UV400 sunglasses: how to buy a pair, which lens color to choose, and the only spec that matters
Dark lenses without UV protection are worse than none. What UV400 sunglasses mean, which lens color suits what, and why polarization is separate.
The short answer
When buying sunglasses, check one thing: a UV400 or “100% UVA and UVB” marking. UV400 means the lens blocks wavelengths up to 400 nanometres, which covers all the UV reaching your eyes, and UV exposure over a lifetime is associated with cataract and pterygium. Price does not tell you this, and a cheap marked pair protects fully. A dark lens without UV protection is worse than none, because your pupil widens behind the tint and lets more UV in than squinting in bright light would. Polarization is a separate feature: it filters glare from water, wet roads and snow and is excellent for driving, but it says nothing about UV. Extra money buys optical clarity and frame build, such as better hinges and nose pads, not protection. Category 3 lenses suit bright sun, and category 4 is not legal for driving in many places. Keep a cheap marked pair in the car and spend on the pair you wear most.
Sunglasses are the one piece of eyewear where the health claim is real, and also the one where the price tells you least about whether you are getting it. A £12 pair can protect your eyes completely. A £300 pair can protect them no better, and in one specific scenario a cheap dark pair does active harm.
What should you check before buying sunglasses?
UV protection, stated as UV400 or as “100% UVA and UVB.” UV400 means the lens blocks wavelengths up to 400 nanometres, which covers the entire UVA and UVB range reaching your eyes. This is not marketing language; it is a measurable property of the lens coating or material.
It matters because ultraviolet exposure accumulates across a lifetime and is associated with cataract and with pterygium — tissue growth across the surface of the eye. Unlike most optical claims, this one has a straightforward dose-response story behind it.
Why a dark lens without it is worse than nothing
This is the part worth understanding properly, because the intuition runs backwards. Your pupil opens in response to visible dimness. Put a dark tinted lens in front of your eye and the pupil widens, because the eye reads the scene as darker. If that lens is not blocking ultraviolet, you have now created a larger opening for UV to pass through than you had with bare eyes in bright light, where the pupil would have constricted.
So the tint is not the protection. The tint without the protection is a liability. Squinting in unshaded sunlight is safer than an unmarked dark lens.
Are polarized sunglasses better for your eyes?
Constantly conflated with UV protection, and unrelated to it. A polarised lens filters light waves oscillating in one plane, which is what glare off water, wet roads, snow and car bonnets is. It cuts that glare dramatically and it is genuinely excellent for driving, on water and in snow. It has nothing to do with ultraviolet. A polarised lens may or may not be UV400; you still have to check. And there are situations where polarisation is a nuisance rather than a benefit — it can make LCD screens, including some car dashboards and phone displays, go dark or patchy at certain angles.
Are expensive sunglasses better than cheap ones?
Not protection, past the very cheapest end. What it does buy, in rough order of how much you will notice:
Optical clarity of the lens. Cheap lenses can have slight distortion that you stop noticing consciously but which causes low-level eye fatigue over a long day. This is real and it is the best argument for spending more.
Frame fit and materials. Hinges that survive, acetate that holds its shape, nose pads that do not slide. This is where the durability difference sits, and it is the same argument as everywhere else on this site: the construction is the product.
Lens category for actual conditions. Lenses are graded 0 to 4 for how much visible light they block. Category 3 is the normal bright-sunlight choice; category 4 is very dark and is not road legal for driving in many places. Worth checking if you are buying for mountains or water.
What price does not buy is UV protection, which the cheap marked pair already has.
| Feature | Does price change it? | What to know |
|---|---|---|
| UV protection | No | A UV400 or 100% UVA/UVB marking is what protects your eyes |
| Optical clarity | Yes | Cheap lenses can distort slightly and tire your eyes over a long day |
| Frame fit and materials | Yes | Hinges, acetate and nose pads are where durability sits |
| Lens category (0–4) | No | Category 3 is for bright sun; category 4 is not road legal for driving in many places |
Keep a cheap marked pair in the car and spend on the pair you wear most.
