Ultrastructure of Aβ deposits in AD retina identified by transmission electron microscopy (TEM). (A–B’) Representative TEM images of retinal cross-sections from definite AD patients showing (A) ultrastructure of Aβ plaque (pl), fibrils (fib) and protofibrils (pfib) near a blood vessel (bv). Scale bar: 1 μm. (A’) High-magnification image showing Aβ fibrils, protofibrils and Aβ deposits (abd). Scale bar: 50 nm. (B) Aβ plaque-like deposits (pl; demarcated by red line), near basement membrane (bm) of a blood vessel (bv). Scale bar: 0.5 μm. (B) High magnification image of region marked by red asterisk in (B) showing dense Aβ deposition with structural similarity to annular oligomers (red arrowhead). Scale bar: 40 nm. All sections were prestained with anti-Aβ42 mAb (12F4) and peroxidase-based system and DAB substrate chromogen. Reproduced from Koronyo et al. (2017) with permission of ASCI via Copyright Clearance Center.