Screen breaks, and the 20-20-20 rule

Every twenty minutes, look at something twenty feet away, for twenty seconds. Simple enough to remember and almost impossible to remember — here is why, and what to do about it.

What the rule is

Every 20 minutes of screen work, look at something about 20 feet away (six metres — in practice, the far wall or out of a window) for at least 20 seconds. That is the whole thing. It is standard optometry advice for digital eye strain, and its value is that it is short enough that you have no excuse.

Why a monitor tires your eyes

Two reasons, and neither is blue light, which gets far more attention than it deserves.

The first is sustained near focus. The muscle that focuses your eye holds a contraction for as long as you look at something close, and holding any muscle contracted for four hours is tiring. Looking into the distance is what releases it — which is why the distance in the rule matters more than the twenty seconds.

The second is blinking. Blink rate drops substantially when you're concentrating on a screen, which leaves the surface of the eye drier than it should be. That is most of the grittiness people describe at the end of a long day.

The reason it never happens

Not laziness. The problem is that twenty minutes of focused work feels like four minutes, and there is no internal signal that any time has passed at all. You cannot notice a thing you are not equipped to notice, so relying on your own sense of the clock is the part that fails.

That leaves two options: attach the break to an event that reliably recurs, or put the cue outside yourself. Events work well if your day has them — end of a call, end of a file, every time you send something. If your day is one unbroken block of work, an external reminder is the only thing that survives contact with a deadline.

What counts as a break

Looking at your phone is not a screen break. It is a smaller screen held closer to your face, which makes both of the problems above worse rather than better.

A good ninety seconds looks like: stand up, look at the furthest thing in the room, roll your shoulders once, drink something, sit back down. Every part of that is doing a different job, and together they cost less time than reading one email.

• Standing resets the hip and back position — see the desk stretches if something already aches.
• Looking far away releases the focusing muscle.
• Drinking handles the thing you have been forgetting since 10am — water reminders.
• Two slow breaths cover the twenty seconds without you having to count — breathing exercises.

Making the cue external

unwind is one page you can leave open and come back to, with no login and nothing to configure. If the browser is where you live all day, the extension puts the nudge in the same window as the work — which is the difference between a reminder you act on and a notification you swipe away.

If your eyes hurt persistently, or your vision changes, that is an optician's job rather than a rule's. This page is general information, not medical advice.

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