Fig. 5.

Masson's trichrome-stained transverse histological section of retrobulbar ON from a 57-year-old human 1.84 mm posterior to the globe. Collagen stains blue, nerve tissue purple, and acellular protein in the cerebrospinal space pink. (a) The ON sheath is the external blue ring surrounding the light pink of the CSF space that bathes the ON within it. (b) Magnified view of red circle area illustrating the intimate connection between pia and the dense blue network of connective tissue within the ON. It is thus reasonable to model the ON and its incorporated pia and connective tissue as one composite structure.