Screens, near work and breaks

The short version

Near work is work for a child's eyes, and a tablet is a book you hold closer. What matters is three dials, not one clock: how close, how long without a break, and how much light. Hours alone do not predict myopia well; hours multiplied by closeness do. A phone at twenty centimetres is a bigger dose than a television across the room. Breaks every half hour or so, a working distance the length of a forearm, and bright light at the desk do more than a timer app. The 20-20-20 rule is harmless but it was invented for adult eye strain, not for stopping an eye growing — this topic separates the two.