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Julian M. Wallace, Susana T. L. Chung, Bosco S. Tjan; Crowding in individuals with age-related macular degeneration. Journal of Vision 2012;12(9):336. doi: 10.1167/12.9.336.
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© ARVO (1962-2015); The Authors (2016-present)
People with age related macular degeneration (AMD) who lose their central visual field must rely on peripheral vision for their daily activities, which is often difficult. One reason for this difficulty is the crowding effect, which impairs object recognition in a cluttered environment and is prominent in normal peripheral vision. However, there is little published data about crowding in AMD patients. The present study examines how crowding affects object identification in 3 AMD patients with varying degrees of visual deficits, and compares their performance to that for 6 elderly controls and 3 younger subjects. We measured contrast thresholds for an object identification task over a range of target and tangential flanker separations using QUEST. Targets and flankers were photographs of objects, and were presented above the size acuity estimated for each subject at the eccentricity tested. AMD patients viewed the stimulus with their preferred retinal locus (PRL) with unlimited viewing time. Control subjects were tested with a similar procedure at an eccentricity matching one of the three patients (two elderly controls and one young subject per patient). Target eccentricity was maintained during unlimited viewing using an eye tracker to present the stimulus only when subjects were accurately fixating. We found no clear difference in contrast threshold elevation as a function of target-flanker spacing between the AMD patients, elderly controls, and younger subjects. Although the younger subjects’ contrast thresholds tended to be lower overall, the magnitude of crowding in terms of threshold elevation and its spatial extent were remarkably similar between all groups. The present findings suggest that crowding does not diminish or worsen with age. Further, patients who have developed a PRL remain affected by crowding, showing little evidence of ‘uncrowding’ due to learning, at least for the limited case of tangential flankers.
Meeting abstract presented at VSS 2012
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