There's a photo of me at 22 that I show to nobody. July 2014, the Malsaucy peninsula, the Eurockéennes festival in Belfort — the festival that converted me. I'm wearing frayed denim shorts, a fabric wristband already stiff with dried mud and, on my nose, a pair of tiny round sunglasses with mirrored lenses (pink, yes). Bought for next to nothing from a stall a few steps from the entrance. It's about 4pm. The sun is beating down on the lake, and I'm squinting behind my two pink discs as if they weren't there.
In the photo (taken by a friend from those days), that's all you see: two little circles lost in the middle of a rather long face, which they stretch even further. I look like the poster for a spy-film parody. That evening my eyes stung and I had a headache — which I put down to the sun and the warm wine. Did those lenses filter anything at all? I'll never know. No marking on the arm, no leaflet, no category. Fancy-dress glasses sold as sunglasses.
Eleven years later, that photo sums up the two mistakes most of us make in June (me first). We pick a frame because it's on trend, without checking what it does to our face. And we pick lenses by their colour, assuming that the darker they are, the better they protect. No. A pair of sunglasses is two choices in one: the frame for your face, the lenses for your eyes. Here are both methods — reading the inside of an arm the way you'd read a care label, then finding your face shape in front of a mirror.
Frame and lenses: why sunglasses are two separate choices
Sunglasses are two objects screwed together. The frame handles style and comfort — it shapes your face, it stays put on your nose (or doesn't), it covers more or less of the sides. The lenses do the invisible work — they cut glare and they block ultraviolet light, two jobs that have nothing to do with each other.
This is the bit everybody misses. The College of Optometrists' advice on choosing sunglasses calls the idea that darker lenses protect more a common misconception. The tint you see in the mirror tells you nothing about what's reaching your retina.
And the price? It tells you nothing either: a laboratory test of 57 pairs shows it, and I'll come back to it further down. What your money really buys is the frame: its material, its hinges, its finish, and the way it suits you.
The result: we'll take things in order. Lenses first, because a perfect frame with poor lenses is still a poor pair. Then your face — because a pair that protects but lives at the bottom of your bag protects nothing at all.
Reading the inside of the arm: CE or UKCA, category, BS EN ISO 12312-1
Sunglasses count as personal protective equipment — like a climbing helmet, yes. In Great Britain they can carry either the CE mark or the UKCA mark. The government's guidance on personal protective equipment explains that regulations in force since 1 October 2024 extend recognition of the CE marking indefinitely in GB, so businesses can use either marking.
The reference standard is BS EN ISO 12312-1 — the one for sunglasses for general use. The NHS page on sun safety recommends sunglasses "with the CE Mark and British Standard Mark 12312-1:2013 E", ideally with wraparound lenses or wide arms. According to the factsheet from the Swiss Federal Office of Public Health (FOPH), the label must also show who made or supplied the pair, the filter category and whether it's suitable for driving. Pairs that aren't carry the symbol of a crossed-out car.
In real life, you'll mostly find three things printed inside an arm. The CE (or UKCA) mark. The category (often "Cat. 3", sometimes just a "3"). And, with a bit of luck, "UV400". Many frames also show three numbers, something like 52□18 140 — the width of one lens, the width of the bridge (the bit that sits on your nose) and the length of the arm, in millimetres.
What about the leaflet? You've probably never read one, and you're not alone in that. In the FOPH test, the information supplied to the wearer was "frequently incomplete" — and not a single leaflet warned against wearing the glasses to drive at night or at dusk.
Filter categories 0 to 4: what they really measure
The category measures one thing only: how much visible light the lens lets through. It's a glare scale, not a UV scale. The standard sorts lenses into five categories. Here are the thresholds from the FOPH factsheet on sunglasses for general use, published in October 2024, with the uses it recommends.
| Category | Visible light let through | Tint | Recommended use |
|---|---|---|---|
| 0 | Over 80% | Barely tinted | Not suitable as sunglasses |
| 1 | 43 to 80% | Light | Not suitable as sunglasses |
| 2 | 18 to 43% | Medium | Everyday use |
| 3 | 8 to 18% | Dark | Everyday use, holidays, beach, mountains |
| 4 | 3 to 8% | Very dark | Extreme glare (sea, desert, high mountains, snowfields). Never for driving |
Read the second column the other way round. A category 3 lens stops between 82 and 92% of visible light; a category 4, up to 97%. A very dark lens without a proper UV filter is still possible — which is exactly why the mark and the UV wording matter as much as the tint.
