The relationship between a DTI-based measures, FA, and a microscopic measurements, densities of axons. (A) Sections of optic nerve immunohistochemically stained for phosphorylated neurofilaments (NF), in each side of the control (C-ON) and the glaucomatous optic nerve (G-ON), for each animal (#1–5). The density of NF was almost comparable to that of the contralateral control in the ocular hypertensive animal (#1), mildly decreased in the early stage glaucoma animal (#2), and severely degraded in advanced stage animals (#3–5). See Additional file 5: Table S5 for quantified data for each optic nerve. (B) A plot of FA values and the number of axons in the optic nerve. Values are ratios of the measured value in the glaucomatous side to that in the non-affected side. The numbers of axons were evaluated in transaxial sections of optic nerve stained with toluidine blue. (C) The relationship between DTI-based FA values (x-axis) and the microscopically-counted NF density (y-axis) in the glaucomatous (G-ON) and control optic nerve (C-ON). See also Additional file 5: Table S5 and Table 2.