Is there any correlation between alpha-synuclein levels in tears and retinal layer thickness in Parkinson's disease?

Purpose To determine the total alpha-synuclein (αSyn) reflex tears and its association with retinal layers thickness in Parkinson's disease (PD). Methods Fifty-two eyes of 26 PD subjects and 52 eyes of age-and sex-matched healthy controls were included. Total αSyn in reflex tears was quantified using a human total αSyn enzyme-linked immunosorbent assay (ELISA) kit. The retinal thickness was evaluated with spectral-domain optical coherence tomography. The Movement Disorder Society-Unified Parkinsońs Disease Rating Scale (MDS-UPDRS), Non-Motor Symptoms Scale (NMSS), and Montreal Cognitive Assessment (MoCA) were used to assess motor, non-motor, and cognition. Results In PD, total αSyn levels were increased compared to control subjects [1.76pg/mL (IQR 1.74–1.80) vs 1.73pg/mL (IQR 1.70–1.77), p