What is the 20-20-20 rule?
Coined by Californian optometrist Dr Jeffrey Anshel in the 1990s, the rule says: every 20 minutes of screen work, look at something 20 feet (about 6 metres) away for at least 20 seconds. The distance forces your ciliary muscles to relax (they are tonically contracted when focusing close) and triggers the natural blink rate, which drops by 60% during screen reading. The American Academy of Ophthalmology endorses the rule as a baseline intervention for digital eye strain, also called computer vision syndrome.
Does it actually work?
There is decent evidence it helps with symptoms — dryness, blurring, headaches — though not with longer-term effects like myopia progression. A 2022 study in Contact Lens & Anterior Eye showed regular 20-second distance breaks reduced reported eye strain by 23% over four weeks compared to controls. The mechanism is well understood: distance focus releases accommodation, blinking restores tear film, and pulling visual attention away from a single focal plane reduces strain on the extraocular muscles. The 20 feet figure is not magic — anything beyond about 4 metres triggers the same relaxation response.
What if I do not have a window or open space?
Any distance focus helps. Look at a corner of the ceiling, down a corridor, at a poster across the room, or close your eyes entirely for the 20 seconds — closing the eyes restores the tear film even without distance focus. The key is to break the close-range stare. If you work in a small room, leaving the screen and walking to a kitchen or hallway is the best break. Combining the break with standing up (see /utility/standing-desk) doubles the benefit.
Will this fix my eye strain on its own?
Probably not by itself. Eye strain has multiple causes: dry eyes, uncorrected refractive error, poor screen position, glare, and small text all stack on top of accommodation fatigue. The 20-20-20 rule addresses accommodation only. Combine it with: 50–70 cm viewing distance, screen top at or just below eye level, 60% relative humidity if possible, and an eye exam every 18 months. Blue-light glasses do not have strong evidence behind them — a 2023 Cochrane review found no measurable benefit for digital eye strain symptoms.
Can I customise the interval?
Yes — adjust above. Some people prefer 30-minute or 45-minute intervals because 20-minute pings interrupt deep work. The trade-off is that longer focus sessions cause more accommodation lock-up. A common compromise: 20-20-20 during heavy reading or coding, 45-45-45 during meetings where you blink more naturally. Pair this with a Pomodoro timer (/utility/pomodoro) — the 5-minute Pomodoro break is plenty of time for the 20-20-20 cue and a stretch.
Why is the audio cue so quiet?
Loud beeps trigger startle responses and elevate heart rate — the opposite of the calm break this is supposed to be. The cue is a half-second pure sine fade-in/fade-out at 440 Hz, audible without being jarring. If you cannot hear it, raise your system volume — and request browser notification permission for a visual prompt as well. Notifications work even when the tab is in the background, which audio mostly does not on mobile browsers.