Since Jackson and Gowers1 in 1874 called attention to the importance of perimetry in neurologic examinations, it has been known that changes in the visual fields may supply important information as to the general and, at times, the specific location of a lesion of the brain. For example, bitemporal hemianopia, when present, definitely places the lesion at the optic chiasm. When homonymous hemianopia exists the lesion is definitely lateralized on the opposite side, but it may be located at any site along the visual pathway between and including the visual center in the occipital lobe and the chiasm.
In my work at the Neurological Institute of New York sectoral and other incomplete homonymous defects of the visual fields have often seemed to me to have definite localizing significance, and when other symptoms have been correlated with the homonymous changes in the fields the localization of expanding lesions of