Children’s eyes are still crystal clear and therefore particularly sensitive. The slightly clouded eyeball of adults offers a certain degree of protection against blue light; however, the unnatural screen light hits the retina unfiltered in children and adolescents.
In a world where screens have become an integral part of everyday life and even primary school children have smartphones, it is important to watch the potential impact of this widespread usage closely.
In this blog post, we will look at two of the most important issues when it comes to the health and well-being of children and adolescents in this context: myopia and the role of light and melatonin in sleep.
The increasing incidence of myopia (short-sightedness) in children is an alarming trend that threatens the eye health of the younger generation. Whereas just a few decades ago, short-sightedness in children was considered the exception rather than the rule, today it has almost become the norm.
In Germany, around 15% of children become short-sighted by the end of primary school. This rate rises to an average of 45% by the age of 25, with higher educational achievement being associated with higher myopia rates. There appears to be a direct correlation between the levels of education and myopia. The classic bookworm simply wears glasses.
Today, however, analog books are hardly the culprit – there is solid evidence that the increasing use of digital media plays a major role in children developing myopia. Incidentally, the figures are even more dramatic in Asian countries – a fact that also helps to better localise the mechanisms of development. So what are the reasons for this increasing prevalence of myopia in children?
Nearsightedness or myopia is an abnormality of the eyeball in which near objects are seen clearly but distant objects appear blurred. The term disease or visual impairment is only used for severe short-sightedness from -6 dioptres.
The development of myopia is often associated with two main factors: a lot of screen time and therefore focussing at close range, and limited time outdoors in daylight. Our eyes are extremely adaptable and react to our lifestyle habits as they develop. The current epidemic of short-sightedness is a direct result of our daily demands on the eye.
At birth, a human being is born with an eyeball that is slightly too short and therefore mildly farsighted. In the course of growing up, the eye grows until it is well adjusted to the working distance, i.e. until the image on the retina is in focus. Myopia occurs due to excessive growth in the length of the eyeball, particularly between the ages of eight and 15 – exactly the age at which many adolescents can hardly be kept away from their mobile phones.
The eye optimises itself to the “normal” visual distance and reduces energy-intensive muscle work: the ring-shaped fibres of the ciliary muscle, which change the shape of the elastic lens, have to work less with myopia if you want to look at something up close. However, the focal point of the eye is then in front of the retina, which means that distant objects are only perceived out of focus.
Studies show that playing outdoors can reduce the risk of short-sightedness. In a study in China, significant effects on eye growth were observed even when children only spent an additional 40 minutes outside each day. Initial results indicate that not only the “wide view”, but also bright daylight in particular, contribute to slowing down excessive length growth.
Since the beginning of the century, more and more studies have been conducted to investigate the causes and development of short-sightedness in children. In Asian countries in particular, where the prevalence of short-sightedness among children is especially high, studies are constantly being performed to better understand the correlations and develop preventive measures.
During the COVID-19 pandemic, this topic attracted particular attention worldwide. The knowledge that both screen time and a lack of daylight can accelerate the development of myopia led to the expectation that a negative influence would be detectable, particularly in countries with strict lockdowns.
The study “Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China” is a randomized study.
One group of primary school pupils was “prescribed” a daily 40-minute outdoor school lesson, while a control group continued to experience a normal school day.
The study group had a significantly lower rate of newly diagnosed myopia in the subsequent observation period.
There are a large number of studies on the development of students’ eye health during COVID-19 lockdowns.
A meta-analysis of various studies shows a significant increase in short-sightedness.
However, it should be noted that all of the included studies were from Hong Kong and China, where very strict lockdown restrictions have severely limited the opportunity for outdoor play.
This study from Ireland investigated the relationship between screen time and reading time with myopia in 6-7 year old children.
The group with screen time of more than 2 hours was significantly more likely to have myopia and its precursors.
Incidentally, there was no evidence of a negative influence of reading on eye health, as longer reading times were regularly accompanied by shorter screen times.
When it comes to the prevalence of short-sightedness in children, the focus is primarily on eye health. Another problem related to screen light has an even more far-reaching effect: during the time spent in front of the screen, especially in the evening, melatonin production is suppressed. Melatonin, also known as the “sleep hormone”, plays a crucial role in regulating the sleep-wake cycle. But how do screens and artificial light affect melatonin and therefore children’s sleep?
Artificial light indoors, looking directly at monitors, televisions and smartphones, and “gaming set-ups” with colored LED lighting: the eyes of children and young people are exposed almost continuously to light with an unnaturally high blue component.
A recent study on a small group of preschool children has shown how strongly even dimmed LED light in the evening can suppress melatonin production.
The connection between blue light (in the evening) and a suppression of melatonin production has been widely researched. Depending on the study design, direct measurements of light intensity and melatonin levels are used, or data such as reported screen use and sleep quality are analyzed. The following three studies show a good cross-section of methods and age groups included.
In Japan, a very comprehensive study was carried out on the connection between screen time and sleeping times. “Effects of Screen Viewing Time on Sleep Duration and Bedtime in Children Aged 1 and 3 Years” collected data from over 70,000 children and concluded that higher usage times of portable electronic devices (smartphones, tablets, etc.) are associated with shorter and later sleep.
The above-mentioned study “High sensitivity of melatonin suppression response to evening light in preschool-aged children” investigated how sensitively children react to evening light. 36 pre-school children played at a light table with different light intensities. Even dimmed light could significantly disrupt melatonin production, so that even 50 minutes after playing, levels were still too low.
An analysis of data sets from the “Adolescent Brain Cognitive Development (ABCD) Study” investigated how evening media use affects the sheep quality of 10- to 14-year-olds. All types of media use, such as watching TV/streaming, using social media or exchanging text messages, were associated with poorer sleep, sleep disorders and problems falling asleep.
In a world where screens are ubiquitous, there is growing concern for our children’s health – parents face the challenge of teaching healthy use of digital devices. A complete ban is neither feasible nor sensible in most cases, as media literacy is an important skill for all adolescents. However, it is even more important to protect children’s health and not jeopardize their development. Here are some practical tips on how parents can help their children protect their eyes from the harmful effects of screens:
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