The 20-20-20 Rule
A one-line habit for screen-heavy work: every 20 minutes, look at something 20 feet away for 20 seconds. Here is where the number came from, what the evidence actually supports, and how to do it so it counts.
Updated · 9 min read
The rule in one line
Every 20 minutes of screen work, look at something at least 20 feet (about 6 metres) away for at least 20 seconds.
That is the whole thing. The rest of this page is about doing it correctly and knowing its limits. Use the free timer if you want the reminding handled for you.
Why looking away helps
Two things happen when you focus on a screen for a long stretch, and neither is about the screen emitting anything harmful.
Your focusing muscle stays contracted. To see something close, the ciliary muscle inside your eye changes the shape of the lens — a process called accommodation. Hold that contraction for hours and it behaves like any other held muscle: it gets tired. Looking at a distant object lets it release. That is why the distance matters and why glancing at your phone does not count.
You stop blinking properly. Blinking spreads the tear film across the cornea. During concentrated screen work, blink rate drops sharply and many blinks become incomplete — the upper lid does not fully close — so the surface dries out even when you are technically blinking. The result is the gritty, burning, watery feeling most people describe as tired eyes. A break is an opportunity to blink fully and slowly a few times.
The American Academy of Ophthalmology's guidance on computers, digital devices and eye strain leans on exactly these two mechanisms: make a conscious effort to blink, sit about an arm's length from the screen, gaze slightly downward, and match screen brightness to the room.
Where the rule came from
This is the part most articles skip, and it matters for how much weight you put on the number.
The rule was coined around 1991 by Jeffrey Anshel, OD, a California optometrist, while he was lecturing on relieving computer vision stress and writing his book Visual Ergonomics in the Workplace (published 1998). Before it, the standard advice was a 15-minute break every two hours. Anshel's patients were reporting headaches and focusing problems well inside two hours, so the interval was clearly too long.
He packaged it as the third of his "3Bs": Blink, Breathe, Break. 20-20-20 is the "Break" instruction made specific enough to follow.
You will see it written both as the 20-20-20 rule and as the 20 20 20 rule. They are the same habit; the spaced form is simply how most people type it into a search box.
The important detail: the numbers were borrowed, not derived. Anshel took research showing that shorter, more frequent breaks help with musculoskeletal disorders and mapped that pattern onto the visual system. It was a reasonable inference from ergonomics, not a finding from vision science.
We know this because optometrist Brian Chou, OD went looking for the origin and traced it through the California Optometric Association to Anshel himself, who confirmed it. Chou published the investigation in Optometry Times in February 2018, and noted that at that point "no peer-reviewed studies to date have validated, let alone evaluated this technique."
A rule can be sensible and widely recommended without having been tested. For about 27 years, this one was.
What the research actually shows
The most direct test so far is Talens-Estarelles et al., Contact Lens and Anterior Eye 2023;46(2):101744, run from Aston University with the University of Valencia. It is worth reading carefully rather than summarising as "science proves it works".
The researchers enrolled 29 computer users who already had eye strain. Instead of asking people to remember the rule, they installed reminder software that used the laptop's webcam to check gaze direction every 10 seconds. After 20 minutes of screen work it demanded a 20-second look at a distant target, and the prompt could not be dismissed until the break was actually taken. Symptoms were measured before the two-week reminder period, after it, and again a week after the software was removed.
What improved:
- Dryness, light sensitivity and ocular discomfort scores went down significantly.
- Blink count went up; sustained gaze duration went down.
What did not:
- Binocular vision measures showed no significant change. Two weeks of breaks was not enough to move how the eyes work together.
- Symptoms rebounded once the reminders stopped. The benefit tracked the behaviour, not a lasting change.
So: a small, short study, with an enforcement mechanism most people will not replicate, showing real symptom relief that disappears when you stop. That is a genuinely useful result — and it is a long way from "proven treatment".
Two more honest notes. Anshel himself has said the rule cannot stop or reverse myopia progression. And the American Academy of Ophthalmology's computer eye strain page does not mention 20-20-20 at all, while Mayo Clinic's eyestrain guidance does recommend it. Professional bodies differ, which is another sign this is a practical heuristic rather than a clinical protocol.
Bottom line: 20-20-20 is a free, low-risk reminder with modest evidence that it relieves dry-eye and discomfort symptoms when you actually do it. It is not a treatment, not a myopia-control strategy, and not a substitute for an eye exam or a decent desk setup.
How to do it so it counts
- Set a 20-minute interval. Use a timer rather than your memory. The study that found a benefit had to force compliance; assume you will forget otherwise.
- Find a genuinely distant target. Out of a window, down a corridor, at the far wall of a large room. Six metres is the point — beyond that, accommodation is essentially relaxed.
- Hold it for at least 20 seconds. Let your gaze wander over the distant scene rather than fixing on one spot.
- Blink fully and slowly, several times. Close the lids completely. This is the part that addresses dryness, and it is easy to skip.
- Do not watch a countdown on the screen. A 20-20-20 break spent staring at a timer is not a break. Look away; the timer can beep when it is over.
Things that do not count as the "20 feet" part:
- Your phone at arm's length — that is still near work.
- A second monitor next to the first.
- Closing your eyes. Restful, but it does not change focal distance.
- A wall two metres away. Better than the screen, not equivalent to six.
