UV400 Protection Explained: What It Means and Why It Matters

July 18, 2026

What Is UV400 Protection and Why Does It Matter?

UV400 is the highest standard of ultraviolet protection in sunglasses. A UV400 rating means the lenses block all light wavelengths up to 400 nanometres — covering 99-100% of both UVA and UVB rays. This is the standard recommended by ophthalmologists worldwide.

UVA vs UVB: What's the Difference?

UVB rays (280-315 nm) cause surface-level damage: sunburn and photokeratitis. UVA rays (315-400 nm) penetrate deeper, causing cataracts, macular degeneration, and premature ageing around the eyes. Both are present year-round — up to 80% of UV radiation penetrates cloud cover.

UV400 vs UV380 vs "100% UV Protection"

UV380 misses a portion of UVA radiation between 380-400 nm. Vague claims like "100% UV protection" without specifying the wavelength may not meet UV400. Look specifically for "UV400" — it's the clearest, most protective standard.

Lens Categories Explained

European sunglasses use a 0-4 scale. Category 3 lenses transmit 8-18% of visible light — standard for daily outdoor use and driving. Category 4 is for extreme conditions only (not legal for driving). All Frame Studio sunglasses are Category 3 UV400.

Does Lens Colour Affect UV Protection?

No. UV protection comes from a chemical lens coating, not tint darkness. A dark lens without UV coating is worse than no sunglasses — it dilates your pupils, letting more UV in.

Polarisation vs UV Protection

These are separate features. Polarisation reduces glare from reflective surfaces. UV400 blocks UV radiation. If choosing one, UV protection is non-negotiable.