Break Reminder

Every 20 minutes of screen work, look at something about 20 feet (6 metres) away for at least 20 seconds. The rule was popularised by optometrists as a simple response to digital eye strain: dry, tired eyes, blurred vision and headaches after long sessions in front of a screen. Looking into the distance relaxes the ciliary muscle that keeps the lens focused at reading distance, and the pause reminds you to blink, since blink rate drops by half or more when people stare at screens.

The reminder here runs the cycle for you: a work interval, a soft chime, a short countdown for the break, then the next interval, with a session counter so you can see how many breaks you have actually taken. It keeps running in a background tab, so leave it open beside your work.

The evidence for 20-20-20 specifically is modest but positive: small trials report reduced eye-strain symptoms when people follow it, and there is no downside. The bigger effects come from the things the break prompts you to do: blink, adjust posture, and drink water. A few additions that have better support:

• Screen position. Top of the screen at or slightly below eye level, an arm's length away. Looking slightly down keeps more of the eye covered by the lid and reduces drying.
• Lighting. Avoid a bright window behind the screen or behind you. Match the screen's brightness to the room.
• Text size. If you lean in to read, increase the font size. Most strain is from squinting, not from the screen itself.
• Movement. Stand up during at least some breaks. Musculoskeletal complaints from sitting are more common than eye complaints, and a 20-second stand costs nothing.

Twenty minutes is a default, not a law. Programmers and writers in deep work often prefer 45 or 50 minutes with a longer two- or three-minute break, which is closer to the Pomodoro rhythm; if that is you, the timer in Pomodoro Mode or the focus timer may fit better. People with existing eye strain, contact-lens wearers and anyone in dry, air-conditioned offices benefit from shorter cycles, such as 15 minutes. Set the work length, break length and sound to suit, and the tool remembers the choice on this device.

Our guide to the 20-20-20 rule explains the physiology of eye strain in more depth and what to do if symptoms do not improve.