The 20-20-20 rule says that every 20 minutes you should look at something 20 feet away for 20 seconds. It has been tested only a handful of times. One small study found it eased eye strain symptoms while people followed it, another found 20-second breaks made no difference, and neither found that it prevents eye strain.
Looking away from your screen is free and does no harm, and there are sound reasons it could help. The specific numbers are a convention, though, and nobody has shown that 20, 20 and 20 are the right ones.
What is the 20-20-20 rule?
The American Academy of Ophthalmology words it as “Every 20 minutes, shift your eyes to look at an object at least 20 feet away, for at least 20 seconds.” The American Optometric Association gives the same advice and adds 15 minutes of rest for your eyes after two hours of continuous computer use.
The rule is usually credited to the optometrist Jeffrey Anshel. He told Optometry Times in 2018 that he came up with the idea around 1991, borrowing from research on rest breaks for musculoskeletal disorders. There’s a rival claim. The word historian Barry Popik found a 1998 Newsday article in which Dean Evan Hart, an associate research scientist at Columbia University, calls it “my ‘20-20-20 rule’”.
Neither account explains where the three numbers came from. Moorfields Eye Hospital’s private clinic suggests looking away every half an hour instead.
Does the 20-20-20 rule work? What the studies found
In that 2018 Optometry Times piece, the author noted that no peer-reviewed study had yet tested the rule. At least four have since.
| Study | Who | What they did | What happened |
|---|---|---|---|
| Talens-Estarelles et al., 2022/23 | 29 computer users with eye strain | Two weeks of reminder software, no control group | Symptoms went down, then returned within a week of stopping |
| Johnson & Rosenfield, 2023 | 30 young adults | 40-minute reading task with 20-second breaks every 5, 10, 20 or 40 minutes | Break timing made no difference to symptoms |
| Alghamdi & Alrasheed, 2020 | 40 eye clinic patients | A booklet about the rule, compared with advice to drink more water, over 20 days | Dry eye symptoms improved, overall symptoms didn’t change significantly |
| Vishal et al., 2026 | 100 healthy adults | 40 minutes of laptop gaming, following the rule or not | Eye focusing and alignment measures deteriorated more without the rule |
The reminder study. Researchers from the universities of Valencia, Bratislava and Aston put software on the laptops of 29 people who had eye strain. It used the webcam to track breaks and blinking, and sent reminders based on the 20-20-20 rule. After two weeks, dry eye and eye strain symptoms had gone down, but one week after the reminders stopped the improvement was gone. Nothing changed in the tear film or on the surface of the eye.
Even with the reminders, the authors write that the rule “did not prevent” digital eye strain. Participants said they spent 7 hours a day at a computer, while the software logged 4. There was no comparison group, and the authors say a placebo effect can’t be completely ruled out.
The study that found no effect. At the SUNY College of Optometry, 30 young adults did a demanding 40-minute reading task on a tablet on four separate occasions, with 20-second breaks every 5, 10 or 20 minutes, or none at all. Symptoms rose every time. The break schedule had no significant effect on symptoms, reading speed or accuracy, and the authors concluded their results “do not support” 20-second breaks as a treatment for digital eye strain. Each session lasted 40 minutes, so the study says nothing about weeks of use.
Two smaller studies. At a Saudi eye clinic, 20 patients got a booklet explaining the rule and 20 were told to drink more water. After 20 days, dry eye symptoms and tear stability had improved, but the overall eye strain score had not changed significantly. A study published on 26 October 2026 had 100 adults play laptop games for 40 minutes. Measures of eye focusing and alignment showed “greater deterioration” in the people who didn’t follow the rule. The abstract doesn’t say whether people were randomly assigned to the groups.
The 2023 TFOS Lifestyle report, a review by an international panel of eye researchers, says treatments for digital eye strain “are not well established” and that encouraging regular breaks “may help”.
Why looking away could help
To see a screen at arm’s length, the lens inside your eye has to hold a near focus. Something 6 metres (20 feet) away needs almost no focusing effort. A 2018 review in BMJ Open Ophthalmology says frequent short breaks can relax the eye’s focusing and eye-turning responses and ease symptoms without hurting productivity.
Blinking also drops. The same review cites a 1991 study where blink rate fell from 18.4 blinks a minute before computer use to 3.6 a minute during it, and its authors suggest this may be relevant to the dry eye symptoms that often come with eye strain. Screens aren’t the only cause, though. In a study of 50 people, blink rate dropped when reading on paper as well, while only reading on a screen increased the share of incomplete blinks. The authors put the drop down to the concentration that reading demands. In the reminder study, the blink rate during screen use stayed low across the two weeks of reminders.
Is 20 seconds long enough?
For shifting focus, yes. The adult eye starts refocusing within roughly 300 to 400 milliseconds.
A small leftover near-focus can take longer to clear. In 386 Beijing schoolchildren, the after-effect of a five-minute reading task took a median of 20 to 50 seconds to fade, depending on their eyesight, and longest in the short-sighted children. Those were children, and adults may differ, but there’s no reason to stop at exactly 20 seconds.
The 20 feet isn’t precise either. The far side of a room or the view out of a window does the same job. Moorfields also suggests closing your eyes for 10 seconds afterwards.
Do you need a reminder?
Maybe not. Before the reminders were switched on, the people in the reminder study already took about 26 natural breaks a day, and their average stretch of continuous computer use was 11 minutes. The reminders prompted about three rule breaks a day. The authors suggest that small change may be why most of their eye measurements didn’t move, and that shorter intervals, or breaks fitted to each person’s habits, might do more.
So check how you actually work. If you regularly go an hour without looking up, a reminder gives you breaks you aren’t taking now. If you already glance out of the window every few minutes, a 20-minute timer adds very little.
A break that gets you out of the chair covers your eyes, neck and back at once. Our guide to movement breaks has ideas, and the 20-8-2 rule applies the same thinking to sitting and standing. SitApp’s free break timer can be set to every 20 minutes. If you get up on your own for at least the length of a break, it counts that as one and restarts the clock.
Other things that help eye strain
Screen position. The AOA suggests putting the screen 20 to 28 inches from your eyes and 15 to 20 degrees below eye level. Our guide to monitor height covers how to set that up without craning your neck.
Blue light glasses. The TFOS report found that, on the best current evidence, blue-light blocking interventions “do not appear to be an effective management strategy” for digital eye strain.
If you get headaches along with sore eyes, our guide to posture headaches covers the ones that come from the neck.
Does screen time damage your eyes?
No. The AAO says eye strain “does not injure the eye and does not cause permanent damage”. If you’re still getting it after changing your setup, the AAO’s advice is to see an eye doctor, who can look for dry eye, problems with the eye muscles, or a prescription that needs updating.
FAQ
Does the 20-20-20 rule prevent eye strain? No study has found that it does. The best evidence is that it may ease symptoms while you keep it up.
Who invented the 20-20-20 rule? It’s usually credited to optometrist Jeffrey Anshel. A 1998 newspaper article quotes Columbia University researcher Dean Evan Hart calling it his own.
Does it have to be exactly 20 feet? No. Anything far enough away that your eyes stop focusing up close will do.
