Prior to 2020, results of studies of digital device use as a risk factor for myopia were inconclusive, but this year may provide a large and unique data set. Since March, children across the country have engaged in distance learning as schools closed in the pandemic. While digital devices have been an integral part of in-school learning for some time, this year they were the exclusive mode of education for myriad students for months. As a result, eyecare professionals are waiting to see the impact of increased screen time on myopia risk.
Myopia occurs when the eyeball is too long (axial length) or its focusing power is too strong (lead of accommodation), causing light to focus in front of the retina. Before the pandemic, myopia was increasing globally at an alarming rate. In the U.S. alone, the incidence of myopia doubled from 20 percent to 40 percent in 30 years, with no sign of abating. Risk factors for myopia include long periods of near work and reduced exposure to sunlight. Increased use of digital devices can increase both of those risks.
Regarding near work, research has shown that children should avoid working at distances closer than 12 inches, resulting in the need for increased focusing power. However, children tend to view screens, phones in particular, even closer than they view books. One ophthalmologist noted that focus is variable when reading a book because we turn pages and can move the book, but when viewing a computer screen, distance and position don’t change. And Yi Pang, MD, OD, PhD, associate dean for research at Illinois College of Optometry noted research has shown that longer time on near work and/or shorter working distance can increase myopia progression. Recommended minimum viewing distances for digital devices are 24 inches for computer screens and 12 inches for phones and tablets.
More time with screens also results in less time outdoors. Sunlight releases an ocular growth inhibitor that works against eyeball elongation which results in myopia. What’s more, focus is at a distance outdoors, and there is speculation that pupils are more constricted, causing a greater depth of field and less image blur, decreasing stimulus factors for myopia. Researchers around the world have found that children who spend at least two hours a day outside, even if it’s intermittent, have a lower incidence and slower progression of myopia.
The unique circumstances of 2020 will likely contribute a great deal to myopia research. Until we know more, however, remind your young patients to keep a proper distance from screens, and as our mothers said, “Go out and play.”
• Linda Conlin
Pro to Pro Managing Editor