It is interesting that as AD advances there is a progressive and sequential elevation in the pro-inflammatory gene expression marker COX-2 from the limbic system (where AD originates) into the primary visual cortex and retina, and this is accompanied by parallel elevations in Aβ 42 peptide abundance and inflammation across the entire entorhinal-primary visual cortex-thalamic-retinal axis (Cui et al., 2007; Kruck et al., 2008; Fang et al., 2009; Alexandrov et al., 2011; Cao et al., 2013; Cudaback et al., 2014). This evidence concerns the gene PTGS2 and Alzheimer disease.