It's no secret that we're spending more time in front of screens than ever before.

Canadians say they spend almost 11 hours a day in front of them — at their desks, on their laptops and especially on their smartphones.

But after a long day at work, our eyes often start to feel dry, tired and strained, and many people are desperate for a solution.

Enter blue light filtering lenses. Optical chains say they protect our eyes from blue light emitted from digital screens, and consumers are buying in. And it turns out it's not just eye strain they want to warn us about.

A hidden camera investigation by CBC's Marketplace found sales associates at some of Canada's largest optical chains making "misleading" health claims about blue light from digital screens, but experts say there is no scientific evidence that blue light from computer monitors and screens is harmful.

Staff at four leading chains cautioned buyers that digital screens could damage their retinas and could lead to serious eye diseases such as macular degeneration and cataracts. Two opticians at Hudson's Bay Optical suggested a link to cancer based on an in-store pamphlet provided by lens manufacturer VisionEase , while Vogue Optical's website suggests blue light may increase the risk of " certain types of cancers ."

Hudson's Bay Optical's Glasses Gallery later told Marketplace the pamphlet is "incorrect" and will be pulled from Hudson's Bay Optical stores.

Marketplace visited four major optical chains in Ontario and heard from salespeople who cautioned that digital screens could damage retinas and even lead to serious eye diseases such as macular degeneration. (CBC)

But experts in the fields of optometry and ophthalmology say there's no evidence that blue light from digital screens is harmful.

Dr. Rahul Khurana, a spokesperson for the American Academy of Ophthalmology, said the idea of blue-light blocking is "flawed on so many levels."

"Blue light fear, paranoia, is really out there," said Khurana. "But there's no evidence to show it's truly dangerous and blocking it has not ever [been] shown to [have] any benefits."

Going undercover

Marketplace producers went undercover and visited multiple Hakim Optical, Vogue Optical, Hudson's Bay Optical's Glasses Gallery and LensCrafters locations in southern Ontario to see how the companies market the lenses to consumers.

Several dispensing opticians and salespeople told the producers that blue light from digital screens can lead to fatigue and headaches.

One optician said blue light has "very sharp rays, penetrating at the back of the eyes," while another salesperson said "it tears the eyes right out of you."

Watch Marketplace go undercover at optional retailers:

We went undercover at multiple Ontario locations of these retailers to see how salespeople and opticians are marketing blue light filtering lenses to consumers. 0:59

But more "serious" and even "scary-sounding" to ophthalmologist and macular specialist Dr. Sunir Garg were claims that blue light from digital devices might lead to retinal damage, age-related macular degeneration (AMD) and possibly cancer.

Buying blue light filtering lenses, it was suggested, might eliminate these risks.

"They're introducing this technology that blocks [the digital blue light] out," said one student optician.

Watch "Why you don't need blue light lenses" on Marketplace on CBC-TV on Friday at 8 p.m.

"So we are not going to be seeing things like cataracts or macular degeneration, damage to your retina, things like that."

Many of these claims are also found on Vogue Optical , Hakim , and LensCrafters websites and promotional material.

Dr. Sunir Garg, an ophthalmologist at the Wills Eye Hospital in Philadelphia, reviewed Marketplace’s hidden camera footage and is concerned that optical chains are using scare tactics to sell blue light filtering lenses. (Jeannie Stiglic/CBC)

Marketplace asked Garg, a spokesperson for the American Academy of Ophthalmology and an ophthalmologist at the Wills Eye Hospital in Philadelphia, to review the hidden camera footage.

He was concerned about how salespeople and opticians were "misleading" customers with claims about how the light from screens can damage eyes. Retinal damage and macular degeneration are "serious" claims, Garg said, "but the blue lights from your screen is not the cause of that stuff."

"I think a lot of this is just to create fear and confusion and when people have fear and are confused, they end up spending money on things they don't need to spend money on," said Garg.

Garg's research has led him to conclude that far from benefiting customers, these lenses are mostly benefiting the companies that are selling them.

"Maybe those [blue light filtering lenses] are decisions made in different boardrooms across the country and around the world," Garg said, "but from a science perspective, I don't think people need to worry about this at all."

'Not based on scientific data'

He doesn't blame the staff at these chains for spreading these claims, however.

"I can't fault them [because] I'm sure they're getting a little info sheet that says here's three talking points about blue light-blocking lenses, but it's not based on scientific data," Garg said.

"People will quote that blue light can hurt retinal cells," Garg said, "but what they're not telling you is that it's not been shown in any group of people who are using their screens."

The science into the harms from blue light is mostly done with retinal cells in a petri dish, he said, "or taking a poor mouse and and shining a blue light ray intensely into their eyeball for hours on end."

No evidence lenses are needed

Both Khurana and Garg told Marketplace there's no research that suggests blue light filtering lenses are necessary.

Phillip Yuhas, an assistant professor of optometry at Ohio State University, agrees. He said studies have shown people blink far less during computer use and that blue light filters have not shown any improved "visual comfort" for digital eye strain.

Khurana said if the problem people are having is from digital eyestrain, then blue light filters are doing nothing to address the core issue and "could be doing more harm than good."

