vision missing in the lateral, temporal half ofboth visual fields. Caused by compression of the optic nerve at the optic chiasm, affecting the bilateral medial retina. Most often due to tumors of the pituitary that are forced to expand upward because of the bony "saddle" they sit in, the sella turcica, or turkey saddle. Here you see an interesting example direct from the number one most frequently used medical resource, wikipedia. This example shows two views of Paris. The second obviously with bitemporal hemianopsia. Loved these pictures, and love wiki, so had to post them. Enjoy.