How are screens different from books in myopia?

In myopia research, books have traditionally been the primary proxy for quantifying the amount of near work a child might engage in.¹ However, the widespread use of smart devices among children has introduced a new element to how we define and measure near-work activities. While books and screens differ in numerous ways, both have been recognized as factors that can contribute to the development and progression of myopia.^1-3 In this article, we’ll look at the differences between screens and books and the impact they both have on myopia.

There are clear differences between when a child begins viewing media on a screen and when they might start reading a book, largely due to developmental capabilities. Screens offer dynamic visual and auditory experiences that are easier for infants and young children to engage with compared to static images and text in books. Even before the COVID19 pandemic, studies found that most children started using screens from before the age of 3.⁴ This appears prevalent in a wide range of regions, with pre-schoolers in South Korea, Italy, Shanghai and America engaging in screentime from an early age.⁵ Notably, in America 96.6% of infants from low-income backgrounds start using mobile devices before reaching their first birthday.⁶ During the COVID19 lockdowns, children under 4 years old were more exposed to screens than prior to the pandemic.⁷ Early screen exposure from years 0 – 1 year had a statistically significant association with myopia.⁵

On the other hand, near work studies involving books often include children from the age of 6¹ which coincides with the age most children begin formal education and learn to read. Children can be exposed to books earlier, however: a study in Singapore found that the average age a child started to engage with books was around 1.38 years old either independently or with a parent, and that children went to preschool at around 1.5 years old. This early exposure did not show a significant association with myopia though, possibly due to the shorter amount of time spent reading.⁸ There is a limited number of studies investigating the effects of reading on infants, as this age group are typically too young to meaningfully engage with books.⁹ 

Near work for continuous periods of time appears to be the meaningful factor when it comes to increased risk of myopia development and progression, with reading for 45 minutes or longer being a threshold.¹⁰ A study in Ireland indicated that children who use screens for over three hours daily are nearly four times as likely to develop myopia compared to those with less than an hour of screen time each day. This effect is most pronounced in younger children, with 6 to 7-year-olds who are heavy screen users being five times more likely to be myopic than their peers with minimal screen exposure. The disparity in screen time's impact is less evident among 12 to 13-year-olds.¹¹ Studies of children report an average of 3 hours or more a day on screens;^2,12 the average day for an 8- to 18-year-old can include approximately 8 hours of uninterrupted screen use.^13,14 

During the COVID19 lockdowns in Australia, surveys of parents found that many felt their children's screen time was replacing book reading, as evidenced also by the decrease in book purchases and library use.¹⁵ In another study in Ireland, they also found that more screen time was linked to less time spent on reading and writing activities among children aged 6 to 7.¹⁶ 

Short viewing distances of closer than 25cm have been highly associated with myopia.^1,17 Children tend to hold smart devices closer than they would for books, ^13,18   typically at an average distance of 24 cm, closer than the typical 40-50 cm distance for adults.¹⁹ Viewing distance in children appears to be independent of myopia status or arm length, with children holding devices at similar distances regardless of these factors: the median viewing distances ranged between 18.46 cm and 45.68 cm.²⁰ Closer viewing distance is likely due to screen and font size being smaller on a screen than in books.^13,18 This closer viewing distance may contribute to hyperopic defocus and accommodative lag, potentially impacting myopic progression in children.¹⁹

Digital screens are often brightly lit, causing glare sensitivity for some users, which can lead to squinting to reduce light exposure. This action exerts the orbicularis oculi muscle, and can result in eye discomfort, headaches, and fatigue.²¹ Reading speed is slower when reading from an iPad compared to conventional books.²² This could be due to glare sensitivity which can contribute to discomfort and digital eyestrain.^23-25 

There is some implication that myopia development and progression may be associated with poor sleep quality in children.²⁶ Digital devices emit short wavelength light which is thought to impact melatonin levels; hence, blue light blocking filters are becoming increasingly popular for their purported ability to decrease asthenopia and reduce the impact of short wavelength light on the circadian rhythm, thereby improving sleep quality²⁷ (blue light blocking filters have weak evidence for their marketed claims however).^27,28 In contrast, reading books does not involve blue light exposure, suggesting that books may be a better option for sleep quality and, by extension, myopia. However, more research is required before any definitive conclusions can be drawn regarding sleep advice and myopia. 

The differences between screens and books have important implications for eye health and myopia progression in children. Screens offer dynamic and engaging experiences but contribute to increased exposure to artificial light, closer viewing distances, and more time spent in near work, all of which can impact myopia development. Books or digital device access alone do not explain the dramatic increase in myopia prevalence; therefore, understanding and managing digital device use is crucial. Our article Digital eye strain in kids provides tips on managing digital device use in children with guidelines from the World Health Organization, the Australian Government Department of Health, and the American Academy of Paediatrics on digital device based leisure time for children.