Microsurgical anatomy of the optic canal and its clinical significance

Objective: To provide detailed knowledge of this region for optic nerve decompression and further understanding to the pathologic mechanisms of indirect optic nerve injurey.Methods: 60 optic canals and optic nerves in the 30 fixed human cadaver heads were observd and measured under the operating microscope.The calibres of the canal and intracanalicular optic nerve, the length and thickness of canal wall, the canal transverse area and optic nerve transverse area were measured and calculated.Results: The middle part of the medial wall of bony canal is the thinnest, with a thickness of 0.48±0.36 mm.The middle part of the optic canal was the narrowest, with a transverse area of 17.47± 3.97 mm 2.The axis of the optic canal and middle saggital plane of skull formed an angle of (37.46±1.66)°, and the angle formed by the axis of optic canal and the horzontal plane of the skull was (21.00±3.46)°. Conclusion: Since in the middle part where the restraint on injured nerve may be the most intensive, the middle part of the optic canal may be critical in optic nerve decompression.The features of the optic canal′s pathway was an important anatomical factor that indirect optic nerve injury was usually resulted from a blunt trauma to the frontotemoral region.