Density of mitochondrial profiles in ON vulnerable to secondary degeneration +/− R/NIR-IT. (A) Transverse section (semi-thin) of an ON lesion site, stained with 0.5% toluidine blue. The black bars are a schematic of the copper grid overlaying ultrathin sections and the arrow represents the path taken during sampling from one ventral region, bounded by the grid; scale = 50 μm. (B) Representative electron micrograph illustrating definition of axonal and glial cellular compartments, tracing of glial processes is shown in green. Diameters of mitochondria were measured at the longest extent and a second measurement perpendicular to the first through the midline was made for assessment of mitochondrial ellipticity (red). Area was measured by manually tracing around the outer membrane (yellow); scale = 1 μm. (C) Representative images illustrating criteria for classification as mitochondria ie: double membrane, increased electron density and/ or convolutions (black arrows) or excluded due to lack of double membrane (red arrow); scale = 1 μm. Mean densities of mitochondrial profiles did not change with injury or R/NIR-IT in axons (D) or glia (E), p >0.05. Black dots represent means for each animal and the red line indicates the group mean.