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Blue light glasses test: How well do your blue light glasses work?

Blue light blocking glasses can provide a big step toward reducing digital eye strain and improving your quality of sleep.

But different “blue light glasses” block different amounts of blue light. And there currently are no standards that say how much blue light these glasses should filter to keep your eyes comfortable and safe.

This article will help you make sense of what to look for and what to expect when shopping for blue light glasses.

Blue light glasses: The basics

Generally, blue light glasses with clear lenses block up to 20% of blue light, while blue light glasses that have a yellow or amber tint tend to block more blue light than those with clear lenses. 

Some blue light glasses with orange or other specialty tints can block nearly 100% blue light, but these lenses significantly affect your color vision as well. 

But it’s important to know that all blue light is not equal. The term “blue light” encompasses a broad range of high-energy visible (HEV) light with different wavelengths and amounts of energy. 

The energy of visible light (including HEV blue light) is determined by its wavelength, which is measured in nanometers (nm). 

The entire blue light spectrum includes HEV light with wavelengths ranging from 400 to 500 nm. Shorter-wavelength (400 to 450 nm) blue light has more energy than longer-wavelength (451 to 500 nm) blue light. It’s more important to protect your eyes from this highest-energy portion of the blue light spectrum — sometimes called violet-blue light — as this appears to be more potentially damaging to the eye than blue light with longer wavelengths (and less energy).

So, it’s actually more important to know what type of blue light your glasses are protecting you from, rather than the percentage of total blue light being filtered by them.    

SEE RELATED: Should I buy blue light glasses for my kids?

How blue light glasses are tested

You can find virtually anything on the internet — including easy at-home ways to test your blue light glasses. 

These online blue light tests might be useful to check if tinted lenses block nearly 100% of blue light, but they aren’t sensitive enough to measure the blue light-filtering capacity of clear (or only lightly-tinted) blue light glasses that most people prefer. 

The only proven way to accurately test blue light glasses is with an instrument called a spectrophotometer (also called a visible spectrometer).

A simplified diagram of a spectrophotometer.

A spectrophotometer in a laboratory instrument that splits light from a full-spectrum visible light source into its component wavelengths (usually in 10-nm increments). A lens or other optical sample is then placed in the machine, and a detector in the spectrometer determines the exact amount of a specific wavelength or range of wavelengths of blue light that is transmitted or blocked by the lens.

Unfortunately, a laboratory-grade spectrophotometer is an expensive piece of equipment that’s not typically found in an eye doctor’s office or eyeglasses store. So eye care professionals usually must rely on technical marketing materials from lens manufacturers to determine how much blue light (and which wavelengths of blue light) are blocked by blue light glasses.

How much blue light blocking is enough?

Currently, there are no national or international standards concerning how much blue light should be blocked by “blue light glasses” for safety or comfort.

But because people today spend so much time in front of blue light-emitting screens of computers and phones, they are being exposed to significantly more blue light than previous generations. This has many eye doctors and researchers concerned.

The challenge for lens manufacturers and eye care professionals alike is that market research has shown people prefer to wear glasses with clear lenses rather than glasses with tinted lenses.

Blue light-filtering glasses with clear lenses can block up to about 20% of blue light. That might not sound like much, but most of the blue light these lenses block is in the high-energy violet-blue range (400 to 450 nm), which is the most likely to be damaging to the eye.

One example of these lenses are Eyezen lenses.

Who should wear blue light-blocking glasses

Given that people are being exposed to more blue light than ever before and the long-term health effects of this increased exposure from electronic devices is still unknown, a strong case can be made that anyone who spends more than a few hours per day looking at screens should wear lenses that block some degree of blue light.

At a minimum, blue light-blocking glasses can make your screen time more comfortable and decrease your risk of digital eye strain.

Often, 10% or 20% blue blocking is all you need to notice a significant improvement in visual comfort during hours of screen use, and this may be sufficient to protect your eyes from potential long-term damage. Also, some longer-wavelength blue light is good for you during the day, as it helps keep you alert.

People who suffer from more debilitating conditions like frequent headaches or ocular migraines might want to consider a higher degree of blue light protection.

One thing that's all but guaranteed to strain your eyes is an out-of-date eyeglasses prescription

If you wear prescription glasses, always keep your lenses current with regular eye exams. Whether you intend to buy prescription blue light glasses or not, maintaining 20/20 vision is the perfect way to kickstart your journey toward eliminating eye strain.

SEE RELATED: Learn more about computer vision syndrome

Consult your eye care professional

Because there’s no feasible way of knowing if marketing claims for blue light-blocking glasses are true or backed by standardized blue light testing, the best way to protect yourself when buying computer glasses is to seek the advice of an experienced eye care professional.

Purchasing Eyezen or another reputable brand of blue light-blocking lenses from your eye doctor or optician provides a greater degree of quality assurance than purchasing an unknown brand of computer glasses online. 

SEE RELATED: Other ways you can reduce eye strain

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