A comparative study of scanning electron microscopy (SEM) and atomic
force microscopy (AFM) imaging of the healthy human optic nerve was
carried out to determine the similarities and the differences. In this
study we compared the fine optic nerve structures as observed by SEM and
AFM. The fibers of the right optic nerve of a 61-year-old man show
different arrangements in transverse sections taken from the same
individual 5 mm central to the optic canal and 5 mm peripheral to the
optic chiasma; this difference can be recognized by light microscopy (LM),
SEM, and AFM. AFM revealed such typical optic nerve fibers (taken from a
point 5 mm central to the optic canal) with annular and longitudinal
orientations, which were not visible by SEM in this form. By contrast, LM
and SEM visualized other structures, such as pia mater and optic nerve
fibers loosely arranged in bundles, none of which was visualized by AFM.
The images, however, taken 5 mm peripheral from the optic chiasma show
shapeless nerve fibers having a wavy course. Our results reveal that more
detailed information on optic nerve morphology is obtained by exploiting
the advantages of both SEM and AFM. These are the first SEM and AFM images
of healthy human optic nerve fibers, containing clear representations of
the three dimensions of the optic nerve.