Sunglasses with a UV400 rating signifies their lenses will block 99% of ultraviolet light with wavelengths ranging between 100 to 400 nanometres (nm). UV400 rated sunglasses assures they provide crucial protection against UVA, UVB and UVC rays which can otherwise severely damage your eyes. This is the highest level of ultraviolet protection for sunglasses.
Not all sunglasses are UV400 rated but those labelled with the CE or ANSI Z80.3 marking can still provide sufficient UV protection.
For example, sunglasses with the CE mark means the lenses block 99% of UV light up to 380nm in accordance to the European EN 1836:2005 standard.
If you value your vision and general eye safety, this article goes into more detail about the UV400 rating and its importance in your sunglasses.
Let's dive in.
Is UV 400 the same as 100% UV protection?
Yes, UV400 protection is equivalent to 100% UV protection. It means that the sunglasses are able to block out 99% of harmful ultraviolet light with wavelengths up to 400nm. This level of protection is crucial as it covers the entire spectrum of UVA, UVB and UVC rays.
As you'll notice, I keep referring to these sub-types of ultraviolet light and their respective wavelengths. This is because their frequency (in nanometres) is what makes them both harmful and invisible. To get a better understanding of UV light, check out the brief but helpful description below.
What is UV light?
UV light is a type of solar radiation produced by the sun and some artificial sources, like tanning beds. Unlike visible light (also from the sun), UV is completely invisible which more easily penetrates your eyes thus posing more risk towards your general eye health. UV light can can be divided into three sub-types based on their wavelengths: UVA, UVB, and UVC rays.
UVA emits the least energy, can lead to skin aging. It is often associated with wrinkles and "sunspots" as common long-term effects. Moreover, it has a connection to certain skin cancers.
UVB emits slightly more energy than UVA, causing damage to your skin and bodily tissue. It's responsible for causing sunburn and most UV-related cancers.
UVC emits the most energy but is thankfully absorbed by the Earth’s atmosphere. UVC easily penetrates the skin with a strong risk towards skin cells and your eyes.
The effects of UV radiation on the eyes
There are various eye conditions related to UV exposure that can impact our vision and overall eye health. Common symptoms include
Photokeratitis: Often referred to as a "sunburn of the eye", "snow blindness" or "welder's flash", photokeratitis is a painful condition caused by short-term exposure to UV rays reflected off sand, water, or snow. Symptoms include red eyes, a gritty feeling in the eyes, extreme sensitivity to light, and tearing.
Cortical Cataracts: UV light, particularly UVB rays, can accelerate the development of cortical cataracts, characterized by white, wedge-like opacities that start in the periphery of the lens and work their way to the centre in a spoke-like fashion. This condition can lead to significant vision impairment.
Pinguecula and Pterygium Development: Extended UV exposure can lead to the formation of pinguecula and pterygium on the eye surface. These growths can potentially cause discomfort, blurred vision, and cornea alteration, impacting vision quality.
Increased risk for Age-related Macular Degeneration (AMD): Long-term UV exposure may escalate the risk of developing age-related macular degeneration, a leading cause of vision loss among older adults. AMD deteriorates the macula, diminishing central vision and the ability to see fine details clearly.
Each of these effects underscores the critical importance of protecting the eyes from ultraviolet rays through the use of UV protective sunglasses, wide-brimmed hats, and UV-blocking contact lenses.
How do you tell if sunglasses are UV 400?
When purchasing new sunglasses, they often come with a small temporary label/sticker on the lenses stating the lenses are UV400 rated or 100% UV. In other cases, some brands or manufacturers may provide a printed leaflet stating the sunglasses' UV protectivity. This information may also be stated online via a sunglasses vendor's website.
But what about older sunglasses?
How to test your sunglasses for UV protection at home
It's difficult to know if sunglasses are precisely UV400, but you can check for basic UV filtration using the handy guide below;
- Shine a UV torch on a (real) bank note to illuminate it's fluorescent markings.
- Darken the room you're in.
- Place the sunglasses directly over the bank note on a table.
- Shine the UV torch through one of the sunglasses' lenses
- If the banknote doesn't illuminate the same fluorescent markings, it means your lenses are UV protective.
- Repeat the process for both lenses.
This is just a quick test and may not always be accurate, so if you're still unsure about your sunglasses' UV protection, it's best to have them professionally tested using the method below.
How to accurately know if your sunglasses are UV400
The most accurate way to know if your sunglasses have UV400 protection is to take them to a local optician. There, they can test your lenses using a specialised UV light meter called a photometer. In most cases, you won't be charged for this service. But if you are, it will only be a small fee for reassurance your eyes are safe.
What is the highest UV protection in sunglasses?
UV400 is the highest protection level that sunglasses can provide. This means that they block 99-100% of UVA, UVB and UVC rays to a maximum wavelength of 400 nanometres (nm). UV400 rated sunglasses actually exceed British (UKCA) and European (CE) standards which block UV up to 380nm.
