Not all sunglasses block the same amount of UV rays. Since the color of the glass has nothing to do with the amount of UV rays it blocks, it is difficult to say how much protection a particular color of glass provides. That is why in many cases a sticker is stuck to the glass, stating the amount of UV rays that are filtered.
Regularization around sunglasses
Several regulatory organizations have established standards for protection against UV light. In the United States this is the ANSI standard, in Europe the CEN.
ANSI includes 3 standards for both cosmetic quality, refractive properties (e.g. distortion) and resistance to impact. Sunglass lenses are thus divided into three groups:
- Cosmetic : blocks at least 70% of UV-B and 60% of UV-A
- General use : blocks at least 95% UV-B and minimum 60% UV-A
- Special use : block at least 95% UV6B and 60% UV-A.
If sunglasses in the United States do not meet one of these three groups, the company is obliged to provide the glass with a sticker ‘not suitable for driving’.
According to CEN standards, sunglasses are divided into four groups, depending on their properties to filter UV rays: weak, medium, strong and intense. Glasses belonging to the latter group are not suitable for use while driving.