The 20-20-20 rule for screen eyes

The rule

The 20-20-20 rule is a simple habit for anyone who spends long stretches looking at a screen: every 20 minutes, look at something at least 20 feet away, about six metres, for at least 20 seconds. There is no equipment and nothing to learn, and it fits around almost any kind of work.

Twenty feet is roughly the length of a large room or a short corridor. If your space is smaller than that, look out of a window, or as far away as you can. What matters is giving your eyes something distant to rest on.

Both of the big American eye-care organisations recommend it. The American Academy of Ophthalmology calls regular breaks using the 20-20-20 rule the best way to protect your eyes against eye strain, and the American Optometric Association gives the same advice for what it calls computer vision syndrome, also known as digital eye strain.

Why screens tire your eyes

Looking at a screen for hours does not damage your eyes, but it can make them feel terrible. One reason is blinking. The American Academy of Ophthalmology says we normally blink about 15 times a minute, and that studies show this drops to about five to seven times a minute while using computers and other digital screens. Fewer blinks leave the surface of the eye drier and more irritated.

The other is focus. Your eyes work to hold a sharp image of something close, and keeping up that effort for a long time is tiring. Looking into the distance lets the focusing muscles relax. Glare, a screen that is too bright or too dim for the room, and sitting too close all add to the strain. The American Optometric Association lists the most common symptoms of digital eye strain as eyestrain, headaches, blurred vision, dry eyes, and neck and shoulder pain.

Where the rule came from

The rule is usually credited to Jeffrey Anshel, a California optometrist who says he came up with it around 1991, while advising companies about computer eye strain. The standard advice at the time was a 15-minute break every two hours, and he found that people with screen-related eye problems were noticing them well before that. The catchy name, he says, came out of radio and TV interviews.

The longer break has not gone away. The American Optometric Association still suggests resting your eyes for 15 minutes after two hours of continuous computer use, on top of the 20-second breaks.

Does it work?

For years the rule was recommended mainly because it is cheap, harmless and makes sense, with little research on the rule itself. A small study published in Contact Lens and Anterior Eye in 2023 tested it directly: 29 people with eye-strain symptoms had software on their laptops remind them to follow the rule for two weeks. Their eye strain and dry-eye symptoms improved. One week after the reminders stopped, the improvement had gone.

That second finding is the useful one. The rule seems to help while you are actually doing it, and it is easy to forget once you are absorbed in your work. It needs a reminder.

How to make it a habit

A few things make the difference between knowing the rule and following it:

• Pick your spot once. A window is ideal; otherwise the far end of the room or a corridor. Deciding in advance means you do not have to think about it every time.
• Make it the full 20 seconds, not a glance. Let your eyes settle on the distant point and blink a few times.
• Let something else keep time. Watching the clock yourself defeats the point of getting absorbed in your work.
• Every couple of hours, take a proper break: stand up, move around and look out of a window.
• Fix your setup too. The American Academy of Ophthalmology suggests sitting about 25 inches from the screen, roughly arm's length, with your gaze slightly downward, and matching the screen's brightness to the light around you.

What it will not fix

The rule is for comfort, not a cure. It will not correct blurry vision that needs glasses, and Anshel himself says it does not stop short-sightedness from developing or getting worse. If your eyes hurt, your vision changes, or the symptoms stay with you after you have stepped away from the screen, see an optometrist or an ophthalmologist.

For eyes that feel dry, the American Academy of Ophthalmology suggests artificial tears, and if you wear contact lenses, switching to glasses now and then gives your eyes a break.

Using the 20-20-20 Eye Rest timer

The 20-20-20 Eye Rest timer does the remembering. It runs six rounds of 20 minutes of screen time. After each one, a voice tells you to look far away, and the last five seconds of the 20-second break are counted out loud so you know when to go back. Every second break is a two-minute stand-and-stretch instead, and the whole run lasts just over two hours.

Keep it running in its own tab while you work in another; it keeps time in the background. When you want a longer break, Desk Reset is five minutes of gentle stretches to undo a long sit.