In the same study, histological analysis based on immunofluorescent staining or 3,3′-Diaminobenzidine staining and the use of specific monoclonal antibodies recognizing diverse Aβ epitopes revealed intense deposition of both Aβ42 and Aβ40 in AD retinal vasculature (n = 28–36 human samples). In addition, early loss of pericyte marker PDGFRβ was noted in longitudinal and vertical retinal vessels of MCI and AD patients compared to normal controls (n = 38). The dramatic loss of vascular PDGFRβ expression significantly correlated with CAA (n = 14) and Mini-Mental State Examination (MMSE) cognitive scores (n = 10) in a subset of patients, suggesting that retinal pericyte and PDGFRβ loss could predict the cerebral vascular disease and cognitive function. Further TUNEL and cleaved caspase-3 staining demonstrated that apoptosis may be the dominant pathway of retinal pericyte death in MCI and AD retina.