Effect of a dopaminergic agonist, piribedil (Trivastal 50 mg LP), on visual and spatial integration in elderly subjects.

Dopamine acts as a neuromodulator in the retina. Dopaminergic deficiency of any origin, as observed in elderly subjects, is associated with altered visual performances, and more specifically with altered perception of contrasts. The goal of this study was to compare contrast vision in elderly subjects and young subjects (first phase, n = 20), then to compare this function in elderly subjects before and after 3 months of treatment with a dopaminergic agonist, piribedil (Trivastal 50 mg LP), administered once daily (second phase, n = 20). The perception of contrast was analysed using a test measuring sensitivity to colour contrast yielding threshold values for sensitivity to contrast in eight spatial frequencies and three colours (red, green, blue) and in two directions (horizontal and vertical). The results of the first phase of the study demonstrated that elderly subjects showed a decrease in contrast perception in comparison with young subjects, primarily in the high frequency range, and over the full range of stimulation for direction and colour. In the second phase, elderly subjects, in comparison with young subjects, showed altered visual contrast, again in the high frequency range, but also in the low frequency range for horizontal simulation with red and blue. After 3 months of treatment with piribedil the mean contrast sensitivity threshold, over the entire frequency range, had significantly increased (P less than 0.05) for all stimulations, apart for red in the vertical direction. These results underline the value of treatment with a dopaminergic agonist, piribedil in visual disturbances in patients with dopaminergic deficiency (Parkinson patients or elderly subjects).