And unless you're watching this far in the future after we've had some sort of apocalypse, there are screens all around us.

So of course, a lot of people are worried that exposure to all this unnatural light is harmful.

But can digital screens really hurt you?

Well, at the very least, they can can cause temporary annoyances like headaches.

But the research is still out on permanent damage.

If you stared at a screen for too long, you may find yourself feeling what's known as digital eye strain, or computer vision syndrome.

The most common symptoms are blurred vision, headache, and pain in the neck and shoulders.

Unfortunately, even though we know it's connected to spending a bunch of time looking at a screen, there are a bunch of potential causes —

from screen viewing making you blink less often and squint more, to it affecting your pupil response time, to it exposing you to more blue light.

Or people could be suffering from digital eye strain because they don't have the right lens prescription, or one that doesn't take into account astigmatism.

Basically, there's no one cause.

Luckily, the symptoms of digital eye strain go away when you give your eyes a proper rest, and studies haven't shown any long-term effects even if you suffer from it regularly.

And if you want to avoid that pain in the first place, doctors recommend you take a 20 second break from your screen every 20 minutes, staring off at an object 20 feet away.

Still, there might be another way screens could harm you, and that's through exposure to blue light that can kill cells in your eyes.

The color of blue light comes from its short wavelength, which also means it has high energy — enough that blue light can damage and eventually kill the cells in your eye's retina.

The light reacts with certain molecules, knocking off bits of them and creating reactive oxygen species, or ROSes, which will bond with almost anything.

They can cause so much damage that cells eventually destroy themselves in a process called apoptosis.

We know this happens because researchers have done a lot of experiments —

not directly on human eyes, of course, but on animal models like rats or human retinal cells grown in petri dishes.

The thing is, most of those studies focus on high-intensity light from LED lamps, and sometimes expose the subjects to that light for day-long lengths of time.

So even though we know that high intensity blue light definitely causes retinal cell death, it doesn't tell us much about the real-life dangers of screens.

There was one 2017 study that looked at the effects of low intensity blue light at three different wavelengths emitted from common types of screens.

Specifically, they found that blue light at 449 nanometers caused the largest increase in those harmful ROSes.

But light with a slightly longer wavelength of 470 nanometers didn't do much damage.

That 21-nanometer change in wavelength might not seem like a lot, but the difference means the two colors of light have different amounts of energy.

The 470 nanometer light, which was a sort of turquoise, just didn't have enough energy to effectively break apart molecules.

This suggests we'd do well to decrease the amount of shorter wavelength blue light from our screens if we want to save our eyeballs.

Don't shut your eyes just yet, because it ignores one major comparison: daylight.

Look anywhere on a clear day and you'll see a lot of blue.

And that blue light is way more intense than what you get from staring at a computer screen.

A paper published in 2016 looked at the amount of light — both in general and in the blue part of the spectrum — from a range of electronic screens and compared it against the amount of blue light you'd be exposed to from simple daylight.

Its conclusion?

The blue light from devices like laptops and smartphones, quote, "does not represent a biohazard, even for long-term viewing."

So you go ahead and watch as many more SciShow videos as you want.

We're officially non-hazardous!

And in the meantime, thanks for watching this episode of SciShow, and thanks especially to our community on Patreon for making this show possible.

We have a whole team of people working to bring you amazing facts and answer fascinating questions every day of the week.

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