Abstract
Abstract: :
Purpose: To explore configuration dependency of contrast integration across space in amblyopia. Methods: Contrast detection thresholds (temporal 2AFC, 160 ms each presentation) were measured for 37 amblyopic eyes, with Gabor targets (1.5-12 cpd, 0,45,90,135 deg orientation) in isolation and in the presence of laterally placed (2-9λ from target) high contrast Gabor flankers of the same spatial-frequency and orientation. Targets dimensions (σ) were varied in two different directions, along the local orientation (σy) and orthogonal to it (σx). Results: For varied target size, amblyopic eyes showed extended spatial integration at contrast threshold, following a close to square root summation, regardless of the axis along which size was varied, while normal sighted observers showed only limited integration along the axis orthogonal to the local orientation. For lateral masking, amblyopic eyes showed suppression from flankers at short target-mask separations, up to 3λ distance with collinear configuration and 4.5λ with side-by-side configuration. For larger separations, no consistent effects from flankers were observed. Conclusion: Despite having abnormal spatial integration with high contrast flankers, contrast summation at threshold is almost efficient as in normal sighted observers for collinear configuration but is above normal for the orthogonal configuration. The results suggest that amblyopes process contrast with isotropic integration fields, without a clear segregation between contour integration and texture processes. The larger integration fields may cause loss of spatial resolution (localization and acuity).
Keywords: 368 contrast sensitivity • 579 shape, form, contour, object perception • 586 spatial vision