The AUC of NCAM/ABCA1 dual-labeled exosomal Aβ42/40 for diagnosis of SCD was higher than that of Aβ42, T-tau, and P-T181-tau; the AUC of NCAM/ABCA1 dual-labeled exosomal miR-384 for diagnosis of SCD was higher than that of Aβ42, Aβ42/40, T-tau, P-T181-tau, and NfL.miR-384 can downregulate the expression and activity of BACE. The gene discussed is NCAM1; the disease is Schnyder corneal dystrophy.