The study of six families with dominant optic atrophy (DOA) originating from the neighbourhood of Leiden revealed that four could be connected through a common ancestor. A detailed analysis of 89 patients permitted a subdivision of the three remaining families into two groups: one with on the average a low visual acuity (less than 0.1) and the other with a moderately reduced visual acuity (+/- 0.35). Furthermore, differences in colour vision were observed. Genetic heterogeneity is thought to be at the root of these differences.