[Experimental study on anatomy of adjacent structures of the optic canal].

OBJECTIVE: To provide microanatomical data for optic canal decompression surgery or paranasal sinus surgery through anatomical study on adjacent structures of the optic canal. METHODS: It was a experimental study. (1) Fifty dry cadaveric adult heads (100 sides) were dissected. The shapes and sizes of ethmoid sinus and sphenoid sinus were observed and measured. (2) The distance between the mid-point of the lateral wall of the sphenoid sinus and the internal carotid artery, the angle between the initial section of the ophthalmic artery and internal carotid artery were observed and measured under both naked eye and microscope. The distance between the medial margin of bilateral optic nerve at the frontal outlet were measured on 15 formalin-fixed wet cadaveric adult heads. The relationships between the optic canal and ethmoid sinus and sphenoid sinus were observed on 6 formalin-fixed cadaveric adult heads by CT scanning; the morphological features and adjacent structures were contrasted and observed on 6 ice-frozen cadaveric head specimens by CT scanning and corresponding applied sectional anatomy. RESULTS: The anterior-posterior diameter of total ethmoid sinus was (39.02 +/- 4.89) mm. The horizontal diameter of anterior ethmoid sinus was (12.26 +/- 2.12) mm. The superior-inferior diameter of anterior ethmoid sinus was (11.89 +/- 2.56) mm. The anterior-posterior diameter of sphenoid sinus was (24.08 +/- 4.87) mm. The distance between the middle part of the lateral wall of sphenoid sinus and internal carotid artery was (1.23 +/- 0.56) mm; the angle between the initial section of ophthalmic artery and internal carotid artery was 54.33 degrees +/- 7.89 degrees . The distance between the medial margin of bilateral optic nerve at the frontal outlet was (14.26 +/- 3.23) mm. CONCLUSIONS: (1) When the medial wall of the optic canal is opened inside the sphenoid sinus, the depth shouldn't exceed 13 mm, otherwise it may damage the internal carotid artery and cause severe bleeding even death. (2) The depth should be less than 15 mm and the superior-inferior diameter should be less than 12 mm inside the anterior ethmoid sinus, otherwise the opposite ethmoid sinus or frontal base may be opened accidently. (3) The ophthalmic artery should be specifically protected in order not to cause ocular ischemia and blindness.