L-Dopa improves colour vision in Parkinson's disease.

In recent studies disorders of colour vision in Parkinsonian patients have been demonstrated. Up to now, the influence of dopaminergic treatment on those phenomena remains unclear. We therefore performed a colour vision test (Farnsworth-Munsell 100 Hue Test) in 19 patients with Parkinson's disease before and after the oral application of the morning dose of L-Dopa. The colour discrimination was significantly improved after the ingestion of L-Dopa. There was no different effect of L-Dopa on the blue-yellow or red-green axis of colour vision. The morphological structures responsible for these colour vision disturbances are unknown, but it can be concluded that the dopamine deficiency in Parkinson's disease is not restricted to the basal ganglia but may involve the visual system as well.