All about screen time and close work

• Use of digital screen time is linked to development of myopia in children and teenagers, also called short-sightedness or near-sightedness.
• Excessive digital screen time is also linked to dry eye syndrome, digital eyestrain, and poor head and neck postures which can cause pain.
• Screens appear to be a bit harder for our visual system to read from than books, with slower reading rates and more eyestrain symptoms.
• Screen time recommendations are zero hours (except for video calls) for kids under 2; 1 hour per day co-watched with parents for 2 to 4-year-olds; and 2 hours per day of leisure screen time in 5 to 17-year-olds.
• Three easy screen time rules are described: the elbow rule, the 20/20 rule and the two-hour rule.

Myopia is an eye condition which causes blurred far vision, and is also known as short-sightedness or near-sightedness. Once myopia develops in children and teenagers, it typically deteriorates every few to several months. In most cases, this worsening continues until the late teens or even early 20s.¹ This is called progressive myopia, which is a significant concern to quality of life in children and teenagers, and also poses risks to long-term eye health.²

There have always been ‘bookworm’ children who spent a lot of time looking up close and reading, and there has always been myopia. What's different today is the dramatic increase in myopia across the world, which indicates that there’s an additional influence of the environment on the visual development of today’s children. This appears to be a combination of not enough time spent outdoors, and too much time spent on screens and/or looking up close.³ 

Use of digital devices is increasingly important for schooling, and screen time can be beneficial when balanced well with other activities. Spending too much time on screens is a concern for parents as excessive use can impact development of good vision as well as physical and mental health outcomes.

Children exposed to screens before age 3 are more likely to have developed myopia by pre-school age.⁴ There is an increasing volume of research indicating the link between screen time and myopia development in children and teenagers,^5,6 although the negative impacts seems to be greatest in children under 10, at this crucial stage of visual development.⁶

Screen time in children and teenagers has also been linked to development of dry eyes and digital eyestrain, which can cause significant symptoms of uncomfortable eyes, blurred vision, headache and red eyes.^7,8

Children and adults appear to hold screens closer than books and print material. This increases the visual demand on the eyes' focussing system.^9,10 Digital eye strain may be suffered by up to 50% of people who use screens, with symptoms including sore, tired, dry eyes and headaches.¹⁰

Backlit e-readers also appear to cause more visual fatigue symptoms compared to paper books.¹¹ It has also been shown that reading speed is slower on an iPad than printed text.¹²

Eye muscle coordination and teaming is controlled by sets of muscles which work both outside of the eyes to aim them at the correct spot in space, and inside the eyes to focus. Reading for just 30 minutes from a smartphone has been shown to fatigue these muscle systems and make them less flexible to changing focus.¹³

Posture makes a difference for visual and bodily comfort when using screens. In school children aged 11 to 17 years, around one-third preferred using digital devices for reading instead of conventional books, and one-quarter preferred to read while laying down in bed rather than sitting up. These kids were more likely to suffer eye strain.¹⁵

When children aged 6 to 12 years use a smartphone in a laying down posture, it is likely to cause more head and neck, trunk and upper arm discomfort than when sitting up.¹⁶ Children aged 6 to 9 years who used smartphones for longer than 60 minutes were most likely to develop musculoskeletal pain, and laying on their stomach (prone position) while using the smartphone was the most risky posture for pain.¹⁷

A recent study which looked at the posture of children aged 5 to 12 years separated them into two groups, based on whether they used smartphones for an average of more or less than 4 hours per day. The heavy smartphone users showed a more dropped head and neck position, both when sitting and standing. This posture can cause neck stiffness, pain and balance issues,¹⁸ and can even influence breathing function.¹⁹

When it comes to healthy childhood development in general, the following recommendations have been put forward by the World Health Organization, the Australian Government Department of Health and the American Academy of Pediatrics.

• Children under two years of age should have no screen time. Watching a screen at a young age can limit time for active play and learning, reduce opportunities for language development, negatively influence their attention skills and affect the development of the full range of eye movement. The exception to this is video-chatting with family, which can encourage language and social development.
• Children aged 2-4 years should have a maximum of 1 hour of screen time per day, ideally co-watching with a parent. Co-watching, like reading a book together, can make screen time useful for language development and learning. In this age group, excessive screen time has been associated with less active, outdoor and creative play; slower development of language skills; poor social skills and an increased risk of being overweight.
• Children of school age (5-17 years) should be limited to 2 hours of sedentary, recreational screen time per day. Break up long periods of sitting as often as possible, and when using screen-based electronic media, positive social interactions and experiences are encouraged. Reducing screen time before bed and removing screens from the bedroom where possible can be important for healthy sleep habits.

There are three key rules for the childhood visual environment – indoors, which are important for both reducing the risk of a child developing myopia as well as reducing the risk of fast progression, or worsening, once a child has myopia.

1. The elbow rule: keep an elbow-to-hand distance away from books and screens to avoid them being too close to the eyes.
2. The 20/20 rule: take regular breaks from reading to reduce demand on the visual system.
3. The two-hour rule: try to limit leisure screen time (outside of school work) to two hours per day in school-aged children.

THE ELBOW RULE is where your child should try to keep an elbow-to-wrist distance between anything they are viewing up close, and their eyes. Try it yourself, and show them at home – make a fist, put it next to your eyes, and where your elbow sits is the closest any screen or book should get to your eyes when reading. 

THE 20/20 RULE is where you child aims to take a break from reading every 20 minutes, for 20 seconds. He or she should look across the room for that 20 seconds, to relax the focussing muscles in the eyes before recommencing reading or screen time. This can be managed as a break between book chapters, between Netflix episodes for tweens and teens, or timers set for younger children.

THE TWO HOUR RULE is based on guidelines from national and international expert organizations on child health, as described above.

1. Hou W, Norton TT, Hyman L, Gwiazda J; COMET Group. Axial Elongation in Myopic Children and its Association With Myopia Progression in the Correction of Myopia Evaluation Trial. Eye Contact Lens. 2018 Jul;44(4):248-259.
2. Tideman JW, Snabel MC, Tedja MS, van Rijn GA, Wong KT, Kuijpers RW, Vingerling JR, Hofman A, Buitendijk GH, Keunen JE, Boon CJ, Geerards AJ, Luyten GP, Verhoeven VJ, Klaver CC. Association of Axial Length With Risk of Uncorrectable Visual Impairment for Europeans With Myopia. JAMA Ophthalmol. 2016 Dec 1;134(12):1355-1363.
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