The European standard defines functional requirements for different types of personal eye protectors as well as their marking. In order to ensure the vision required for the respective operation, the prismatic, spheric and astigmatic refraction powers have to meet the requirements specified in the standards. According to those refraction powers, the lenses are divided in three optical classes:

Class 1: for the long-term use (e.g. operations with particularly high requirements on the visual performance)
Class 2: for the occasional use (e.g. operations with average requirements on the visual performance)
Class 3: only in exceptional cases (e.g. for rough work without major requirements on the visual performance)