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UV400 turns up on sunglasses tags so often it can start to feel like decoration. It sounds reassuring. It also sounds vague. In plain terms, it’s a statement about ultraviolet protection.
Ultraviolet light sits beyond the visible spectrum. You can’t see it, but your eyes still absorb it. Over time, that exposure is linked with issues such as cataracts and other forms of long-term damage, which is why protection matters even when the day doesn’t feel particularly bright.
A quick note on UVA and UVB
Ultraviolet radiation is usually described as UVA, UVB and UVC. UVC is largely filtered out by the atmosphere. UVA and UVB reach us.
UVA is present all year, including on overcast days, and penetrates more deeply. UVB is more intense and tends to peak in summer and at higher altitudes. Both contribute to cumulative exposure.
When a lens is labelled UV400, it means it blocks ultraviolet wavelengths up to 400 nanometres. That covers UVA and UVB. In real-world terms, it’s a shorthand for full UV protection.
Dark lenses aren’t automatically safer
A common assumption is that darker sunglasses protect better. Tint and UV filtering are separate things.
This matters because dark lenses without proper UV protection can be actively unhelpful. Shade makes your pupils open wider. If the lens isn’t filtering UV, more of it can reach the eye than it would without sunglasses at all.
So UV400 is a functional standard, not a style cue. A pale tint can be just as protective as a dark one, if the lens is made properly.
How it’s measured
UV400 isn’t a poetic promise. It’s a measurement taken with testing equipment that checks how much UV passes through a lens across different wavelengths.
In the UK and Europe, sunglasses should meet recognised standards for UV protection. A UV400 marking usually indicates protection across the full ultraviolet range, though the label on its own doesn’t tell you much about how carefully a product is made or checked.
Where designer sunglasses fit in
People sometimes treat “designer” as purely cosmetic. In practice, most established brands don’t ignore basic optical requirements, particularly for something worn in full sun.
With Versace sunglasses, for example, UV400 protection is generally part of the lens specification rather than an optional add-on. That means you can choose a dramatic shape or heavier tint without having to trade off the underlying purpose of sunglasses.
It’s also worth saying that UV protection doesn’t usually “wear out” quickly. In many cases it’s built into the lens material itself, not applied as a surface layer.
Everyday exposure adds up
UV damage isn’t reserved for holidays. It accrues in small doses: walking to the station, sitting outside on a bright winter afternoon, long drives with light coming in at an angle. The sun can be low and still harsh.
That’s why UV400 matters for day-to-day wear, not just in heatwaves. The protection is doing quiet work in the background.
What UV400 doesn’t tell you
UV400 is a baseline. It doesn’t speak to glare, comfort, or how the world looks through the lens.
Polarised lenses reduce glare from roads, water and other flat surfaces, but polarisation is separate from UV protection. A lens can be polarised without blocking UV properly, and it can block UV without being polarised.
Lens colour is similar. It affects contrast and how your eyes feel after a long day outside, but it doesn’t determine whether UV is being filtered.
UV400 isn’t a buzzword worth obsessing over. It’s simply the minimum you want a lens to do properly. Once that box is ticked, the rest comes down to fit, comfort, and what you actually like wearing.