[Hemianopic visual field defects--methods of study and localization problems]

Abstract

In a survey of methods for determining hemianopic visual field defects, a distinction is made between gross visual field screening and actual visual field examination with kinetic and automatic static perimetry. These methods may be arranged according to increasing the concentration required as well as to ability to cooperate, as follows: hand-movement stimulation of shifts of gaze, finger-counting with repetition by the patient, brightness and color comparison among the respective halves and quadrants of the visual field, then kinetic perimetry with the Goldmann perimeter, and, most exacting of all, automated perimetry. The advantages of kinetic perimetry in cases of incipient bitemporal visual field defects are discussed. For visual field examination with automated static perimeters, test programs are chosen which have their test-point pattern shifted with respect to the principal meridian. The diagnostic situations in which visual field testing may and must not be limited to 30 degrees are presented in tabular form. Guidelines and criteria for localizing lesions have been developed, i.e., the vertical and horizontal limits of the major axes which pass through the fixation point and the temporal crescent. Consideration of the course of the nerve fibers in the retina and of the fact that exact separation between superior and inferior may only be found temporal to the foveola with corresponding nasal defects enables horizontally limited visual field defects originating within the eye to be distinguished clearly from those originating in the visual cortex. Vertical limits due to semidecussation at the chiasma permit a differentiation between prechiasmic and postchiasmic lesions. In homonymous defects, consideration of further simple anatomic features of the visual pathway, namely the knee of Wilbrand and that portion of the optic radiation which extends anteriorly to the temporal lobes and which represents the inferior retinal halves with characteristic defects, also enables lesions in the visual pathway to be localized more accurately.