Researchers of a small case-control study (20 people with Parkinson’s disease [PD] vs 20 age-matched controls) used full-field electroretinography (ERG) to probe retinal function across cone (photopic) and rod (scotopic) pathways and the retinal ganglion cell (RGC) output (photopic negative response [PhNR]). Investigators recorded standardized flash protocols after light and dark adaptation and quantified ERG components linked to photoreceptors (a-wave), bipolar/inner retinal activity (b-wave), oscillatory potentials (OPs; amacrine/bipolar interactions), and PhNR (RGC function). Compared with controls, PD participants showed reduced amplitudes in rod b-wave, scotopic OPs, photopic b-wave, and PhNR (b-wave and PhNR wave), consistent with impaired inner retinal signaling and attenuated RGC output.
Sex-stratified analyses suggested particularly pronounced abnormalities in women with PD—most notably impaired scotopic b-wave and PhNR, pointing to diminished amacrine cell output—raising the possibility of sex-specific retinal signatures. Because PD is typically diagnosed after years of neurodegeneration, the authors propose ERG as a noninvasive candidate biomarker for earlier detection and longitudinal monitoring. The findings align with prior reports of PD-related visual dysfunction and support further validation of ERG metrics—potentially useful in preclinical or prodromal stages and in tracking disease progression—while acknowledging the small sample size and need for replication.
Reference: Livingston R. Retinal Response Testing May Help Early Diagnosis of Parkinson’s Disease. HCP Live. Published May 2, 2025. Accessed October 24, 2025. https://www.hcplive.com/view/retinal-response-testing-may-help-early-diagnosis-of-parkinson-s-disease
