The purpose of this study is to test the hypothesis that colour vision impairment is associated with amyotrophic lateral sclerosis (ALS). Abnormalities of the inner and intermediate retinal structures in patients with ALS have been described using optical coherence tomography (OCT) and histopathology, with colour vision as a potential marker of these changes. Monocular colour vision was assessed using the L’Anthony D15 colour test, in subjects with definite or probable ALS as well as in control subjects. Results reported by the authors show ALS subjects to have impaired colour vision in 16 out of 25 cases (64%). Diffuse colour discrimination defects are detected in ALS subjects at younger ages than in control subjects. The authors conclude that further study is needed to confirm the findings in a larger cohort and to explore the association between colour discrimination abnormalities and structural markers of retinal involvement and ALS disease severity.