Various methods have been developed in different countries for assessing the risk of direct glare from a lighting system, e.g. Visual Comfort Probability, the Glare Index and the Luminance Limiting Curve System.

In an attempt to achieve international harmonisation of the various glare classification systems, the CIE (Commission International de l'Eclairage) has developed the UGR method (Unified Glare Rating), which is to be introduced as part of the process of harmonisation for European standards (CEN).

The DIN standard is currently based on the Söllner limiting curve method.