Residual vision in transition zones in patients with cerebral blindness

Using high resolution perimetry in repeated sessions, we investigated 27 pa tients with homonymous visual held defects in order to detect islands of vi sion within the damaged area, and to determine color- and form-recognition abilities within these zones of residual vision. In most patients we found circumscribed areas within the "blind" field in which the stimulus was dete cted in about 50% of presentations. Only one patient had an island of visio n greater than 5 degrees within the defective area. We also found an area o f variable performance between the blind and the intact field. Borders of f ield defects were classified as being: (a) sharp (small transition zone), ( b) medium, or (c) fuzzy (scattered deficits). We propose that transition zo nes are functional representations of partially spared neuronal structures in areas of the brain which are only partially injured.