Visual field rehabilitation in the cortically blind?

Investigators have recently reported that specific practice facilitates the restitution of visual fields in partially blinded humans with lesions to the striate cortex. In order to further evaluate this work, attempts were made to retrain twelve homonymous hemianopic or quadrantanopic patients with similar methods, but under conditions in which possible contaminating experimental variables were controlled, including: reliance on gross subjective impressions, large visual stimuli response variability, changes in detection strategies with practice and compensatory eccentric fixation. The results indicate that visual field increases are not trainable. It is concluded that previous studies should be regarded with caution and the restitution of visual fields after damage to the striate cortex in humans is probably not possible with existing methods.