New sunglasses look great, but their real job is to block the sun's ultraviolet (UV) rays. Not every pair does, whatever the price, age or style. Here is how to read the label, test a pair you're unsure of and know when it's time to replace them.
What UV does to your eyes
- UVA (315–400 nm): about 95% of the UV that reaches the ground. It penetrates deep into the eye and is linked to cataracts and macular degeneration over a lifetime.
- UVB (280–315 nm): higher energy, mostly absorbed by the front of the eye. It causes photokeratitis (a sunburn of the cornea, also called snow blindness) and pterygium.
- UVC (100–280 nm): blocked by the atmosphere, so it isn't a concern outdoors.
Read the label: UV400 and 100% UV protection
"UV400" means the lens blocks light with wavelengths up to 400 nanometres, which covers all UVA and UVB. "100% UV protection" or "100% UVA/UVB" means the same thing. Vague wording like "UV absorbing" or "blocks UV" doesn't tell you how much is blocked.
In the US, sunglasses must pass the FDA's impact test for lenses (21 CFR 801.410). UV performance is covered by the voluntary ANSI Z80.3 standard, so look for UV400 or 100% UVA/UVB on the label or product page. Every OLIVIO&CO pair offers 100% UV protection.
Darker doesn't mean safer
Tint only reduces visible light. It does nothing for UV on its own. In fact, dark lenses without UV filtering can be worse than no sunglasses: the dark tint makes the pupils widen, which lets more UV into the eye. UV protection comes from the lens material or a UV-blocking layer, and it can be built into a light tint just as well as a dark one.
Polarized is not the same as UV protection
Polarized lenses cut glare reflected from water, roads and snow. They don't automatically block UV. The best sunglasses are both polarized and UV400.
Not sure about a pair? Test it
Vintage sunglasses, novelty pairs and unlabelled kids' sunglasses may not block UV at all. Many optical shops can check them with a UV meter in under a minute, often for free.
Choose for coverage
- Larger lenses and close-fitting or wraparound frames let less UV in around the edges.
- Near water, sand and snow, reflected UV adds to the direct sun, so coverage matters even more.
- The same rules apply to children, whose eyes let more UV through to the retina than adult eyes do.
Wear them in all weather
UV passes through clouds, and fresh snow reflects up to about 80% of it. Wear sunglasses whenever you're outside for long, not only on bright summer days.
When to replace your sunglasses
A study from the University of São Paulo found that heavy sun exposure can gradually wear down the UV protection of some lenses, and suggested replacing sunglasses after about two years of daily use. Scratches also matter: on lenses where UV protection is a surface coating, scratches can let more UV through. Replace any pair that is badly scratched, no longer fits, or that a child has outgrown.
