Nowadays, our eyes are often fixed on glowing computer, phone and television screens for huge portions of the day — whether for work, school or leisure. But after hours of screen time, you may notice pain around your eyes, and over longer periods of time your vision may worsen.
But how does excessive screen time actually damage the eyes?
"We are born long-sighted," meaning babies tend to see far-off objects more clearly than close-up ones, Neema Ghorbani Mojarrad, an assistant professor at the University of Bradford in the U.K. and a registered optometrist, told Live Science. "As we grow, our eyes respond to the visual environment and genetic signals to get to perfect vision," he said.
In people with myopia, or nearsightedness, the eye fails to stop this adjustment process, and "the eye continues to grow in length," increasing the distance between the front of the eye and the internal lens and light-sensitive retina at the back of the eye, Ghorbani Mojarrad said. Frequently engaging in close-up work, including that which uses screens, is a factor that can drive this harmful change, he explained.
Related: How do our eyes move in perfect synchrony?
When we focus on something in close proximity, the eye's ciliary muscles — which adjust the shape of the lens — contract, giving the lens a more spherical shape to focus the image onto the retina. It is hypothesized that overuse of the ciliary muscles can lead them to thicken, weakening the eye's ability to relax the lens back into a flattened shape.
This can elongate the eyeball, causing permanent changes to its structure and ability to focus light on the retina. When looking at far-away objects with elongated eyes, a person's point of focus ends up "in front" of the retina, making the objects appear blurry.
When we use screens, they are usually in close proximity to our face, which is why excessive screen use can contribute to the development of myopia.
Screen use can pose an even greater risk to children, whose eyes have yet to fully develop. A 2021 meta-analysis of more than 3,000 studies published in the journal Lancet Digital Health found a significant relationship between screen time and myopia in young people. Another study, published in the journal BMJ Open in 2022, found that increased use of digital devices for remote learning during the COVID-19 pandemic induced or exacerbated visual disturbances in children, including rapid progression of myopia.
Factors such as a lack of outdoor time, engaging frequently in prolonged close-up work and a person's genetics can also raise their risk of myopia, Ghorbani Mojarrad said. As rates of myopia have swiftly risen in recent years, particularly in children, Ghorbani Mojarrad explained that lifestyle factors, including excessive screen time, rather than genetics, are most likely to blame for the uptick.
And the problem could worsen. By 2050, half of the world's population could have myopia, and the condition may become a leading cause of permanent blindness globally, a 2016 study predicted based on a review of studies on the changing prevalence of myopia.
Myopia can cause permanent blindness because it is a risk factor for other eye conditions. A 2019 study in the journal Community Eye Health found that the risk of developing myopic macular degeneration — a condition that can lead to significant, permanent sight loss — rises as the severity of myopia increases. Retinal detachment is also five to six times more likely in those with high- versus low-myopia, meaning severe versus mild nearsightedness.
The World Health Organization recommends no more than one hour daily screen time for children under age 5, and none for those under 1 year old. Children are now being diagnosed at younger ages than in the past, Ghorbani Mojarrad noted, and the earlier myopia develops, the worse the outcome can be. If you become myopic at a younger age, by the time your visual development stabilizes, you are much more likely to be more myopic than if the onset of myopia was later, he said.
Ghorbani Mojarrad advised limiting screen time and close-up work and increasing time outdoors to delay the onset and progression of myopia.
This article is for informational purposes only and is not meant to offer medical advice.
Editor's note: This story was updated on Sept. 8, 2023 to clarify some of Ghorbani Mojarrad's quotes. The article was first published on Aug. 16.
