Sunglasses are divided into different categories, according to the brightness they are designed to protect against. Some sunglasses have such a strong filter that they should not be worn while driving. Here's a summary to help you choose the right sunglasses.
Design and fit may be important when you’re choosing sunglasses, but the most important thing is for the sunglasses to protect your eyes against harmful rays. This means that the sunglasses must have a sun filter. The strength of the filter depends on the brightness of sun they are designed to protect against, and this determines which category the sunglasses fall into:
Category 0 is for cloudy skies.
Category 1 is for partly cloudy skies.
Category 2 is for normal sunlight.
Category 3 is for strong sunlight.
Category 4 is for high mountains and sea. Sunglasses with Category 4 protection are not suitable for driving.