Effect of levodopa on the human pattern electroretinogram and pattern visual evoked potentials.

Pattern electroretinograms (P-ERGs) and pattern visual evoked potentials (P-VEPs) were recorded at three luminance levels and five different check sizes in a group of 16 control subjects before and after the oral administration of levodopa. At the lower luminance levels, significant decrease in P-ERG and P-VEP latencies were found. For P-VEPs the latency changes occurred only at small check sizes. No changes were observed in control experiments without levodopa administration. Our results show that levodopa-induced changes even occur at the retinal level and support a dopaminergic involvement in light and dark adaptation. Our observations are in agreement with a VEP delay found in Parkinson's disease and with a VEP latency increase in rats after dopamine depletion.