MAPT and supranuclear palsy, progressive, 1: Considering that PSP is a neurodegenerative tauopathy and the RNFL, INL, and IPL layers are part of the IRL, we speculate that accumulation of tau protein in such retinal layers may cause the IRL, GCL, IPL, and OPL degeneration in PSP patients, with possible evolution in retinal thinning [6].