By Stephanie Stahl

PHILADELPHIA (CBS) — You’ve heard about the dangers linked to blue light emitted from computers and phones, but experts say it isn’t all bad. It’s kind of a mixed bag when it comes to blue light.

While it’s not good to be constantly starting at screens, doctors say blue light in limited doses can be therapeutic.

We spend hours a day on computers and looking at phones. Doctors warn excessive exposure to blue light can be bad for your eyes and brain.

“A lot of the talk about blue light is digital eye strain and how it can affect sleep while on digital devices late at night,” ophthalmologist Dr. Melissa Barnett.

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But research shows blue light has some benefits too, including boosting alertness, improving memory and cognitive function and elevating your mood.

“It helps your natural rhythm, so you sleep, wake cycle, and it also can prevent nearsightedness,” Barnett said.

Experts say it’s important to remember blue light doesn’t just come from computers and phones.

“The most common source of blue light is sunlight. Blue light is also in florescent light, street lights and screens,” Barnett said.

For people who are concerned about blue light dangers, there are now all kinds of blue light blocks, including glasses and contact lenses with built-in UV protection.

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Even with protection — and especially without — doctors recommend taking regular breaks from your screen time.

“It’s really important to know when you’re on digital devices all day long, to take breaks every 20 minutes to look away at something that’s not digital,” Barnett said.

Doctors say it’s especially important to not get too much exposure to blue light right before bed. It’s been scientifically proven to suppress melatonin, which can interfere with being able to fall and stay asleep.

Stephanie Stahl