What does UV 400 mean?
The UV 400 sun protection means that the sunglasses block all UV rays in the range of 100 to 400 nanometers and thus block all UV-A, UV-B and UV-C rays that are dangerous to the eye.
Why sun protection?
Even if it may not be noticed immediately, unfiltered sunlight is very irritating to the eye. The short-wave ultraviolet radiation (UV radiation) is invisible to the eye, but it can promote diseases such as inflammation of the eye or cataracts. If the exposure to the sun is too high in the long term, you can do without sunglasses with UV 400 protection possibly permanently even go blind.
In addition to blocking the dangerous UV rays, sunglasses with UV 400 protection also have the advantage that there are no glare effects and visibility is better overall in the sun.