CD68 and Alzheimer disease: First, we observed that the proportion of the microglia containing CD68 labelling (CD68+) was simlar between the AD and control retina (Fig. 6B; machine control: 88.12 ± 1.229 (mean ± SEM); machine AD: 92.46 ± 3.488% (mean ± SEM); p = 0.2857).