The optic nerve in the posterior ethmoid in Asians.

Anatomical dissections employing the endoscopic sphenoethmoidectomy technique were performed in 51 fresh Asian cadaveric heads. Specific data concerning the anatomical variations of the posterior ethmoid sinus and its relationships to the optic nerve were recorded. Approximately two-thirds (65%) of the specimens showed a direct relationship between the optic nerve and posterior ethmoid sinus. Posterior ethmoid cells with an optic canal bulge were found in 50.98% of the 102 sides dissected. In 14.7% no optic canal bulge was present, yet the optic nerve was intimately related to the posterior ethmoid sinus. In this latter group, the average thickness of bone separating the optic nerve from the posterior ethmoid sinus was 0.25 mm. The authors consider that in endoscopic sinus surgery, this type of relationship is potentially the most hazardous to the optic nerve.