APOE and Schnyder corneal dystrophy: Thus, the objectives of this study were (1) to identify cross-sectional differences in peripheral blood NCAPH2 methylation among patients with SCD and objective cognitive impairment (OCI) relative to normal control (NC) participants and (2) to identify the correlation between the hippocampal volume, the cognitive function, and the NCAPH2 methylation levels and their interaction with the APOE ε4 status.