Misidentifying a tennis racket as keys: object identification in people with age-related macular degeneration.

PurposePrevious studies showed that people with age-related macular degeneration (AMD) can categorise a pre-defined target object or scene with high accuracy (above 80%). In these studies participants were asked to detect the target (e.g. an animal) in serial visual presentation. People with AMD must rely on peripheral vision which is more adapted to the low resolution required for detection than for the higher resolution required to identify a specific exemplar. We investigated the ability of people with central vision loss to identify photographs of objects and scenes. MethodsPhotographs of isolated objects, natural scenes and objects in scenes were centrally displayed for 2s each. Participants were asked to name the stimuli. We measured accuracy and naming times in 20 patients with AMD, 15 age-matched and 12 young controls. ResultsAccuracy was lower (by about 30%) and naming times were longer (by about 300ms) in people with AMD than in age-matched controls in the three categories of images. Correct identification occurred in 62-66% of the stimuli for patients. More than 20% of the misidentifications resulted from a structural and/or semantic similarity between the object and the name (e.g. spectacles for dog plates or dolphin for shark). Accuracy and naming times did not differ significantly between young and older normally sighted participants indicating that the deficits resulted from pathology rather than to normal ageing. ConclusionsThese results show that, in contrast to performance for categorisation of a single pre-defined target, people with central vision loss are impaired at identifying various objects and scenes. The decrease in accuracy and the increase in response times in patients with AMD indicate that peripheral vision might be sufficient for object and scene categorisation but not for precise scene or object identification.