Retinal pathology in Alzheimer's disease .2. Regional neuron loss and glial changes in GCL

Detailed analyses of neuronal and astrocyte cell numbers in the ganglion cell layer (GCL) of whole-mounted peripheral retinas from 16 Alzheimer's disease (AD) and 11 control eyes (11 and 9 cases, respectively) demonstrate extensive neuronal loss throughout the entire retina in AD as compared to control eyes. The observed neuronal loss is most pronounced in the superior and inferior quadrants, ranging between 40 and 49% throughout the midperipheral regions, and reaching 50-59% in the far peripheral inferior retina, while the overall neuronal loss throughout the entire retina amounts to 36.4% (p < 0.004). Although the 16% increase in astrocyte numbers is not significant, the ratio of astrocytes to neurons is significantly higher (82%; p < 0.0008) in AD as compared to normal retina (0.238 +/- 0.070 vs. 0.131 +/- 0.042). These results are strengthened by the close agreement (within +/- 15% of respective means) found between fellow eyes. Analysis of glial fibrillary acidic protein immunoreactivity (GFAP-ir) in sections of retinas from an additional 12 AD and 19 control cases show increased GFAP-ir with more extensive labeling of astrocytes in the GCL as well as increased labeling of Muller cell end-feet and radial processes in AD as compared to control retinas. The extensive loss of neurons documented in these retinas, accompanied by an increased astrocyte/neuron ratio, provides further support for the substantial involvement of the retina in AD.