The findings between two groups showed the following: (1) the PD-SCD patients indicated significantly decreased FC in bilateral PoCG, right MOG, right SOG, and bilateral PreCG than the PD-NC patients (TFCE-FWE corrected p < 0.05; Figure 3c; Supplementary Table 1); (2) the PD-MCI group showed significantly reduced FC in right PoCG, right SPG, and PreCG than the PD-NC group (TFCE-FWE corrected p < 0.05; Figure 3d; Supplementary Table 1); (3) the PD-MCI group illustrated significantly elevated FC in right MOG than the PD-SCD group (TFCE-FWE corrected p < 0.05; Figure 3b; Supplementary Table 1). Here, MOG is linked to Schnyder corneal dystrophy.