Colour vision abnormalities and movement time in Parkinson's disease

Visual system dysfunction has been reported in Parkinson's disease (PD). The objective of the present study was to evaluate a putative association of distorted colour vision and delayed initiation and execution of movement in PD. We performed the Farnsworth-Munsell 100-hue test and estimated the total error score in 30 previously untreated parkinsonian patients and 30 age- and sex-matched controls. We then determined slowness in motor readiness and motor programming in the parkinsonian subjects on the same day. Subjects were asked to press a start button and release it after the randomized appearance of a visual stimulus and to move their right index finger to a reaction button as quickly as possible. Reaction time was considered as elapsed time between onset of the stimulus light and release of the start button, movement time was the time period between release of the start button and the pressing of the reaction button. Significant differences appeared between parkinsonian patients' and controls' reaction times (P = 0.007), movement time (P = 0.001) and total error score (P = 2.23E-08). A significant relation (Spearman R = 0.473, P = 0.008) was found between movement time and total error score, but not between reaction time and total error score (Spearman R = 0.259, P = 0.166). We conclude, that visual dysfunction and execution of movement are more influenced by altered dopaminergic neurotransmission in PD in comparison to the initiation of movement.