Following Eye Movements in the Absence of Central Vision

Abstract

Following responses to constant velocity and sinusoidally oscillating movements of the whole visual environment were examined in normal subjects wearing blinkers to obscure central vision or subjected to a photo flash to induce a central scotoma, in patients with central scotomas of pathological origin and in one patient with a central scotoma in an immobile eye which provided open loop testing. Good following and brisk nystagmus were produced in patients with central scotomas and subjects with flash scotomas; it was subjectively evident that the scotoma itself could be used as a target to generate open loop pursuit and augment peripherally induced following responses. Following responses in subjects with blinkers were weak, possibly reflecting that, in everyday life, eye movements induced by movements of the visual background have to be suppressed. Open loop responses were strong, suggesting that the periphery has the latent potential to mediate good following. The findings provide a unified explanation for the various patterns of optokinetic nystagmus.