Applied Anatomic Study on Decompression of Optic Canal through Orbital Approach

Objective:To provide microanatomical data for the decompression of optic canal through observing the structures of canalis opticus and its surrounding.Methods:The optic canals of 50 adult dry cranial bones (100 sides) were dissected under microscope,the relationships between optic canal and ethmoid sinus and sphenoid sinus were observed;the following parameters,including lengths of optic canal walls; the vertical and transverse diameters of orbital and cranial outlet of the optic canal,were measured.Based on measurements of diameters,the corresponding areas were calculated.The position relation among the falciform folds in cranial outlet of optic canal,the inner segment of cranial nerve and arteria ophthalmica,were observed on 15 adult cadaver heads fixed by formalin.Results:the medial wall of canalis opticus was longest with average of (10.71±2.12)mm;the orbital outlet of optic canal present as a longitudinal oval with transverse section area of (25.84±5.43)mm2,the cranial outlet of optic canal appeared a transverse oval with transverse section area of (24.86±4.37)mm2.Conclusions:The optic canal should be opened along its medial wall during operation.The decompression of orbital open must be thorough.Whether the optic nerve sheaths should be opened or not depends on the intraoperative condition.The sectioning should be avoided damaging the nutrient vessel of cranial nerve;the super medial wall is the safe place to be opened.