The 20-20-20 rule, and a free timer for it

What the 20-20-20 rule is

The rule fits in one sentence: every 20 minutes, look at something about 20 feet (6 m) away for at least 20 seconds. It is a prompt to change where your eyes are focused during long stretches of close-up work on a screen, such as reading, writing, coding, spreadsheets or video calls.

Two professional bodies list it as a habit for people who use digital devices. The American Academy of Ophthalmology puts 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 describes the same habit in its guidance on computer use and adds a longer rest of 15 minutes after two hours of continuous computer work.

That is all the rule asks. It doesn't require exercises, special glasses or leaving your desk, which is a large part of why it is easy to remember and easy to try.

Where it comes from

The rule is commonly credited to Jeffrey Anshel, an optometrist who wrote about visual ergonomics in the workplace in the 1990s. In an interview with Optometry Times, he describes reading a study that found shorter, more frequent breaks from computer work worked better than one long break every couple of hours, and turning that idea into a phrase people could remember.

The three twenties were picked to be easy to remember. Twenty minutes is often enough to break up a long session, and twenty seconds is short enough that it barely interrupts your work.

Why 20 feet (6 m)?

Eye care professionals treat about 20 feet, or 6 metres, as the point where the eyes focus at "distance". Light from things that far away reaches the eye almost parallel, so the eye no longer has to adjust its focus the way it does for a screen at arm's length. It is the same distance used for standard eye charts, which is where the "20" in "20/20 vision" comes from.

You don't need to measure it. A window, the far end of a corridor or the other side of a large room all work. In a small room, look at the farthest thing you can see.

What the evidence does and doesn't show

The 20-20-20 rule is widely repeated, but few studies have tested it directly, and the ones that have are small. In one of the most cited, a study in Contact Lens & Anterior Eye (published online in 2022), 29 computer users who already had symptoms used software that reminded them to take 20-20-20 breaks for two weeks. They took more, shorter breaks and reported fewer symptoms while the reminders ran. One week after the reminders stopped, that difference was gone. Measurements of their tear film and the surface of the eye did not change, and nearly all of the binocular vision measurements stayed the same.

So the honest summary is this: the rule is a habit that eye care organisations recommend, not a treatment. A single study of this size can't tell you what the rule will do for you. The 20-foot and 20-second figures are a convenient convention rather than tested thresholds.

This page is general information, not medical advice.

Making the habit stick

• Use a reminder. Time on a screen is easy to lose track of. A timer such as the one above, or an app, does the remembering.
• Pick your spot in advance. Decide on one far-away thing you can see from your desk, so the look-away takes no thought.
• Blink. The AOA suggests blinking often while you use a computer, and the AAO notes that people blink less while using computers.
• Set up the screen. The AAO suggests sitting about 25 inches (about 63 cm), roughly an arm's length, from the screen and matching its brightness to the room. The AOA suggests a screen 20 to 28 inches (50 to 70 cm) from the eyes, with its centre 15 to 20 degrees below eye level.
• Don't fight your calendar. A reminder in the middle of a call or a presentation tends to get dismissed. Taking the look-away at the next natural pause is easier to stick with.
• Add longer breaks too. The AOA's guidance also includes a 15-minute rest after two hours of continuous computer use.

When to see an eye doctor

A timer can't tell you why your eyes feel the way they do. If discomfort, blurred vision or headaches keep coming back, or your vision changes, see an optometrist or ophthalmologist. They can check your eyes and whether your glasses or contact lenses suit the distance you work at. The AAO also says an ophthalmologist can help if eye strain continues after you have adjusted your workspace.

Get help promptly for sudden changes in vision, eye pain, or anything else that worries you.

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