NEFL and Schnyder corneal dystrophy: In the whole sample, NfL levels were significantly correlated with age at onset and with age at baseline in SCD (Spearman’s ρ 0.364, p = 0.040 and Spearman’s ρ 0.529, p = 0.001, respectively) and MCI (Spearman’s ρ 0.416, p = 0.004 and Spearman’s ρ 0.550, p < 0.001, respectively) groups but not in AD (Fig. 2).