[CT anatomic measurement of the optic canal and its clinical significance].

OBJECTIVE: To probe into the normal anatomy of the optic canal and its clinical significance. METHODS: The optic canals of 200 normal subjects were examined by thin layer CT scan in axial nd coronal positions. The distance and anatomic relationship with circumferentral structure were measured. RESULTS: In average: (1) The transverse diameter of the optic canal was (3.57 +/- 0.61) mm, the longitudinal diameter was (4.82 +/- 0.38) mm, the length of the inner wall was (12.62 +/- 2.59) mm, the length of the outer wall was (10.18 +/- 2.19) mm, and the length of the optic canal was (11.46 +/- 2.35) mm. The angle between optic canal and the middle line of the skull was 34.34 degrees +/- 6.48 degrees, the angle between optic canal and the intraorbital optic was 10.69 degrees +/- 6.48 degrees. The thickness of the inner wall was (0.68 +/- 0.46) mm. It showed no significant difference between the two sides of the optic canal in diameters(P > 0.05). (2) The optic canal, the superior orbital fissure and the inferior orbital fissure were respectively shown as track, crack and gorge type in CT axial pictures, while in the coronal pictures, they were respectively shown as butterfly eyes, horizontal fissure and vertical fissure type. (3) The relationship of the posterior ethmoid sinus and the optic canal was: anterocanal(42.00%), semicanal(27.5%), whole-canal(18.75%), sella turcica(9.75%) and circumcanal(2.00%). (4) The relationship of the position of the sphenoidal sinus and the optic canal was: I degree sphenoidal sinus(20%), II degree (63%) and III degree (17%). (5) The incidence of the bony defect of the inner optic canal wall was 25.5%. The range of the defect was (5.07 +/- 2.52) mm. CONCLUSION: It's a reliable way to show the relation of the optic canal and circumcanal by CT, and it is of important value in operation.