To determine the existence of synaptotoxic AβO [68, 98] in the human retina, cross-sections were labeled for the neuronal-specific βIII-tubulin marker with a conformation-sensitive and sequence-specific antibody, in the format of a single-chain Fv fragment (scFv), selectively recognizing AD-relevant AβOi species [74, 75, 97]. This evidence concerns the gene ABO and Alzheimer disease.