Dr. John O’Hagan, an optical radiation expert who works for Public Health England, conducted a study into blue light and found that light levels from digital devices are 'not harmful' and 'considerably below the levels that we experience outside, even in winter.' (Pascal LeBlond/CBC)

But that hasn't stopped eyeglass retailers from promoting them. One optician told Marketplace the blue filter lens is like an "extra shield on top of your eyes to protect your eyes from harmful rays."

The lenses can be purchased with or without a prescription and range in price from $20 to more than $100.

Global sales of the lenses reached $18 million US in 2019, according to Marketwatch.com , and are projected to exceed $27 million US by 2024.

Free and simple solution

Staring at screens for a long time can make eyes feel dry, tired and strained, but blue light is not the culprit, said Garg, and purchasing special lenses won't fix the issue.

"What's bothering [people] isn't the blue light. It's the fact that when they're staring at their screen a lot they're not blinking as often.

"That causes the eye to dry out, [and] when your eyes become dry, they become irritated and scratchy and tired."

To deal with that, he recommends a simple fix. It's called "the 20-20-20 rule." Look at least 20 feet (six metres) away from your screen for 20 seconds every 20 minutes.

Blue light does wake us up and make us more alert, so too much late at night can make it hard to get to sleep. The American Academy of Ophthalmology recommends turning off devices or turning on blue light filters, a couple of hours before going to bed.

Claims not allowed in U.K.

In the United Kingdom, claims like the ones heard in Canada by Marketplace producers aren't allowed.

Opticians and eyeglass retailers risk being fined if they make unproven claims about blue light from digital devices.

In 2015, Boots Opticians were reprimanded and fined 400,000 pounds for making "misleading" claims that blue light causes retinal damage.

Dr. John O'Hagan, an optical radiation expert who works for Public Health England's (PHE) centre for radiation, chemical and environmental hazards, conducted a study on blue light from digital devices on behalf of the organization.

Global sales of blue light filtering lenses reached $18 million US in 2019, according to Marketwatch.com, and are projected to exceed $27 million US by 2024. But experts say that digital blue light isn't harmful and we don't need the lenses at all. (Shutterstock)

He analyzed the amount of blue light coming from various sources including the sky, lightbulbs, mobile phones and computer screens.

"Blue light in our normal environment is not dangerous at all," O'Hagan told Marketplace

"The main source of blue light for us is from the sky and a nice sunny day."

'Not significant'

The PHE study found that for smartphones, laptops and digital devices, the amount of blue light emitted was less than one per cent of the safe exposure leve l, even if stared at all day.

O'Hagan said that the light levels from a smartphone, tablet or laptop are "considerably below the levels that we experience outside, even in winter." We get about 30 times more blue light just by being outside, he said.

"You could stare at your phone all day long, right above the face, and the amount of blue light is not significant," O'Hagan said.

"There is no evidence that blue light from your mobile or other devices is harmful."

Marketplace reached out to the four eyeglass retailers visited by producers.

Hudson's Bay Optical/Glasses Gallery said Marketplace was given wrong information when it comes to cancer and macular degeneration from digital blue light, and says it will be pulling all Vision Ease pamphlets and marketing materials immediately from all stores. It says all staff will be retrained in the coming weeks and it is "committed to providing the very best experience for our customers."

Manufacturer Vision-Ease said they "stand by their marketing materials" and say the science around blue light is "conflicting" and "ambiguous" and more studies are needed.

Canadians say they spend nearly 11 hours each day in front of screens. (Shutterstock/Sjale)

LensCrafters said "while we train our associates on all products, including blue light and blue IQ lenses, some inconsistencies are possible in how individual associates articulate this topic across our stores. We plan to reinforce our in-store training as the awareness around the potential risks of blue light grows."

Vogue Optical said "optical science evolves very quickly" and "there is a high volume of ongoing studies on blue light, some of which point to damaging effects on the eye." They also said they are putting considerable effort into educating staff to help educate consumers about what's available on the market and help them make the best choices.

Hakim Optical says there is evidence that blue light is damaging, and they "will continue to respect and support the licensed optician's obligation to protect and educate the public with all available information and options related to their eye health care." They also said "there is no evidence of harm from the blue-light filter upgrade."

Health Canada to follow up

Health Canada says prescription lenses are regulated through the Medical Devices Regulations and the Food and Drugs Act .

As the Food and Drugs Act "prohibits false, misleading or deceptive advertising of a medical device, such as the promotion of claims without safety and effectiveness data," Health Canada said it will follow up with the optical chains to determine whether medical devices are being advertised or sold in Canada with unsupported health claims.

The Ontario Opticians Association told Marketplace "there is an overwhelming number of clients who have expressed satisfaction with their blue light filters, in that they reduced or eliminated headaches, fatigue, eyestrain and the like."

For people who are concerned about good eye health, Garg has some other suggestions — and they don't include lenses to block blue light.

"Do things like take a break periodically, start quieting down before nighttime, eat a good diet, exercise and not smoke … all those things will help eyes way more than spending money on these blue blocking lenses."