Regardless of UV400 labels, legitimate sunglasses should at least bear the CE marking on the frame itself. This internationally recognised symbol indicates that the frame conforms to the European standard EN 1836:2005, typically marked on the interior surface of one of the temples (arms).
UV400 sunglasses will always at least bear the CE mark in addition to any 'UV400' or '100% UV ' labels, stickers or tags attached to the frame. CE markings are required by law for sale or distribution within the European Union whereas UV400 labels aren't.
Is UV 400 category 4?
No. UV400 and lens category 4 mean different things. UV400 blocks invisible UV light up to 400nm whilst lens category 4 refers to lens darkness which absorbs visible light. There are five sunglasses lens categories in total, ranging from 0 (very light) to 4 (very dark) which are categorised by their absorption percentage (ABS%).
The higher the ABS%, the darker the sunglasses will be. See the table below as a reference.
|
Category |
0 |
1 |
2 |
3 |
4 |
|
ABS% |
0% - 10% |
10% - 20% |
20% - 43% |
43% - 85% |
85% – 92% |
|
Tint |
Very light |
Light |
Marginal |
Dark |
Very dark |
|
Sun use |
Overcast |
Low |
Moderate |
Strong |
Very strong |
|
Driving suitability |
Day & night |
Day only |
Day only |
Day only |
Never |
Are darker sunglasses better for your eyes?
No. Sunglasses with very dark lenses provide no more UV protection. Dark lenses simply absorb more visible light which can aid visual comfort if you suffer with light sensitivity (photophobia) or for extreme exposure scenarios such as high-altitude mountaineering.
As seen in the table above, very dark sunglasses lenses (category 4) aren't suitable for driving. In fact, it is illegal in the UK wear sunglasses with lenses darker than 85% ABS whilst driving.
Sunglasses category doesn't influence UV protection. Their darkness (ABS%) is purely a method to absorb more visible light as an option to control your visual comfort.
To be classified as UV sunglasses, the lenses must block 75% to 90% of visible light and block 99% of UVA and UVB radiation.
Most sunglasses are fitted with category 3 lenses with an average of 80% to 85% ABS.
Do cheap sunglasses have UV protection?
Yes. Cheap sunglasses can indeed have UV protection, as long as they're legitimately CE marked or come with a UV400 rating. Despite poor quality components and materials, their lenses are arguably the most important feature which must provide basic ultraviolet protection.
Investing in good quality sunglasses from a reputable source helps avoid the risks of illegitimate, non-UV protective lenses. Black market or 'knock-off' sunglasses can actually be worse than no sunglasses at all.
Behind dark lenses, your pupils dilate to let more light in. Ironically, this leaves them even more exposed to UV light. A sinister prospect as you could be unknowingly damaging your eyes.
Can you drive with UV400 sunglasses?
Yes. As long as your sunglasses aren't too dark (i.e. category 4) UV400 sunglasses are perfectly safe and great for driving. Car windshields don't effectively block all ultraviolet light therefore UV sunglasses will keep your eyes safe. Furthermore, sunglasses reduce the amount of visual strain put on your eyes which makes it easier to see oncoming hazards on bright days.
For even greater visual performance, polarised sunglasses can be especially helpful for driving. In addition to UV protection, they contain an additional lens layer which eliminates glare from wet roads or other cars.
Over long durations of visual focus (big car journeys) polarised lenses drastically reduce the effects of visual fatigue. Non polarised lenses don't glare as effectively which subconsciously makes you strain to focus on the road ahead.
Does polarised mean UV protection?
No. UV protection is mandatory for eye health. Polarisation is optional and means the lenses contain an additional filter called a polariser that diminishes reflected glare. Polariser filters don't block invisible UV, but instead can block visible light which has been reflected from flat surfaces such as water, snow or ice.
Glare occurs when visible sunlight bounces off reflective surfaces, becoming condensed and horizontally orientated. In this state, the light is highly concentrated and blinding to look towards.
To combat this, polarised sunglasses lenses contain a film which hosts rows of closely-packed, microscopic, vertically aligned molecules. These rows block the horizontal orientated light waves from passing through the lenses, thus making your vision glare-free.
Combined with UV protection, polarised lenses are widely deemed as a superior option. They provide more consistent vision, greater visual acuity, colour and depth perception. This is why they're very popular for driving and water sports such as fishing.
Summary
- UV400 sunglasses block 99% of ultraviolet light
- The highest UV protection for sunglasses is UV400.
- The name UV400 refers to the lenses capacity to block solar radiation with wavelengths between 100nm to 400 nm.
- UV400 means the same as 100% UV.
- UV light is a type of solar radiation made of UVA, UVB and UVC light waves.
- UV radiation can lead to eye conditions such as photokeratitis, cataracts, pinguecula and pterygium growth, and an increased risk for age-related macular degeneration.
- Polarisation is a secondary and optional upgrade to filter visible light by reducing glare from flat reflective surfaces such as water or wet roads.
- Polarised sunglasses are particularly beneficial for water sports and for driving.
Hopefully you found this article helpful. If so, please check out our other sunglasses blog posts for more helpful advice.
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