Do Promo Sunglasses Protect You From UV Light?

Why UV Protection Matters In Sunglasses

Quick refresher on high school physics. UV light is ultraviolet light. It’s invisible to humans, but a surprisingly varied range of animals can see it, including birds, bees, mice, and reindeer. (No idea how someone worked that out.) It has shorter wavelengths than the light we can see, which means it also has higher energy. That’s the dangerous bit.

The magic label to look out for when you’re buying sunglasses is UV400. This means they’ll block at least 99% of UV rays with wavelengths up to 400 nanometers (nm). That’s just a fancy way of saying all the UV light that reaches you on the Earth’s surface.

There are three classifications of UV light, based on wavelengths:

You already know UV light can cause sunburn (ouch) and skin cancer (mega ouch) – and it’s not great for your eyes either. According to the National Eye Institute at the National Institutes of Health (NIH), and the American Academy of Ophthalmology, UV light can cause:

Age-Related Macular Degeneration (AMD)

This affects the center point of your vision – imagine a blurry spot right in the middle of where you’re looking.

Cataracts

Blurring of your eyes’ lenses, which in turn makes your vision appear cloudy, like a camera that’s out of focus.

Pterygium

Growths on the top layer of your eyeball that if left untreated can block the cornea and impact vision.

Skin cancer

As with the rest of your skin, UV light can cause cancer on your eyelids – typically basal cell carcinomas, which are usually treatable if caught early, but you so don’t want to deal with that.

Photokeratitis

Like sunburn on your eyeballs – yikes. Temporary but painful. Often afflicts people in snowy areas or around water, where reflections increase the amount of UV light entering the eye.

As you can see, protecting your eyes from UV light is as important as protecting the rest of your skin.

Method

1. 1

   Turn the lightmeter on and zero it.

2. 2

   Put the right lens in front of the lightmeter.

3. 3

   Place the UV light directly on the right lens and turn on.

4. 4

   Record light meter reading.

5. 5

   Repeat for the left lens.

6. 6

   Take average lightmeter reading across both lenses.

How We Calculated Our Results

We used milliWatts per centimeter squared (mW/cm2) as our unit of measurement.

A Watt (W) is a measurement of how much energy is transferred during one second. For example, light bulbs are rated by how many Watts they use to create light, so a 40W bulb uses 40W a second. A milliWatt is 1/1000th of a Watt, because that’s the metric system, baby! In effect, we measured how many milliWatts were transferred over a 1 centimeter square per second.

To get a baseline we could use to judge how well or not well our sunglasses blocked the UV light, we shone the light directly on the lightmeter and recorded the reading as 7.58 mW/cm2. We then took the average of how much light both lenses allowed through, and used this to calculate the percentage of light the sunglasses blocked.

Results

All our sunglasses blocked over 99% of the UV! Four out of 10 blocked 100%.

If we’re being honest, there are two reasons that this isn’t exactly a surprise. Number one is that sunglasses are regulated as medical devices by the Food and Drug Administration (FDA), which means they have to live up to the claims they make about blocking UV light. So if they say UV400, they must block at least 99% of UV rays.

Second, all the sunglasses we tested have plastic lenses. Plastics like polycarbonate and some acrylics are very good at blocking UV light without needing any extra treatments or films. They’re even better at it than glass, which blocks UVB but not all UVA. However, another popular plastic used to make lenses – CR-39 – doesn’t block UV light, so seeing plastic lenses isn’t a guarantee of UV protection. Make sure you always look for that UV400 label.

While we’re all here, chatting about sunglasses, the color or darkness of the lenses on plastic sunglasses has nothing to do with how much UV light they block. Dark lenses don’t block more UV than clear lenses, and vice versa. UV light is invisible to humans, so unless you’re a reindeer, you can’t see the difference between sunglasses that block UV light and those that don’t.

Key Takeaway

Normally we have loads of takeaways, but this time there’s only one and it’s this: When it comes to sunglasses, a designer name – and high price tag – does not mean better UV protection. A pair of promo sunglasses rated UV400 and a pair of designer sunglasses rated UV400 are both legally required to block at least 99% of UV light.

Conclusion

The first thing to look for when buying new sunglasses is the label UV400, since this means your sunglasses will actually block dangerous UV light. All sunglasses sold in America are regulated as medical devices by the FDA, so the only difference between a promo and designer pair is how annoyed you’ll be when you lose them. (Because obviously, our promo sunglasses are way cooler.)

Q#	UV light allowed through right lens (mW/cm2)	UV light allowed through left lens (mW/cm2)	Average UV light allowed through both lenses (mW/cm2)	Percentage of UV light blocked	Watch Experiment
Q15113	0	0	0	100%	View Product
Q23071	0.01	0.01	0.01	99.87%	View Product
Q36679	0.02	0.01	0.015	99.8%	View Product
Q49871	0	0	0	100%	View Product
Q51545	0	0	0	100%	View Product
Q70191	0	0	0	100%	View Product
Q70219	0.03	0.02	0.025	99.67%	View Product
Q70979	0.06	0.05	0.055	99.27%	View Product
Q71109	0	0.01	0.005	99.93%	View Product
Q71115	00.01	0.01	0.01	99.87%	View Product