The practical conclusion
Buy a marked, inexpensive pair to keep in the car and a bag, so there is always one within reach. Spend properly on the pair you actually wear, and spend it on lens quality and frame construction rather than on the logo. Check the marking on both. And treat an unmarked pair from a market stall as an ornament rather than eyewear — it is the one category where the cheap version is not a smaller version of the expensive one, it is a different and worse thing.
If you wear prescription glasses, the same logic applies as in the blue light question: spend on the filter that has evidence behind it, and not on the one that does not.
What do sunglass lens colors do?
First, tint has nothing to do with UV protection: a pale lens can block 100% of UV and a very dark one can block none. What tint changes is contrast, depth perception and how colors read.
| Tint | Best for | Color accuracy | Avoid for |
|---|---|---|---|
| Gray | General wear, bright sun, driving | True | Flat overcast days |
| Brown or amber | Variable light, depth, poor weather | Warm shift | Tasks needing true color |
| Green | All-round use, glare | Near true | Nothing in particular |
| Rose or red | Long wear, sport, contrast | Poor | Driving |
| Yellow | Fog, dusk, low light | Poor | Bright sunshine |
Every row assumes the lens already meets UV400; tint and UV blocking are unrelated.
For one pair for general use, choose gray or green, polarized, and marked UV400. For driving in mixed weather, brown or amber. Mirror coatings help at altitude and on water, gradient lenses suit driving, and photochromic lenses react little inside a car because windscreens block UV. Polarization is a separate filter that cuts glare off water and wet roads; it can make some LCD screens hard to read.
Sources: American Academy of Ophthalmology: how to choose sunglasses
Read next: Glasses for Face Shape: Round, Square, Oval, Heart · Polarized Sunglasses: What They Do, Are They Worth It
Questions people ask about this
What does UV400 mean on sunglasses?
That the lens blocks light up to 400 nanometres, which covers the whole UVA and UVB range reaching the eye. It is equivalent to "100% UVA and UVB" and it is the one specification worth checking, because cumulative UV exposure is associated with cataract and pterygium.
Are dark lenses without UV protection dangerous?
Yes, genuinely worse than no sunglasses. Your pupil widens in response to a dark lens because the scene reads as dimmer, so an unprotected tint creates a larger opening for ultraviolet than bare eyes in bright light would. The tint is not the protection.
Is polarisation the same as UV protection?
No, and they are constantly confused. Polarisation filters light oscillating in one plane, which is what glare off water, snow and wet roads is — excellent for driving and on water, and unrelated to ultraviolet. A polarised lens may or may not be UV400, so check separately.
Do expensive sunglasses protect your eyes better?
No. Past the very cheapest end, price buys optical clarity, frame durability and fit, not UV protection — an inexpensive marked pair already blocks UV completely. Lens distortion in cheap lenses is real and causes low-level eye fatigue, which is the best argument for spending more.
What do sunglass lens categories mean?
They grade how much visible light a lens blocks, from 0 to 4. Category 3 is the usual choice for bright sunlight. Category 4 is very dark and is not road legal for driving in many places, so it is worth checking if you are buying for mountains, snow or water.
Does a darker lens mean more UV protection?
No. Tint and UV protection are unrelated: a pale lens can block 100% of UV and a very dark one can block none. Protection comes from a coating, marked as UV400.
What sunglasses lens color is best for driving?
Gray for bright, clear conditions, because it keeps traffic and brake lights true in color. Brown or amber for poor weather and variable light, since they add contrast and make depth easier to judge. Avoid rose and yellow for driving.
Are polarized lenses the same as tinted lenses?
No. Polarization is a filter that cuts glare reflected off flat surfaces such as water and wet roads, and it can be added to any tint. It can make some LCD screens and dashboards hard to read.