If the lenses on your favourite pair are barely tinted, check the arm. A category 0 or 1 looks lovely in a portrait — and is properly useless in a beer garden on the one scorching Saturday of June.
Which category of sunglasses: city, beach, mountains, driving
For a "normal" British summer (the city, a pub garden when the weather allows, a weekend by the sea), the answer comes down to two numbers. The FOPH recommends a category 2 or 3 for everyday wear, and keeps category 4 for extreme conditions — with side protection.
- In town, at work, in the park: category 2 if you live in the shade of tall buildings, category 3 if you eat your lunch in the sun.
- At the beach, by a lake, on a boat: category 3. Water and sand bounce the light back at you, and the NHS favours wraparound lenses or wide arms.
- High mountains, snow, a whole day at sea: category 4, with side protection (a requirement for this category, according to the FOPH).
- Driving: category 2 or 3. Never 4.
Why never 4 behind the wheel? The FOPH is blunt: these lenses are too dark to recognise traffic light signals. It adds that no sunglasses are recommended for driving at night, at twilight or in poor light. The Highway Code's rules for drivers say the same thing in British: "At night or in poor visibility, do not use tinted glasses, lenses or visors if they restrict your vision." And rule 93 is worth remembering too — slow down, and stop if necessary, if you're dazzled by bright sunlight.
My everyday pair is a category 3. It covers pretty much everything I do from April to September, from London Fields to weekends by the sea. If you only buy one pair, make it that one.
UV400 and "100% UV": the protection you can't see
UV protection depends on what the lens is made of — not on its colour. The FOPH says so in black and white: the degree of UV protection depends on the lens material, "and not on the colour or tint of the lenses". Sunglasses with the CE mark labelled "100% UV" or "UV 400" filter out UVA and UVB. As defined in the standard, a lens offers 100% UV protection if it lets through less than 0.05% at wavelengths up to 380 nanometres.
Moorfields Eye Hospital's advice on looking after your eyes in the sun is just as clear: always look for the UV 400 mark, and look for the CE mark. It also warns that fake sunglasses often provide little or no protection from the sun.
Why should you care at 25 or 30? Because UV damages eyes without warning. The College of Optometrists notes that ultraviolet light can cause cataracts and may be linked to macular degeneration. The FOPH describes two stages: intense or prolonged exposure can cause painful inflammation of the cornea or retina, and cataracts, retinopathy or age-related macular degeneration can develop over time.
Two details in the FOPH factsheet made me raise an eyebrow. First: in children and adolescents, a narrow "window" lets some UV (around 320 nm) reach the retina — and it only closes by the age of 30. Second: using sunglasses badly can even increase the dose your eyes receive, through dilated pupils or longer stretches outdoors without proper protection. A Moorfields consultant ophthalmic surgeon makes the same point about imitation lenses: if they don't filter UV and your pupils dilate behind them, more UV can get into the eye. My pink discs of 2014 ticked the second box at least: a whole afternoon in full sun behind lenses that said nothing about UV.
One more point from the FOPH: light-coloured eyes, with less pigment in the iris, let UV in more easily than dark eyes. Nobody's excused from protecting themselves — but if your eyes are blue or green, UV400 isn't optional.
Find your face shape in five minutes in front of a mirror
A word of warning first: "face shapes" are a stylist's shorthand, not a science. Most faces are a mix — a bit oval, a bit square. The point isn't to label you, but to spot three things: whether your face is longer than it is wide, where its widest part sits, and whether it has angles.
The easiest method fits in a bathroom.
- Tie your hair back. Your forehead and jaw need to be completely clear.
- Stand facing the mirror, far enough back to see your whole face, and keep still.
- With an old lipstick (or a kohl pencil), trace the outline of your face on the mirror, from your hairline down to your chin.
- Step back. Compare length and width, then your forehead, cheekbones and jaw.
You'll usually end up with one of these seven shapes.
- Oval: longer than it is wide, widest at the cheekbones, rounded forehead and chin.
- Round: almost as wide as it is long, full cheeks, few angles.
- Square: almost as wide as it is long, broad forehead, broad and angular jaw.
- Long (or rectangle): clearly longer than it is wide, with forehead, cheekbones and jaw of similar width.
- Heart: broad forehead, narrow chin, often pointed.
- Triangle: jaw wider than the forehead.
- Diamond: wide cheekbones, narrow forehead and chin.
Mine is long (that photo leaves no doubt). Clearly longer than it is wide, with a forehead, cheekbones and jaw of almost the same width. Hence the disastrous effect of those little circles in 2014 — they stretched the whole thing out like an El Greco portrait.
