The basis of microsurgical anatomy of optic nerve decompression

Objective:To provide the basis of microsurgical anatomy for optic nerve decompression.Methods:The adjacent structures of optic nerve and ophthalmic artery were observed and measured on 26 sides of formalin fixed cadaver heads.Results:A plica,which was formed by the fusion of the outer membrane of optic nerve sheath with the dura of superior orbital fissure,extended into the orbital cavity,with the thickness of(1.71±0.37)mm(1.14～2.38 mm).88.5% Ophthalmic arteries entered the sheath at the medial bottom of the cranio-aperture of the optic nerve canal,and ran into the orbital cavity at the medial side of the anterior part of plica.The optic nerve-internal carotid artery recess was formed by the inferior-lateral wall of orbital tube and lateral wall of the sphenoidal sinus,with the length of(7.40±1.44)mm(5.60～10.10mm).Conclusions:1.The optic nerve sheath should be incised along the medial-superior wall during decompression.2.The decompression should be extended 1.14～ 2.38 mm into the orbital cavity in addition to the exposure of the whole length of the bony optic nerve canal,if ophthalmic artery decompression was intended.3.The optic nerve-internal carotid artery recess can serve as a surgical landmark in optic nerve decompression.