If an intracranial expansive process is suspected clinically, pneumoencephalography forms an excellent method of surveying the optic pathways from the occipital poles to the anterior clinoid processes. Planography during pneumoencephalography, with the patient recumbant, brow up, will permit accurate evaluation of the position of the optic chiasm and in many instances will demonstrate normal as well as pathological optic nerve and chiasm tumors.
Hanafee WN, Lecky JW. Planography During PneumoencephalographyThe Diagnosis of Lesions Affecting the Optic Pathways. Arch Ophthalmol. 1968;80(2):161-165. doi:10.1001/archopht.1968.00980050163002