Optokinetic nystagmus in artificial hemianopsy.

Optokinetic nystagmus in cases of artificial hemianopsy was studied. Hemianopsy was produced by using a combination of a projector, an erasing device and DC ENG. The effect of the condition of foveal vision in hemianopsy, whether reserved or involved, was discussed. When foveal vision was reserved, nystagmus during stimulation in cases of hemianopsy was essentially the same as in the normal eye. In cases of hemianopsy in which foveal vision was involved, there was a remarkable difference between the mystagmus induced by foveofugal stimulation and that induced by foveopetal stimulation. In the former case the nystagmus was very fine and irregular, in spite of the fact that the nystagmus was well induced (it was nearly the same as in the normal eye in the latter case). Foveal vision is very important for the formation of the slow component of optokinetic nystagmus. Foveopetal movement of the image on the peripheral retina is very important for the formation of the quick component. Foveofugal movement on the peripheral retinal has, on the contrary, only a small effect in attracting the eye.