Abstract
PurposeTo determine whether people with central field loss (CFL) from macular degeneration have improved ability to recognize a particularly difficult spatial configuration embedded in noise, the peripherally-viewed ‘ladder contour’. The visibility of these configuration has been linked to general contour integration ability and crowding limitations in peripheral vision.MethodsWe used a trial-based yes-no task. CFL patients and normally-sighted controls performed the task, looking for ladder contours embedded in a field of randomly oriented Gabor patches, at a range of stimulus presentation times (varying stimulus difficulty). Viewing eccentricity in CFL patients was set by their preferred retinal loci (PRLs) and matched artificially in the control group. The contours were presented so as to be tangent to the CFL region, given a patient’s PRL location.ResultsCFL and normally-sighted groups performed similarly on the task. The only significant determinant of performance was the viewing eccentricity.ConclusionsCFL patients do not seem to develop any improved ability to recognize ladder contours with their parafoveal retina, which suggests that there is no underlying improvement in contour integration or reduction in crowding limitations in the region of the PRL despite extended daily use.
Highlights
Macular degeneration deprives a large portion of primary visual cortex of input
Central field loss (CFL) usually occurs well after the critical phases of visual development, and it seems that the deafferented portion of visual cortex is not recruited by other parts of the visual system
In light of numerous findings in the field of perceptual learning, it seems that CFL patients, who typically come to rely on a particular region of still-functioning retina, the preferred retinal locus (PRL) [7], to explore and examine scenes, might be expected to gain some benefit from training of parafoveal retina that people with intact central vision do not receive[8,9,10]
Summary
Central field loss (CFL) usually occurs well after the critical phases of visual development, and it seems that the deafferented portion of visual cortex is not recruited by other parts of the visual system. There have been some reports of “reorganization” of deafferented visual cortex [1,2,3,4,5], but it is unclear whether or not this reorganization is an adaptive response by the visual system that yields some visual benefit, or a side effect of deafferentation [2,4,6]. The question, is what visual task might reveal the possible benefits of early visual system reorganization in response to CFL
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