Mesopic visual acuity requirements for driving licenses in the European Union-Research Report.

In this study different methods for determining the mesopic visual acuity in candidates for driving licenses group 2 are presented (Royal Decree, 1998, European norms). Results of normal subjects are compared. Depending on the method used, visual acuity obtained under mesopic conditions, with an illuminance of 1 lux, showed a mean ranging from 0.5 to 0.65, which is clearly above the legal norm of 0.2. A comparative study of the three published official norms demonstrates that the stringent norms of 1966 do not match those of 1988 and 1998, resulting in a wider margin of acceptability, to the advantage of the candidate.