Spatial Cognition in Glaucoma: Constricted Field of View Weakens the Perception of Global Configurations

We tested whether the global precedence effect shifts towards local precedence when the visual field is reduced by glaucoma. Fifteen patients, 15 age-matched and 15 young controls were presented with compound letters and asked to recognize a target letter occurring randomly at the global (target-large) or at the local (target-small) level. Small stimuli elicited a global precedence effect in all three groups with shorter response times for target-large than for target-small but accuracy was at chance for target-small in patients. Large stimuli produced a shift towards a local precedence effect with shorter response times for target-small than for target-large in all three groups but accuracy was at chance for target-large in patients. The results suggest that glaucoma impairs perception at different spatial scales. The recognition of small letters in the fovea is affected by crowding. The recognition of global configurations is impaired by reduced sensitivity in the peripheral visual field.