Ganzfeld electroretinographic findings in parkinsonism: untreated patients and the effect of levodopa intravenous infusion.

Two groups of patients with primary Parkinsonism were studied with the ganzfeld electroretinogram (ERG): seven patients who had never received dopamimetic agents, and six patients given an infusion of levodopa following a period of medication withdrawal. Patients in the first category had a subtle increase in the latency of their short-wavelength sensitive cone response recorded from the retina ipsilateral to their more symptomatic side. Most patients in the second category demonstrate an improvement in their ERG when the responses recorded following levodopa infusion were compared with baseline responses obtained during the period of medication withdrawal. These results suggest that one role of retinal dopamine may be maintenance of normal retinal responsiveness to flash stimuli.