Amyloid and tau pathology are detectable in the retina in AD (Hart et al., 2016; Koronyo et al., 2017), and the cells which provide photic inputs from the retina to the circadian system, the intrinsically photosensitive retinal ganglion cells (ipRGCs), are decreased in AD (La Morgia et al., 2016). Here, MAPT is linked to Alzheimer disease.