Indeed, the percentage of RGC neurons positive for OPN (Figure 5A, left) was significantly higher in AD respect to control retinas (AD: 84 ± 5%, n = 36/6 fields/patients; CTRL: 63 ± 6%, n = 34/6 fields/patients; p < 0.01; Figure 5C). This evidence concerns the gene SPP1 and Alzheimer disease.