The 20-20-20 rule, with a timer

What the 20-20-20 rule is

It is a habit for people who look at a screen for hours: every 20 minutes, look at something at least 20 feet (6 metres) away, for at least 20 seconds. The American Optometric Association recommends it against digital eye strain, also called computer vision syndrome.

Why eyes get tired at a screen

To see something close, the muscle that focuses the eye has to stay tense. Hold it there for hours and it tires, like any muscle. People also blink less while they read from a screen, so the surface of the eye dries out.

The result is tired, dry or burning eyes, blurred vision and headaches by the end of the day. Looking far away relaxes the focusing muscle, and a pause brings the blinking back.

How to follow it

• Set a timer. Nobody notices 20 minutes passing while they work.
• Look out of a window or down a corridor. 20 feet is about the length of a large room, and anything farther works too.
• Blink slowly a few times while you look away.
• Every hour or two, take a longer break and get up from the desk.

What it does not do

The rule is about comfort while you work. It does not treat an eye condition or correct your vision. If your eyes hurt or your vision changes, see an eye doctor.

A timer in this tab, or a break reminder in every tab

The timer above runs while this page stays open, and shows the break in this tab only.

Time to Break is a free Chrome extension that does the same job in the background: every 20 minutes it pauses all of your open tabs for a 20 second break. No account, no data collected.