What Are Polarised Sunglasses? Glare, UV and What Matters

The short answer: polarised lenses cut reflected glare, such as the dazzle off water, wet roads and car bonnets. UV protection is a separate job, and it comes from the lens's UV filter, not from polarisation. A polarised lens isn't automatically UV-protective, and a UV-protective lens isn't automatically polarised. For bright New Zealand days, look for both, clearly labelled.

Below, we explain how each one works, what lens categories mean, and what to check when you're buying sunglasses in NZ.

What does "polarised" actually mean?

Sunlight contains light waves vibrating in many orientations. Reflections from horizontal surfaces such as water or wet roads can be strongly horizontally polarised. This bright reflected light is a common source of glare.

A polarising filter reduces much of that horizontally polarised reflected light. This can make glare less distracting and details easier to see. It is a different feature from the filter that blocks ultraviolet radiation.

Polarised vs UV protection: two different jobs

This is the part most people mix up. Polarisation and UV protection are separate features that happen to come together in many sunglasses.

The Cancer Society's SunSmart programme puts it plainly: polarised sunglasses reduce glare and make it easier to see on a sunny day, but they don't increase UV protection.

What does UV400 mean?

UV400 describes protection against ultraviolet wavelengths up to 400 nanometres, covering UVA and UVB. Check the product information and supporting test documentation; polarisation and lens colour do not prove a UV rating.

Darker or mirrored doesn't mean more UV protection

A dark tint or a mirror coating reduces how much visible light reaches your eyes. Neither one tells you how much UV the lens blocks. A very dark lens with a poor UV filter can feel protective while doing little for UV. The label is what counts, not the look.

Polarised vs non-polarised sunglasses: which should you choose?

Both can give good UV protection, as long as the label backs it up. The real difference is glare.

• Choose polarised if you spend time around water, roads, snow or anywhere bright light bounces back at you, or if glare is what makes you squint.
• Consider non-polarised if you need to read LCD screens outdoors a lot, such as instruments or displays for work, because polarised lenses can make some screens hard to read at certain angles.

For most everyday wear in New Zealand, polarised lenses with a clear UV rating are a practical all-round choice.

Lens categories: what the numbers mean

Under the Australian/New Zealand standard, lenses are grouped into five categories based on how much glare they cut:

• Category 0 and 1: fashion spectacles, not sunglasses. They offer little or no sun-glare reduction, and Category 1 is not suitable for driving at night.
• Category 2: sunglasses with a medium level of sun-glare reduction and good UV protection.
• Category 3: sunglasses with a high level of sun-glare reduction and good UV protection.
• Category 4: special-purpose sunglasses with a very high level of sun-glare reduction and good UV protection. They are not suitable for driving or road use.

Category and polarisation are separate. The category tells you how dark the lens is overall. Polarisation tells you whether it also filters reflected glare. A polarised lens still has its own category, and that category, not the polarisation, decides whether the sunglasses are suitable for driving.

Where polarised lenses make the biggest difference

• On the water. Polarised sunglasses are popular for fishing, boating, kayaking and paddleboarding because they cut surface glare and help you see into the water.
• At the beach. Less dazzle from wet sand and the sea.
• Driving on bright or wet days. Reflections from wet roads and other cars are reduced. Check your lens category first: Category 4 is never suitable for driving.
• In the snow. Snow is very reflective, so glare control helps, and so does good coverage, because snow also reflects a lot of UV.
• Everyday bright days. Walking, cycling or sitting outside a café, where windows, cars and pavement all bounce light around.

The trade-offs worth knowing

• Screens can look strange. Many LCD screens give off polarised light, so through polarised lenses some screens can look dim, patchy or completely black at certain angles. Examples include car dashboard displays, cash machines, some phones and some watches. Tilting your head usually helps. If you need to read screens outdoors for work, try the lenses first.
• They're not for low light. Polarised lenses darken the view slightly. No sunglasses, polarised or not, should be worn for driving at night or in dull light.
• You can feel glare reduction, but not UV protection. A pair that feels comfortable in bright light hasn't necessarily been tested for UV. Check the label.

