Objective: To compare oligomeric alpha-synuclein (α-Syn) in reflex tears and its association with the thickness of retinal layers in Parkinson’s disease (PD)

Background: Alpha-synuclein is a protein implicated in the neuropathogenesis of PD and accumulates in the retina. The oligomeric aggregates are found in tears and represent the most neurotoxic form of α-Syn

Method: In this cross-sectional study we included 50 eyes of 25 PD subjects and 76 eyes of 38 healthy controls (HC). Oligomeric α-Syn in reflex tears was measured using the human oligomeric α-Syn ELISA kit. Retinal layer thickness was measured using a spectral domain optical coherence tomography. Mann-Whitney-U-Test and Spearman rank correlation coefficient were used for analysis. Statistical differences were considered significant if p <0.05.

Results: Individuals mean age was 62.8±14.1 years old in PD and the mean disease duration was 9.7±8.8 years. The mean oligomeric α-Syn levels in tears were higher in PD in comparison with HC [1.77 (95% CI, 1.75-1.80) vs 1.73 (95% CI, 1.69-1.74), p<0.001]. The nerve fiber layer, ganglion cell layer, internal plexiform layer, inner nuclear layer, outer nuclear layer, and retinal pigment epithelium were thinner in comparison with controls (p<0.05). The outer plexiform layer had higher thickness in PD. A positive correlation between oligomeric α-Syn levels and the central volume of inner nuclear layer (r=0.404, p=0.04) was observed

Conclusion: We found a significant difference of oligomeric α-Syn reflex tear level when compared PD patients to healthy controls. Furthermore, we observed a thinner inner retinal layers and thickener outer retinal layers in PD when compared to controls. The positive correlation between oligomeric α-Syn levels, and changes in the inner retinal nuclear layer point out into a potential diagnostic tool for PD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/oligomeric-alpha-synuclein-in-reflex-tears-and-retinal-changes-in-parkinsons-disease/