How to choose real sunglasses: UV400, polarised, and the things the label doesn't say
4 August 2026 · 4 min read
First: the filter is invisible
UV protection has nothing to do with how dark the lens is. A clear polycarbonate lens can block 100% of UV, and a fashion-dark lens can block almost none. What you look for is the UV400 mark (blocks up to 400nm, covering UVA and UVB) and the CE mark as a regulated product in Europe.
Why it matters: wearing dark lenses without UV protection makes your pupils dilate behind the tint, letting MORE ultraviolet into the eye than with no glasses at all. Cheap souvenir-stand sunglasses are not neutral — they can be net negative.
Category 0 to 4: how dark is too dark
- Cat 0-1: fashion tints, city dusk, driving at dawn. Not for beach or high mountain.
- Cat 2: medium — everyday Mediterranean use, spring walks, terrace light.
- Cat 3: the standard for real sun: beach, sea, summer driving. Most people should live here.
- Cat 4: extreme (high mountain, glacier). Forbidden for driving — too dark.
Polarised: when it's worth it
Polarising filters kill horizontal glare — the blinding reflection on water, wet roads, car bonnets. For driving at sunrise/sunset, the sea, fishing or skiing, the comfort difference is dramatic. They also show LCD screens differently (car dashboards, phones at certain angles can dim or rainbow): a price most people happily pay, but worth knowing.
Polarised is NOT UV protection: a lens can be polarised and UV-less. You want both labels: UV400 + polarised.
Kids, prescription, and buying well
Children's crystalline lenses let more UV through than adults' — childhood sun exposure is cumulative, and sunglasses at the beach are as necessary as the sunscreen everyone already uses. For prescription wearers, real prescription sunglasses (or photochromic lenses, see that guide) beat clip-ons every time.
Bring your current sunglasses to the optician and we'll check their actual UV filter on our instruments, free and in two minutes. If they pass, great. If not, at least you know what was hitting your eyes.