How to tell if your sunglasses are polarised

• The screen test. Look at an LCD screen, such as a laptop or a car display, through one lens and slowly rotate the sunglasses about 90 degrees. If the screen darkens noticeably at one angle, the lens is polarised. Screens vary, and many phones behave differently, so try more than one if the result isn't clear.
• The two-pair test. Hold a pair you know is polarised in front of the pair you're testing, then rotate one of them 90 degrees. If the overlapping area goes very dark, both are polarised.

These tests only confirm polarisation. They tell you nothing about UV protection.

Buying sunglasses in NZ: a quick checklist

Whether you're shopping in store or buying polarised sunglasses online in NZ, these checks matter more than the brand name or the price tag:

1. UV protection on the label. Look for UV400 or 100% UV protection, and ideally AS/NZS 1067.1:2016 compliance with the lens category stated.
2. The right category for how you'll use them. Categories 2 and 3 are general-purpose sunglasses. Category 4 is for special-purpose use only and must not be used for driving.
3. Polarised if glare is what bothers you. It's especially worthwhile around water, roads and snow.
4. Good coverage. Close-fitting, wrap-around styles and larger lenses reduce the light and UV coming in around the edges.
5. Fit and comfort. Online, look for frame and lens measurements so you can compare them with a pair you already own. The best sunglasses are the ones you'll actually keep on.
6. Clear lens information. A good product page should tell you plainly whether the lenses are polarised and what UV protection they have.
7. Delivery and returns. When buying online, check shipping costs to your address, including rural delivery, and the returns policy before you order.
8. A hat as well. SunSmart notes that combining a hat with good sunglasses gives considerably more protection than either on its own.

For more on how UV affects your eyes, read our guide to sun damage and UV protection in New Zealand.

Shopping for polarised sunglasses in NZ?

Explore FRMZ’s polarised sunglasses for New Zealand with a clean, minimalist look. Every pair has polarised lenses with UV400 protection, as listed on each product page, alongside a lightweight TR90 frame and a one-piece shield lens. Each product page also lists approximate frame and lens measurements.

• Understated: the all-black Black FRMZ, with a plain, non-mirrored lens.
• A bit of colour: our mirrored polarised sunglasses pair a mirrored lens with black or coloured frames.
• Everything: browse all our polarised shield sunglasses or the full FRMZ range.

We offer free shipping across New Zealand, rural addresses included. See our shipping policy and returns and refund policy for details. Questions about our lenses? Get in touch and we'll help where we can.

Frequently asked questions

Are polarised sunglasses better for your eyes?

Polarisation makes bright, reflective conditions more comfortable to look at, but it doesn't add UV protection. For UV, what matters is the lens's UV rating and how well the sunglasses cover your eyes.

Do polarised sunglasses block UV?

Not by themselves. Many polarised lenses also include a UV filter, but the two are separate features. Check the label for UV400, 100% UV protection or a stated standard and lens category.

Can I drive in polarised sunglasses?

That depends on the lens category, not on polarisation. Category 4 sunglasses must never be used for driving, and no sunglasses should be worn for driving at night or in dull light. Polarised lenses can also make some dashboard screens harder to read at certain angles.

Are mirrored lenses polarised?

Not necessarily. A mirror coating reflects some visible light, but it doesn't make a lens polarised or UV-protective on its own. Check the label for each feature. FRMZ's mirrored colourways are polarised, with UV400 protection.

Are polarised sunglasses good for fishing?

Yes, this is one of the main reasons people choose them. Polarisation cuts glare off the water's surface, which makes it easier to see into the water. As with any sunglasses, check the UV rating as well.

Do cheap sunglasses protect against UV?

Price alone does not establish UV protection. Check the stated UV rating, lens category and any supporting test information rather than assuming that either a low or high price proves quality.

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This article is general information only and is not medical advice. If you have concerns about your eyes, talk to an optometrist or doctor.

Sources

• SunSmart NZ (Cancer Society): Wrap on sunglasses
• ACCC Product Safety: Sunglasses and fashion spectacles mandatory standard
• American Academy of Ophthalmology: What are polarized lenses for? (2024)