TUMORS at the optic chiasm may produce defects in visual fields by interruption of blood supply, by direct pressure of the tumor, or by forcing the optic nerves or chiasm against firm neighboring structures, such as the margins of the optic canals or the arteries of the circle of Willis. The last circumstance appears to account for many of the defects in the lower portion of the field encountered relatively late in the course of tumors in this region. On the other hand, the upper bitemporal hemianopsia that appears early may be attributed to direct pressure against the anterior margin of the chiasm and interference with its blood supply.
SURVEY OF LITERATURE
Notching of the optic nerves at their junction with the chiasm by arteries of the circle of Willis was recognized by Tiirck1 a century ago. His description may be translated as follows:In the corpse of a
RUCKER CW, KERNOHAN JW. NOTCHING OF THE OPTIC CHIASM BY OVERLYING ARTERIES IN PITUITARY TUMORS. AMA Arch Ophthalmol. 1954;51(2):161-170. doi:10.1001/archopht.1954.00920040163002