Metrizamide optic nerve sheath opacification.

The safety of metrizamide in the optic nerve sheath has not been studied to our knowledge. We studied histologic changes produced by metrizamide in the optic nerve of cats with surgically created lesions simulating orbital tumors and trauma. Displacement, compression, and disruption of the optic nerve sheath were detectable by radiographing the opacified sheath. Arachnoiditis of the optic nerve sheath is unlikely from a single exposure to metrizamide in a concentration less than 300mg I/ml.