Polarised vs UV400 Sunglasses,What's the Actual Difference?

Walk into any sunglass shop and you will hear "polarised" used as if it means protected. Patients regularly tell us they wear polarised sunglasses and assume this means their eyes are protected from UV damage. It doesn't,and the confusion has real consequences for long-term eye health.

What Polarisation Actually Does

Polarised lenses contain a chemical filter oriented in a single direction (typically horizontal) that blocks horizontally polarised light. When light reflects off a flat horizontal surface,water, wet road, a car bonnet,it becomes horizontally polarised. A polarised lens blocks this reflected glare, dramatically improving visual comfort and contrast in these conditions.

Polarisation does nothing to block UV radiation. A lens can be polarised and completely transparent to UV. A lens can be UV400 (blocking all UV below 400nm) and not polarised at all. They are independent properties.

What UV400 Actually Means

UV400 means the lens blocks all ultraviolet light with a wavelength up to 400nm,which covers both UVA and UVB entirely. This is the minimum standard for genuine UV eye protection. In Australia, sunglasses sold as providing UV protection should comply with AS/NZS 1067, which sets testing requirements for UV transmittance.

You Need Both,For Different Reasons

• UV400: Protects the eye from cumulative UV damage,cataracts, macular degeneration, pterygium, eye cancer. This is a health requirement, not a comfort preference.
• Polarisation: Reduces glare in specific conditions,driving on wet roads, fishing, water sports, outdoor work. This is a visual comfort and performance feature.

Ideal sunglasses for most Australians provide both. The good news: most quality sunglasses sold in Australia include UV400 coating as standard, and premium versions add polarisation. Cheap, unbranded sunglasses,particularly those without AS/NZS 1067 marking,may not provide either.

The Dark Tint Problem

A very dark lens without UV coating may actually be worse than no sunglasses at all. The dark tint causes the pupil to dilate, allowing more light (including more UV) to enter the eye. If the lens doesn't filter UV, more UV reaches the retina than with no sunglasses. This is the hidden danger of cheap, dark-tinted sunglasses.