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Be careful what you believe about screen time making you blind

Be careful what you believe about screen time making you blind


The science behind the latest screen-time scaremongering

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If you believe the headlines that have been circulating over the past few weeks, staring at screens is ruining our eyes. “Blue light from phones, tablets could accelerate blindness and hurt vision, study finds,” USA Today declared. Only, that particular study didn’t actually test the blue light that comes out of screens — and it didn’t look at the light’s effects on actual eyeballs.

We’ve been through this before: there is some evidence that blue light can disrupt your sleep schedule. And some research suggests blue light might damage rat retinas. But that doesn’t mean that the blue light from screens does the same thing to people — and ophthalmologist Rebecca Taylor told The Verge earlier this year that “the devices that we use do not appear to cause long-term eye damage.”

It didn’t look at the light’s effects on actual eyeballs

Still, there’s a new round of blue-light hysteria going on, and you can trace it back to a paper published last month in the journal Scientific Reports. It showed that a molecule that’s key for sensing light in the eye, called retinal, combined with blue light, can damage and kill cells. No wonder people are freaked out.

So I asked the paper’s senior author, chemist Ajith Karunarathne at the University of Toledo in Ohio, whether his results mean that staring at my tablet or iPhone will make me go blind. His answer was simple: “Absolutely not.”

What does this latest blue light study actually show? It’s more about how blue light could cause damage, rather than whether it actually does so in the eye itself. The whole thing started because Karunarathne’s lab studies how to make cells move in response to light the same way they move in response to the chemicals squirting around the body. “Have you seen those videos that show cats following a laser pointer on the ground?” Karunarathne asked. It’s kind of like that — just, smaller.

Light’s easier to control than chemicals — and the idea is that if you can turn cell movement on and off with the flip of a switch, it might help scientists tease out how different cells contribute to complex biological processes. It’s like silencing the violins in an orchestra to see how important they are to the overall melody. To make cells responsive to light, the team basically added eye features to non-eye cells. They took the proteins that detect light in the eye, called photoreceptors, and tricked other types of cells — like, say, cancer cells — into producing them. Then, they added a key ingredient called retinal, a molecule that photoreceptors need in order to sense light.

That’s when they discovered that blue light damaged or even killed these cells — and they set out to figure out why. The photoreceptors themselves didn’t seem to be to blame. So could it have been the retinal, combined with the blue light? The answer, according to their new Scientific Reports paper, is yes.

But there are a bunch of key caveats here that are missing from some of the more breathless coverage. First off, those cells were in a dish, not an eyeball.  And the cells included cancer cells, immune cells, and yes, a type of cell found in the eye. But while they showed one way that blue light can damage cells, Karunarathne says, “The question is whether it’s happening in the eye.”

And that, they don’t know yet. It’ll take more research to figure out. “We haven’t done any experiments with the light coming out of digital devices, or any other digital screens,” Karunarathne says. “So, I have to limit our conclusions.” It’s a good idea for us to do the same.