The optic nerve can be damaged by penetration of the orbit through the lamina papyracea (Fig. 12.20). If the assistant looks out for eye movement when the surgeon is operating on the lateral nasal wall, it is unlikely that the nerve could be damaged before it was noted that the orbit had been entered.
The other means by which the optic nerve can be traumatized is if it is exposed in a sphenoethmoid air cell (Fig. 12.21a, b). A sphenoethmoid air cell should be sought on the CT preoperatively and care should be taken in removing polyps or cells lateral to the sagittal plane of the medial wall of the maxillary sinus. In these circumstances, it is particularly advisable to find the sphenoid sinus medially first of all and then work forward. The optic nerve can be prominent in 20% of patients in the upper half of the lateral wall of the sphenoid sinus, but it is rarely dehiscent. The carotid lies in the lateral and inferior aspect of the sphenoid sinus and it is therefore advisable to avoid the lateral wall of the sphenoid, unless there is good reason (e.g., optic nerve decompression). If a powered shaver is placed in the sphenoid sinus, its suction port should be directed medially to minimize the risk of damaging the structures in the lateral nasal wall.
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