The studies included 335,524 participants (mostly children, average age of 9).

The studies were all observational (34 cross-sectional studies, 10 cohort studies/longitudinal studies, and 1 case-control study). Digital screen time was defined as time spent on devices like smartphones, tablets, gaming consoles, computers, and televisions.

In studies that measured total screen time across multiple device types, the researchers found a 28% higher odds of myopia per hour of screen time.

A dose-response analysis found that the odds of myopia increased after 1 hour per day of screen time and increased further with additional screen time beyond that point, with a diminishing rise after 4 hours of screen time per day.

The correlation between screen time and myopia

The solid line is the odds of myopia and the shaded area represents the 95% confidence interval.

Screen time and nearsightedness: Are screens leading us to a future of blurry vision? Original paper