MAPT and Alzheimer disease: Regarding tauopathy, a wide range of abnormal tau isoforms have been identified in the retinas of AD patients, including pretangles and mature tangle forms: 3- and 4-repeat tau, p-tau, and citrullinated tau forms, oligomeric tau (Oligo-tau), paired helical filaments of tau (PHF-tau), as well as paperclip folding of tau and NFT-like structures [28, 30, 40, 45, 46, 63, 89, 112, 129].