Visual electrophysiology in Parkinson's disease: PERG, VEP and visual P300

A retinal dopaminergic deficiency underlies some visual changes in Parkinson's disease (PD), in particular those elicited by stimuli near the peak of the human and monkey spatial contrast sensitivity. The correspondence of retinal changes and VEP alterations is not perfect: they do not seem to rely on identical mechanisms. It seems that additional pathology beyond the retina affects visual responses, including VEPs. The relevance of "distal" primary VEP changes to higher cognitive visual abnormalities in PD is not established at present.