Making it stick
The failure mode is not ignorance, it is adherence. Everyone knows they should look up; almost nobody does it during a deadline. Two things help:
- Externalise the reminder. A timer that makes a sound you cannot ignore beats an intention. Our 20-20-20 timer runs in a browser tab with a full-screen reminder and a chime; the break timer adds longer intervals and daily counts if you want to see whether you are actually taking them.
- Attach it to something you already do. End of a task, sending an email, finishing a meeting. Habit stacking survives busy days better than a clock does.
Expect the benefit to fade if you stop — that is what the 2023 study found. This is a maintenance habit, not a course of treatment.
What the rule will not fix
If you do 20-20-20 faithfully and your eyes still hurt most days, the rule is not the problem. These are, roughly in order of how often they are the real cause:
- An uncorrected or outdated prescription. Even small amounts of uncorrected astigmatism or the onset of presbyopia make near work disproportionately tiring. No break schedule compensates for it.
- Monitor position. Too close, or too high. The AAO suggests about 25 inches — roughly arm's length — with your gaze angled slightly downward, which also means your lids cover more of the eye and less tear film evaporates.
- Glare and bad lighting. A window behind you reflects in the screen; a window in front of you makes you squint. Overhead lighting that is far brighter than your screen forces constant adaptation. Our color temperature chart covers picking light that matches the time of day.
- Dry eye disease. If the tear film is genuinely deficient, breaks help at the margin but you may need lubricating drops or treatment.
- Text that is too small. Increase it. Squinting is a focusing problem you can solve in one settings change.
20-20-20 versus other break schedules
These solve different problems. Short visual resets and longer physical breaks are not interchangeable, and running both is usually better than picking one.
| Schedule | Targets | Trade-off |
|---|---|---|
| 20-20-20 | Eye focusing fatigue, dryness | Frequent enough to interrupt flow, but each break is trivial |
| 30 / 5 | Neck, back, circulation | Long enough to stand and walk; eyes get fewer resets |
| 50 / 10 | Deep work plus a real reset | Needs a calendar that protects the hour |
| Pomodoro 25 / 5 | Task initiation, procrastination | A productivity system, not a visual-health protocol |
| 15 min every 2 hours | The pre-1991 default | Too infrequent — symptoms arrive long before the break |
When to see an eye care professional
Book an exam if you have eye pain or headaches most days, if symptoms persist after a couple of weeks of consistent breaks and a corrected setup, or if you notice blur, double vision, or trouble refocusing. Sudden vision loss, a shower of new floaters, or flashes of light are urgent — seek same-day care rather than adjusting your timer.
This page is general wellness information, not medical advice, and does not replace an examination by a qualified professional.
Sources
- Chou B. "Deconstructing the 20-20-20 Rule for digital eye strain." Optometry Times, 22 February 2018. Origin of the rule, the 3Bs, and the state of evidence at that time.
- Talens-Estarelles C, Cerviño A, García-Lázaro S, Fogelton A, Sheppard A, Wolffsohn JS. "The effects of breaks on digital eye strain, dry eye and binocular vision: Testing the 20-20-20 rule." Contact Lens and Anterior Eye. 2023;46(2):101744. PMID 35963776.
- American Academy of Ophthalmology. "Computers, Digital Devices, and Eye Strain." Blinking, viewing distance, gaze angle and brightness matching.
- Mayo Clinic. "Eyestrain — Diagnosis and treatment." Recommends the 20-20-20 rule alongside lighting and glare changes.
Stop trying to remember
The timer does the remembering. One button, no account, nothing uploaded.
Frequently asked questions
Does the 20-20-20 rule prevent or reverse short-sightedness?
No. Jeffrey Anshel, the optometrist who coined the rule, has explicitly said it cannot stop or reverse myopia progression. It targets comfort symptoms — dryness, irritation, tired eyes — not the shape of the eye. If you are worried about a changing prescription, that is a conversation with an eye care professional.
Is 20 seconds really enough?
It is the minimum that makes sense. Accommodation — the focusing effort your eye makes for near work — takes roughly that long to release, so a two-second glance at the wall does very little. Longer is fine and probably better; 20 seconds is the floor, not the target.
Do I need blue light glasses to make it work?
No. The American Academy of Ophthalmology states there is no evidence that blue light from digital devices damages the eye, and it does not recommend blue-light-blocking glasses for computer eye strain. The strain comes from how you use the screen — sustained near focus, reduced blinking, glare — not from the colour of the light.
What if my room is too small to look 20 feet away?
Use the farthest point you have: a window, a doorway into another room, the opposite corner. The mechanism is a change of focal distance, so more distance is better, but a genuine shift away from the screen still beats continuing to stare at it. If you can, stand up and walk to a window — that also gives your neck and back a break.
Does it work for phones and tablets?
The principle is the same, and phones are usually held closer than a monitor, so the focusing demand is higher. The practical difficulty is that a phone is portable and the habit is less anchored to a desk. A timer you actually notice matters more than the interval you pick.
How is this different from the Pomodoro Technique?
Pomodoro (25 minutes of work, 5 minutes off) is a productivity system aimed at task initiation and procrastination. 20-20-20 is a visual-health reminder with a break so short you never leave your desk. They are compatible: you can run 20-20-20 inside a Pomodoro block.