September 3, 2026. The tag says polarized. The lake goes quiet. You leave them on.

That is glare control, not a UV filter. Polarization is a film that blocks light bouncing sideways off water, road, and snow. Ultraviolet is a different band. The American Academy of Ophthalmology is blunt: polarization itself does not provide UV protection. Some polarized lenses add a UV finish. The polarization layer is not that finish. Read the other sticker.

Two jobs, two labels

WHO’s bar for a pair that actually covers the eye:

• UV-A and UV-B absorbed out to 400 nanometers — look for UV400, or 100% UV / UV absorption up to 400 nm
• Wraparound frames, not a small oval with open temples
• 99–100% UVA and UVB in the WHO and EPA wording

Cancer Council’s UV400 note is a little more specific: a UV400 claim should block at least 95% of UV between 190 and 400 nm. Separately, SunSmart says Australian category 2, 3, and 4 lenses absorb more than 95% of UV. Treat “polarized” as extra comfort, not either of those claims.

The two features run independently. A UV400 pair does not have to be polarized. A polarized pair does not have to be UV400. AAO says the same thing in reverse: blocking UV does not make a lens polarized. You can want both. You cannot substitute one for the other.

In Australia and New Zealand, the sunglass standard splits lenses into categories. The number is mainly how dark they are for glare, not a separate UV grade. 0 and 1 are fashion spectacles, not sunglasses—limited or no UV on 0, only some on 1. 2, 3, and 4 are sunglasses with a good UV spec; 4 is a very dark special-purpose tint and is not for driving. Elsewhere, skip the category number and find the UV400 / 100% line.

Price does not vote. WHO: you cannot tell UV blocking from color, darkness, or cost. AAO: a drugstore pair labeled 100% UV-blocking beats a designer pair with no protection.

Darkness is not the filter

Dark glass makes you comfortable. You squint less. Glare drops. UV does not care about that comfort.

AAO: darker is not better. Mirror coatings and tint color—amber, gray, rose—are style and contrast, not a UV rating. Lenses that darken in the sun add glare relief. SunSmart notes they do not necessarily filter more UV.

The cue you feel is not the dose. Polarized water looks safer. The index on the homepage has not moved.

Open sides still feed the eye

A rated lens only covers the disc in front of you. UV also arrives from the side, from sky scatter, and bounced up from the ground.

Cancer Council: non-wraparound sunglasses are not effective against peripheral UV. Their sun-protection guidance puts about 40% of the UV that reaches the eye on that peripheral path. A brimmed hat cuts UV to the eyes by about 50%. Hat plus sunglasses that meet the standard: up to about 98%. That is why a baseball cap still wants real lenses, not just a visor.

Snow, water, and pale sand throw UV up under the frame—the same bounce as in shade does not cancel UV. Ski and marina days are not a tint problem only. They are a wrap-and-bounce problem.

UV-blocking contact lenses can cut about 90% of UVA through the lens. They do not cover the white of the eye or the skin around it. Sunglasses still do that job.

Before you put them on

Use the live UV index first, then read the frame:

1. Check today’s peak. WHO and Cancer Council treat 3 (Moderate) as the line to protect skin and eyes. If the peak is 3 or above, sunglasses are part of the plan—not a glare accessory for High days only.
2. Find the UV line, then polarization. UV400 or 100% UVA/UVB. Polarized is optional for water, road, and snow glare. AAO: polarized lenses can wash out LCD dashboards and phones, and can hide ice on a road or ski run. Drop them for those jobs; do not drop the UV pair.
3. Close the sides. Wraparound or large lenses that sit close. Open temples leak the peripheral path.
4. Add a real brim when the peak is High or the ground is bright. The visor is not a substitute—see the hat numbers above.
5. Do not stare at the sun. No everyday pair is an eclipse filter or a welding shade. AAO also flags tanning beds and extreme snowfields as cases where ordinary sunglasses are not enough—use goggles or purpose-built filters there.

If the only pair that stays on is a cheap wrap with a UV400 tag, that beats an expensive polarized oval with no UV line.

Limits

UV400, 400 nm, and the 99–100% UVA/UVB figures summarize WHO, EPA, and AAO public guidance on sunglasses. The 95% / 190–400 nm UV400 note, lens categories 0–4, the 40% peripheral path, the 50% hat cut, and the 98% hat-plus-glasses figure summarize Cancer Council Australia and SunSmart public guidance. Polarization-as-glare, not UV, is AAO. Exact dose at the eye moves with sun angle, frame gap, and what the ground is doing.

UV readings on UV Index Today are estimates for everyday sun-safety planning, not medical advice. For SPF timing and related Q&A, see the Guide. For your location’s current numbers, open the homepage.