Screen time and smartphone usage have been proven in many studies to be correlated with myopia in certain populations. The good news is that limiting the amount of continuous time one spends staring at a digital device, as well as increasing time spent outdoors, may ameliorate the effect. Findings from this recent study suggest that smartphone users should take frequent breaks, at least every 20 minutes, to avoid potential vision damage. More time outside may be an even bigger bonus.

The 272 Dutch students included in this population-based study were between ages 12 and16 (54% female). Researchers used a smartphone application that measured the kids’ smartphone use and face-to-screen distance, and posed questions twice weekly about each participant’s outdoor exposure. App and ophthalmic measurements were recorded for 13 months, and smartphone usage was tracked for five weeks. 

The subjects spent an impressive average of 3.71 hours per day on their smartphones on school days and 3.82 on non-school days. The average time the students spent outdoors was 2.37 hours per day on school days and 2.77 on non-school days. The average number of episodes of 20 minutes of continuous use per day was 6.42 on school days and 7.1 on non-school days. Screen time was strongly correlated with continuous use, and outdoor exposure was inversely correlated with the two. In other words, the less time students spent outdoors, the more time they spent on their phones, and usually for more than 20 minutes at a time. 

Continuous use during schooldays (>20 minutes without a pause) was associated with spherical equivalent of refraction (SER) and axial length corneal radius ratio (AL/CR). For each additional 20-minute episode of continuous use, SER was -0.07 D more myopic and AL/CR 0.005 larger. Smartphone use also showed somewhat of an association with SER, though not as significant. However, the same was not true for non-school days or students with high outdoor exposure, suggesting that increased time outdoors may actually curb the negative impact of continuous smartphone usage on myopia refractive error. 

“A higher number of episodes of >20 minutes continuous use was associated with more myopic SER and a larger AL/CR. This association was not present in teenagers with high outdoor exposure, suggesting that outdoor exposure moderates the association,” said the researchers in their study. “Since smartphone use is becoming increasingly popular, awareness of the potential negative consequences of prolonged smartphone use is warranted.”

Further research is needed to determine whether these findings can be generalized for other age populations and how exactly outdoor exposure is able to moderate the visual consequences of smartphones. However, it’s certainly safe to say you should encourage all patients to limit their children’s phone usage, especially episodes of more than 20 minutes of continuous use, and recommend they spend a little more time in the sun (or the shade). Their eyes will thank them.

Enthoven CA, Polling JR, Verzijden T, et al. Smartphone use associated with refractive error in teenagers; the myopia app study. Ophthalmology. 2021. [Epub ahead of print].