what is UV400 lens

Uv400 Means 100% Uv Resistance. Ultraviolet Light Refers To The Solar Light With A Wavelength Between 200nm And 380nm, Including Three Types: Uva With A Wavelength Of 315nm ~ 380nm, Uvb With A Wavelength Of 280nm ~ 315nm And Uvc With A Wavelength Of 200nm ~ 280nm. Among The Sunlight Reaching The Earth's Surface (290nm ~ 2000nm), Ultraviolet Light Accounts For About 13%, Of Which Uva Accounts For 97%, Uvb Accounts For 3%, And Uvc Is Close To 0. The Damage Of Ultraviolet Rays To Human Eyes Mainly Depends On The Wavelength, Radiation Time And Intensity Of Ultraviolet Rays And The Strength Of Human Eye Self-defense Mechanism. Cornea And Lens Are The Eye Tissues Most Often Damaged By Ultraviolet Rays. Solar Keratitis, Corneal Endothelial Injury And Solar Leukopenia Are The Most Relevant Eye Diseases. Therefore, When Buying Sunglasses, We Should Choose Uv400 Sunglasses, Because This Kind Of Lens Can Resist Uva, B And C Wavelengths; The General Sunglasses Can Only Reduce The Luminosity And Can Not Block Ultraviolet Rays. If A Pair Of Sunglasses Can Only Block Strong Light But Not The Same Amount Of Ultraviolet Light, The Wearer Will Accept More Ultraviolet Light Than Not Wearing Sunglasses (wearing Sunglasses Will Reduce The Flux Into People's Eyes, Resulting In The Increase Of The Wearer's Pupils, But More Ultraviolet Light), Which Further Deepens The Damage To The Eyes. As For Polarized Sunglasses, The Harm Of Ultraviolet Rays To Human Body Is "cumulative", That Is To Say, The Longer You Are Exposed To The Sun, The Greater The Harm Of Ultraviolet Rays.