Sunglasses do two jobs: they cut glare so you can see comfortably, and they protect your eyes from ultraviolet light. The second job is the important one, and it has nothing to do with how dark the lenses look. A pale lens can block UV completely, and a very dark one can block very little.
When you compare designer sunglasses, check three things before style: a statement of full UV protection (often written as UV400), a CE or UKCA mark showing the glasses meet the sunglasses standard, and the filter category, which tells you how dark the lens is and whether you can drive in it.
UV protection and safety marks
UV400 means the lenses block ultraviolet light up to a wavelength of 400 nanometres, which covers both UVA and UVB. Sunglasses sold in the UK should carry a CE or UKCA mark, which shows the maker says they meet the relevant standard, BS EN ISO 12312-1. The mark and the filter category are often printed on the inside of an arm.
Be wary of sunglasses with no markings at all. Dark lenses without UV filtering can do more harm than none, because your pupils open wider behind them and let more UV in.
Filter categories 0 to 4
The filter category describes how much visible light the lens lets through.
| Category | Tint | Light let through | Typical use |
|---|---|---|---|
| 0 | Clear or very light | Over 80% | Fashion, cloudy days |
| 1 | Light | 43 to 80% | Dull days |
| 2 | Medium | 18 to 43% | Everyday UK summer |
| 3 | Dark | 8 to 18% | Bright sun, beach, holidays |
| 4 | Very dark | 3 to 8% | Glaciers, high mountains |
Category 4 lenses are not suitable for driving at all. The College of Optometrists also notes that lenses letting through less than 75% of light, which includes categories 2 and 3 and some category 1 lenses, are not suitable for driving at dusk or at night.
For most people in the UK, a category 2 or 3 lens is the practical choice.
Polarised, gradient and mirrored lenses
- Polarised lenses cut reflected glare from water, wet roads and snow, which many drivers and anglers like. They can make some phone, car and cash machine screens look dark or patchy at certain angles. Polarisation is about glare, not UV; check UV protection separately.
- Gradient lenses are darker at the top and lighter at the bottom, useful for driving and reading a dashboard. They are a popular fashion choice.
- Mirrored lenses reflect more light away. The colour of the mirror is mostly about style.
- Photochromic lenses darken in UV light. They may not darken fully behind a car windscreen, which blocks much of the UV that triggers them.
Frame size and shape
Frames often have three numbers printed on the arm, for example 55 18 140. These are the lens width, the bridge width and the arm (temple) length, in millimetres. If you own a pair that fits well, compare those numbers.
A good fit means:
- The frame sits level and does not slide down your nose when you look down.
- Your eyelashes do not touch the lenses.
- The arms do not press on your temples or behind your ears.
- Larger and wraparound frames block more light coming in from the sides.
Shape is a matter of taste. Common advice is to choose a frame shape that contrasts with your face, such as rounder frames for angular faces and squarer frames for round faces, but plenty of people ignore it happily.
Some listings in the sunglasses range are optical frames rather than sunglasses. These come with demonstration lenses and need prescription lenses fitted by an optician. Check the product name before you order.
Prescription and children’s eyes
If you wear glasses, prescription sunglasses or clip-on lenses from an optician are safer than wearing non prescription sunglasses over contact lenses you do not normally use. Children’s eyes let more UV through to the back of the eye than adults’ do, so choose UV400 sunglasses for them too, and a hat with a brim. If you have any eye condition, ask your optician which lenses suit you.
Care
- Keep sunglasses in a hard case when not on your face, rather than loose in a bag or pocket.
- Clean lenses with a microfibre cloth and lens spray or mild soapy water, never with clothing or kitchen roll.
- Do not leave them on a car dashboard in the sun; heat can warp frames and damage coatings.
For a matching bag, watch or belt, browse the wider accessories section or the bags range, and see the guide to choosing a handbag.
Quick checklist
- Look for UV400 or 100% UV protection.
- Check for a CE or UKCA mark.
- Choose filter category 2 or 3 for most UK use.
- Never drive in category 4 lenses, or in tinted lenses at night.
- Consider polarised lenses for glare from water and roads.
- Compare lens, bridge and arm sizes with a pair that fits.
- Check whether a listing is sunglasses or optical frames.
Common questions
Are darker lenses better for my eyes?
Not necessarily. Darkness affects comfort, not UV protection. A lens needs a UV filter to protect your eyes, whatever its tint.
Can I drive in polarised sunglasses?
Yes, as long as the filter category is 0 to 3 and you are driving in daylight. Some drivers find polarised lenses make certain dashboard screens hard to read, so try them before a long journey.
Do expensive designer sunglasses protect better?
Price and brand mostly reflect frame design and materials. A properly marked pair with UV400 lenses protects your eyes whatever it costs.
