Anatomic considerations for computed tomography of the optic chiasm.

When the clinical distinction between lesions of the optic nerves or the chiasm is not apparent, computed tomographic scans should be performed at both 0 degrees and 25 degrees or 35 degrees to the orbital-meatal line (Reid's baseline). The former plane is preferable for the demonstration of the optic nerves or orbital structures, while the latter allows superior visualization of perichiasmatic structures.