lenses (Khorrami-Nejad, 2026). * Deliberate blinking, screen distance/height, glare reduction and full breaks address the actual causes more directly than any lens. * PROSPEK's clear lens measures 91.6% visible-light transmission (COLTS O-SPG111015) - near-clear, not a heavy filter. ## The rule in one sentence The 20-20-20 rule is a break schedule: every 20 minutes of screen work, look at something roughly 20 feet away for at least 20 seconds. The "20 feet" distance is meant to relax the eye's focusing muscles rather than provide a specific optical benefit, and the "20 seconds" is a rough floor, not a precisely studied threshold. It comes from clinical practice as a simple habit reminder, not from a single controlled trial that tested exactly those three numbers against each other. Sitting behind it is basic physiology: sustained close-range focusing and a lower blink rate are two of the most consistent contributors to digital eye strain, and looking at a distant object briefly reverses both. ## Why screens strain the eyes in the first place When someone reads a screen, blink rate typically drops well below the resting rate, which dries the tear film and leaves the eyes feeling gritty or heavy by the end of the day. Near-range text and small fonts also require sustained accommodative effort from the eye's focusing muscles, which is tiring on its own over several hours. Glare from overhead lighting or a bright window behind the monitor adds squinting and pupil adjustment on top of that. Posture compounds all of it: a screen positioned too high, too low, or too close changes head and neck angle in ways that also change eye strain. None of these four causes — blink rate, focusing effort, glare, posture — has anything to do with the color spectrum of the light coming off the screen. That distinction matters, because "blue light" is the explanation most often reached for, and it is the one with the weakest direct support. ## What the evidence says about the 20-20-20 rule itself No controlled trial in the record we rely on tests the 20-20-20 rule head-to-head against no breaks or against a different interval, so it is fair to call this a plausible, physiologically grounded habit rather than a proven protocol with a measured effect size. What is better supported is the underlying mechanism: reduced blink rate and sustained near focus are established drivers of eye strain, and a scheduled distance-glance break is a reasonable, free, zero-risk way to interrupt both. A meta-analysis of blue-light-filtering lenses (Khorrami-Nejad, Naroo, Oklla, Narooie-Noori, Therapeutic Advances in Ophthalmology, Jan 2026) found minimal or no significant difference in contrast sensitivity, color discrimination or task performance versus standard lenses, and describes efficacy for eye strain and circadian/sleep outcomes as still debated. That is a lens-specific finding, not a finding about breaks, but it points the same direction: symptom outcomes hinge more on behavior during screen time than on what is filtering the light. ## Where blue light fits, and where it does not A commercially available blue-light-filtering lens can measurably cut calculated blue-light hazard — one study found roughly a 10-24% reduction (Leung, Li & Kee, PLOS ONE, 2017) — but a hazard calculation is not the same as a change in symptoms. Our own clear lens (COLTS Laboratories report O-SPG111015, ISO/IEC 17025-accredited via A2LA) filters 99.99% of light at 400 nm, dropping to 63.0% at 420 nm and 33.1% at 450 nm, with 91.6% overall visible-light transmission — meaning it stays close to optically clear rather than acting like a heavy tint. That falloff is normal: no clear lens filters the entire 400-500 nm band evenly. A ZENOX clear-lens sample we tested averaged only about 52% across that same band, which shows the same limit in a different product. None of that changes blink rate, focusing distance, glare, or posture — the four things actually driving most digital eye strain. ## What actually helps, and in what order to try it In rough order of how directly each addresses a known cause: * Blink reliably and deliberately during reading-heavy tasks — this is the single most direct counter to screen-related dryness. * Take a 20-20-20 style break every 20-30 minutes; the exact interval matters less than doing it consistently. * Move the screen 20-28 inches away and set the top of the screen at or slightly below eye level, which reduces both focusing effort and neck strain. * Cut glare by repositioning the screen relative to windows and overhead lights, and increase text size before reaching for a magnifier of any kind. * Use lubricating eye drops for dryness that breaks alone don't resolve; that decision belongs to the wearer and an eye care professional, not a lens. * Keep room humidity reasonable and take full breaks, walking away rather than just glancing away, during long work blocks. ## Where a lens fits in this picture A tinted or coated lens is a small, situational piece of this picture, not a starting point. If a wearer already finds a slight tint more comfortable under bright indoor lighting, PROSPEK's clear and yellow lenses are measured and documented (see our lab-results page) rather than sold on an unqualified percentage claim. The yellow lens, for example, filters 98% of the 400-500 nm blue band and about 98.3% at the 460-480 nm band specifically, at roughly 65% visible-light transmission — enough tint to be noticeable, unlike the near-clear, 91.6%-transmission clear lens. ANSI Z80.3 testing on the clear lens group confirmed pass results for transmittance and color in COLTS report O-SPG111015. That standard governs light transmittance and color, not eye-strain outcomes, so it should not be read as clinical validation of a symptom benefit. The habit changes above do more, for free, than any lens will. ## 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 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) * [Why do screens give some people headaches?](/answers/screen-headaches)