APOE and Schnyder corneal dystrophy: As shown by Jessen et al. [6] for the SCD-syndrome as a potential pre-prodromal stage in AD, the likelihood of preclinical AD in individuals with SCD is increased by the following features: SCD onset within the last 5 years, age at onset ≥60 years, confirmation of cognitive decline by an informant, presence of the APOE ε4 genotype, and biomarker evidence for AD.