Fig. 2.

Spearman correlation between each marker in tears and ROC curves for distinguishing PD patients from controls. a Spearman correlation of the tear fluid levels of α-synuclein and NfL in all participants. b The prediction accuracy for the occurrence of PD, as expressed by the area under the curve (AUC), improved from 0.61 in the basic model containing age and sex only (P = 0.062) to 0.69 with the addition to the model of either tear fluid levels or the retinal vascular densities VDdM or VDrID. The AUC further increased to 0.75 in the full model containing age, sex, tear fluid levels of α-synuclein and NfL, and the retinal vascular densities VDdM and VDrID (P < 0.001)