The retinal nerve fiber layer mean thickness in patients with early Parkinson's disease reflects striatal dopamine...

The purpose of this study was to investigate the relationship between the retinal nerve fiber layer (RNFL) mean thickness and striatal dopamine (DOPA) uptake in patients with early Parkinson's disease (PD) and to evaluate the potential value of the RNFL mean thickness in the diagnosis of early PD.

Plasma levels of α-synuclein (α-syn) were measured by enzyme-linked immunosorbent assay (ELISA). Motor and nonmotor symptoms were assessed with related scales. DOPA uptake was measured with DOPA positron emission tomography (PET)/ computed tomography (CT). The RNFL mean thickness was measured with swept source optical coherence tomography (SS-OCT).

There was a negative correlation between plasma α-syn levels and the SORs of the contralateral caudate nucleus, anterior putamen and posterior putamen in PD patients; similar results were observed on the ipsilateral side. A positive correlation between the RNFL mean thickness and the SORs of the contralateral caudate nucleus, anterior putamen and posterior putamen was observed in PD patients; similar results were seen on the ipsilateral side. Receiver operating characteristic (ROC) curve analysis confirmed the value of the RNFL mean thickness in the diagnosis of early PD.

The strength and significance of our study are that it is the first to indicate, on the basis of the α-syn mechanism, that the mean RNFL thickness partly reflects striatal dopamine uptake in the brain, suggesting that the mean RNFL thickness may have a certain value for the early diagnosis of PD.