Which sunglasses frame for which face shape
The basic rule fits in one word: contrast. A frame balances a face when it brings what the face lacks. Angles for a round face, curves for a square one — width for a long one. It's the same logic as our guide to dressing for your body type, applied to a few square centimetres.
| Face shape | Frames that balance it | Frames that flatten or stretch it |
|---|---|---|
| Oval | Almost all: square, butterfly, aviator, round | Very large frames that overhang the face |
| Round | Rectangular, trapeze, upswept cat-eye | Small round frames, narrow frames |
| Square | Round, oval, aviator, soft-cornered butterfly | Chunky square frames, thick geometric shapes |
| Long | Deep frames, oversized, thick arms | Small, narrow frames |
| Heart | Aviator, round, frames that are light at the top | Very upswept cat-eye, heavy top bars |
| Triangle | Cat-eye, browline frames | Bottom-heavy frames |
| Diamond | Oval, soft cat-eye, rimless | Narrow frames that emphasise the cheekbones |
A round face loves anything that draws a clean horizontal line — the trapeze shape (the one made famous by Ray-Ban's Wayfarer) works almost every time. A square face softens with curves: the aviator, with its teardrop dipping towards the cheek, breaks up the jawline. A heart face wants weight lower down, to balance a broad forehead. The triangle is the opposite — you want a strong top bar, like browline frames where only the upper rim is thick.
A long face (mine, then) needs depth in the frame and width at the sides. My current pair: a square acetate frame in grey-toned tortoiseshell, deep enough to sit just under my brows. Its slightly chunky arms widen the face at the temples (the same trick as earrings that stop at jaw level).
Now for the truth the charts leave out. You're allowed to wear a "forbidden" shape. You love small round frames and you've got a round face? Wear them. A "wrong" frame worn with confidence suits you better than a "perfect" one you feel dressed up in. I'll be blunt: a chart saves you time in the shop — it doesn't get to decide who you're allowed to be.
Frame size before frame shape: brows, width, nose
A frame in the right shape but the wrong size won't suit you. And this is where style and protection meet. The FOPH says sunglasses should fit well, with lenses that "extend up to your eyebrows and cover the width of your face". The reason is simple — gaps between the frame and your face let in direct sunlight, light reflected off the ground and scattered light. Hence its advice to go for wraparound styles, and the NHS's preference for wraparound lenses or wide arms.
Stylists say the same thing for different reasons. A top rim that follows your brow line gives you a clean, defined look. A frame as wide as your face at the temples balances it. Your four in-shop tests:
- Brows. The top of the frame follows their line — without hiding them completely, without leaving a big gap above.
- Width. The arms don't squeeze your temples and don't splay out. From the front, the frame doesn't overhang your face by much.
- Cheeks. Give a big smile (a real one, teeth and all). If the frame lifts off as it hits your cheeks, it's too big or sitting badly.
- Nose. Tip your head down towards your feet (as if you were tying a shoelace). If the glasses slide, the bridge is too wide for you.
Buying online? Dig out the three numbers printed inside the arm of your favourite pair (lens, bridge, arm). Those are your reference points. A new frame within a few millimetres of them has a good chance of fitting like the old one — even in a different shape.
Frame colour and lens tint: your skin tone first, your eyes second
You choose a frame colour the way you'd choose a top worn close to your face. If you've already done the at-home colour analysis to find your best colours, you have the essentials. A cool undertone works with black, grey, navy or grey-toned tortoiseshell — a warm undertone with honey tortoiseshell (the warm, amber kind), brown, olive green or gold metal. My own test put me in cool undertone, soft intensity: glossy black makes me look harsh, grey tortoiseshell suits me.
For a metal frame, the logic is the same as for jewellery — gold or silver depending on your undertone, and on the earrings you already wear. Our guide to choosing and matching jewellery covers this game of metals, and it applies just as well to a pair of aviators.
Lens tint, on the other hand, affects how you see. The FOPH rates brown or grey tints as ideal for visual clarity, and warns that blue and red tints impair contrast sensitivity and sharpness of vision. My pink mirrored lenses of 2014 — exactly what not to do.
As for lens treatments, three names come up in shops.
- Polarised: the FOPH explains that these lenses have a special coating that filters and absorbs reflected light, reducing glare and eyestrain even further. Brilliant by the water. It is not UV protection in itself.
