LULU GARCIA-NAVARRO, HOST:
Screen time has gone up during the pandemic. Many of us, of course, are working from home. Kids are schooling at home, clicking on computers rather than raising their hands in classrooms. And this has resulted in what's known as digital eye strain, tired and dry eyes from so much screen time. So some have turned to blue light-blocking glasses. Sales have more than doubled during the pandemic, but are they worth the cost? Dr. Mark Rosenfield is a professor at the College of Optometry at State University of New York. He conducted two studies on the effectiveness of blue light-blocking glasses on digital eye strain, and he joins us now. Welcome to the program.
MARK ROSENFIELD: Thank you.
GARCIA-NAVARRO: So what did your study discover about wearing these glasses?
ROSENFIELD: Both of the studies actually found that the blue-blocking filters have no effect, no significant effect on digital eye strain. This didn't really come as a major surprise to us because there really is no mechanism whereby the blue light should be causing digital eye strain.
GARCIA-NAVARRO: I have to say that feels like a big reveal, but I'm not surprised. It always feels like these things might just be sort of gimmicks. I mean, how did you prove that in your study?
ROSENFIELD: Well, we did two studies. The first study, we used the filter that blocked almost 100% of the blue light. And we had the subjects read from a tablet computer for about 30 minutes. And we found no significant difference in symptoms, whether they were using the blue-blocking filter or they were just using a tinted lens, in effect. Now, because that filter blocked almost 100% of the blue light, and very few commercially available lenses actually do that, we redid the study. But this time, we used commercially available spectacle lenses that typically only block around 20 to 25% of the blue.
And the second study was done on a double-blind basis, which meant that the subjects didn't know whether they were looking through the blue-blocking filters or just a clear lens. And the experimenter also didn't know which lens that the subjects were looking through. And again, we found exactly the same effect - that the blue-blocking filters produced no significant change in symptoms of digital eye strain.
GARCIA-NAVARRO: So what is the cause of digital eye strain?
ROSENFIELD: We think - it's not so much the screens themselves but rather the way people use them. They tend to hold them at pretty close distances, especially smartphones. We found that people were holding them sometimes as close as 8, 9 inches away, whereas printed material is typically held around 16 inches away. And also people tend to look at these screens for very long periods of time without taking breaks.
GARCIA-NAVARRO: So these glasses - are they good for anything at all?
ROSENFIELD: The only thing they may be good for is that studies have shown the blue light can interfere with our bodies' light cycle. So we all have natural rhythm so that we know when we get tired, when it's time to go to bed. If you want to look at your screen late at night, which probably isn't a good idea - but unfortunately many of us still do, then the blue-blocking filters might be useful in that regard.
GARCIA-NAVARRO: So what can we do to sort of minimize digital eye strain, since so many of us are needing to be in front of a screen at this time?
ROSENFIELD: Well, taking breaks, I think, is very important. We talk about the 20, 20, 20 rule, where every 20 minutes it's a good idea to look at something at least 20 feet for at least 20 seconds. Try and increase the viewing distance, especially with a handheld device like a phone or a tablet. Don't hold it so close because the closer you hold something, the harder the eyes have to work to focus. So we recommend the device should never be less than 16 inches away.
GARCIA-NAVARRO: Dr. Mark Rosenfield is a vision researcher at State University of New York. Thank you so much.
ROSENFIELD: My pleasure. Thank you.
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