CHAT and Parkinson disease: In the GCL, the number of ChAT amacrine cells was also strongly reduced (P < 0.0001) in PD, affecting most of the eccentricities analyzed, with a statistically significant reduction from 4 to 10 mm from the optic nerve (P < 0.05 in each region), although the tendency was observed throughout the whole retina (Fig. 2l, Additional file 1: Table S2).