MAPT and Alzheimer disease: In the current study, we use the p-tau-specific thiophene-based ligand bTVBT2 to investigate the relationship between disease progression and p-tau uptake by microglia in the retina of AD patients and AppNL−F/NL−F knock-in mice, an AD mouse model known to demonstrate extracellular Aβ plaques and dystrophic neurites in the brain from 6 months of age.