Just one hour increases the risk.
Spending extended time looking at smartphones or other screens may significantly increase the risk of developing nearsightedness, according to a recent study review. Each additional hour of daily screen use is linked to a 21% higher chance of myopia, as reported in JAMA Network Open. The risk continues to rise with increased screen exposure, particularly for those spending four or more hours on devices daily.
Researchers led by Young Kook Kim from Seoul National University College of Medicine observed that the risk of nearsightedness rises sharply with one to four hours of screen time, then increases more gradually after that. They suggest that limiting screen exposure to less than one hour per day could help reduce the risk, noting that exceeding four hours a day significantly raises the odds of developing myopia.
With nearly half of the global population projected to be nearsighted by 2050, environmental factors such as increased screen use and decreased outdoor time are considered major contributors to this trend. According to the American Academy of Ophthalmology, nearsightedness causes distant objects to appear blurry, while close-up tasks like reading remain clear. The rise in screen use, particularly among children, has introduced new types of close-vision activities that contribute to the problem.
The review, which analyzed data from 45 studies involving over 335,000 people, showed a clear connection between screen time and the risk of nearsightedness. This risk persists even when accounting for other close-vision activities like reading or writing. Researchers concluded that reducing overall near-work activities, including screen time, while promoting more outdoor activities, would be a more effective approach to preventing myopia.
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