Figure 5.

(A) Number of degenerated axon profiles relative to number of healthy axons in each optic nerve quadrant using criterion 1. Each quadrant of the implanted and RP-affected right eye showed high ratios of degenerated axon profiles to healthy axons compared to respective quadrants in the fellow left optic nerve, RP controls, and normal controls. This eye had more advanced RP disease and prior acute stimulations. However, the temporal optic nerve quadrant which corresponded to the site of epiretinal array implantation and stimulation (marked with *) had a low ratio when compared to other quadrants within the same optic nerve. The degenerated axon profiles represent an intermediate-to-late stage of an ongoing aging and/or disease process during which axons are slowly digested by macrophages and eventually removed from the nerve. (B) Number of degenerated axon profiles (including macrophages) relative to number of healthy axons in each optic nerve quadrant using criterion 2. Even though criterion 2 was more inclusive with both total axon and degenerated axon (and thus had slightly different absolute ratios compared to criterion 1), the two data sets still showed striking similarities in the overall pattern.