Morphometric analysis of the fascicular organisation of the optic nerve.

BACKGROUND: The optic nerve is anatomically observed in four segments: 1) the intrabulbar, 2) the orbital, 3) the canalicular, and 4) the cranial. According to the literature, the surfaces of the transversal cut of the nerve is different throughout it. OBJECTIVE: The purpose of this study is to evaluate the fascicular organisation of the optic nerve, throughout its three segments from the eye. METHOD: Five pairs of optic nerves were examined, obtained from the autopsies. Using a Heidenhain's (azan) staining, the cuts were prepared for microscopy. A morphometric analysis was performed by stereological methods for morphometric cytology – Weible's testing system M42. The following measures were established: the surface of the transverse cut of the nerve, the entire surface of the fasciculi, the entire surface of the connective tissue and the blood vessels, the number of fasciculi, the surface of a single fasciculus. RESULTS: The results of the study have demonstrated significant differences between the examined parameters of the different parts of the nerve. DISCUSSION: The surface of the transverse cut of the nerve was found to have grown from the orbital to the cranial segment, as well as the entire surface of the fasciculi. While their number is significantly lower in the cranial segment, the number of the fasciculi varied slightly between the orbital and the canalicular segment. The surface of a single fasciculus grew from the bulb to the chiasma. There is probable cause to believe that this may be due to fusion of the "small" fasciculi in the orbitocranial direction.