Visual system abnormalities in patients with Parkinson's disease.

Visual evoked potentials (VEPs) and contrast sensitivity measurements were determined in normally sighted patients with Parkinson's disease (PD). Prolonged latencies of the first major positive (P100) wave of the VEP elicited by an alternating vertical grating were noted. The delay in latency was positively correlated with the severity of the movement disability. Subjective testing of contrast thresholds demonstrated significant elevation of thresholds in PD. Electroretinographic oscillatory potentials were elicited to determine if the delay in P100 latency was of retinal origin. No specific lesion could be identified to account for the abnormality in VEP or in contrast testing results.