Retinal dysfunction in Parkinson's disease-results of the extended protocol for photopic negative response (PHNR) full-field electroretinogram (ERG).

This study demonstrated reduced a-wave, b-wave and PhNR-wave amplitudes on ERG measurements in PD patients. These findings suggest that the whole ERG response, not just the PhNR, is attenuated in patient with PD, suggesting a possible involvement of the visual system in the disease.