- Photochromic: lenses that change colour according to light conditions — the College of Optometrists mentions them as an option for glasses wearers.
- Gradient: darker at the top, lighter at the bottom. Handy for reading on the beach without being dazzled when you look up.
One last style point: sunglasses work with everything you wear near your face. A silk square tied as a headband, a cat-eye pair — and you've got a 1960s Riviera look in thirty seconds. The knots are all in our guide to tying a silk scarf.
Cheap, designer or fake: where to buy sunglasses
The FOPH test is good news for your bank balance. Of the 57 CE-marked pairs, bought in shopping centres, specialist shops and online, all met the requirements for 100% UV protection — and the most expensive and cheapest models showed no difference in optical quality. The Moorfields consultant says much the same on camera: "By that I don't mean an expensive design pair but a pair that are safe and effective."
Not everything was perfect: two adult pairs didn't meet the category they claimed, and user information was often incomplete. But the real risk isn't the cheap pair from a reputable shop. It's the pair with no marking — the festival stall, the beach seller, the unknown marketplace listing, the knock-off of a big brand. A fake answers to nobody about what its lenses filter.
So where should your budget go? My view: into the frame that suits you, not into the logo. A good hinge (sprung, ideally), thick acetate, lenses that survive a day on the pebbles. That's what justifies a price. UV protection comes at every price — as long as you check it.
Looking after and replacing your sunglasses
Sunglasses don't last forever (and not only because we lose them). The FOPH notes that UV protection deteriorates over time. The standard's ageing test is designed to ensure safe use for two years, at a maximum of two hours a day. Scratched lenses also protect less, and the office advises throwing away worn-out or scratched pairs.
My habits for making a pair last:
- A hard case in my bag, never loose glasses rattling around with my keys.
- A rinse under clean water before wiping, so I don't grind sand into the lens.
- A microfibre cloth rather than the hem of my T-shirt.
- Glasses on my nose or in their case — not pushed up as a headband, where the arms end up splaying.
A start-of-summer ritual for this weekend? Get out every pair of sunglasses you own. Flip the arms over. Set aside the ones with no mark and no category — they're off to the next fancy-dress party, like my pink discs. For June's first pub garden, take the pair with a number printed inside. The one that looks like you.
Frequently asked questions
Are cheap high-street sunglasses as safe as designer ones?
They can be, if they carry the CE or UKCA mark and a suitable category. The FOPH test of 57 CE-marked pairs found they all met the 100% UV requirement, with no difference in optical quality between the most expensive and the cheapest. What matters is the marking — not the price tag.
How can I tell if my sunglasses block UV?
Look inside the arms and at the label or leaflet: CE or UKCA mark, filter category, "UV400" or "100% UV". None of those? No guarantee. The tint proves nothing: the College of Optometrists calls the idea that darker lenses protect more a common misconception.
Can I drive in category 4 sunglasses?
No. Category 4 lenses carry a crossed-out car symbol, and the FOPH explains they're too dark to recognise traffic lights. The Highway Code also tells drivers not to use tinted glasses at night or in poor visibility if they restrict vision. Behind the wheel, stick to category 2 or 3 — and no sunglasses after dark.
Do polarised lenses protect better against UV?
No — they're two different things. Polarisation cuts reflections from flat surfaces like water or a wet road: it's about comfort. UV protection depends on the lens material and shows up in the marking. A polarised pair still needs CE or UKCA, a category and UV400.
Which sunglasses suit a round face?
Shapes that add angles and a clean horizontal line: rectangular, trapeze, a slightly upswept cat-eye. Small round frames tend to make the face look even rounder.
Do I need sunglasses on a cloudy day?
Yes, especially near reflective surfaces. The FOPH recommends wearing them on cloudy days or under a parasol too, particularly around snow, sand, water, glass or metal. A grey British sky doesn't switch off UV.
How often should I replace my sunglasses?
The FOPH says the standard's ageing test is designed for two years of safe use (two hours a day at most) and that UV protection deteriorates over time. A scratched or very old pair should be replaced.
Sources
- NHS — Sunscreen and sun safety
- The College of Optometrists (Look After Your Eyes) — Sunglasses
- Moorfields Eye Hospital — Looking after your eyes in the sun
- GOV.UK — The Highway Code: rules for drivers and motorcyclists (89 to 102)
- GOV.UK — Regulation 2016/425 and the Personal Protective Equipment (Enforcement) Regulations 2018: Great Britain (updated March 2025)
- Swiss Federal Office of Public Health — Factsheet: sunglasses for general use (2024)