Abstract
PURPOSE: Contour integration, the process of combining local visual fragments into coherent paths or shapes, is essential for visual perception. Although prior research on amblyopia has focused primarily on spatial domain deficits in contour integration, this study investigates how amblyopia affects contour integration over time and examines the relationship between temporal contour integration deficits and visual functions. METHODS: Nineteen amblyopic children (mean age, 10.9 ± 2.4 years; 17 anisometropic, 2 anisometropic/strabismic mixed) and 26 visually normal children (mean age, 10.5 ± 1.8 years) participated in this study. Temporal contour integration was assessed by measuring the accuracy of detecting tilted contour paths, formed by collinear Gabor elements with similar orientations, under slit-viewing conditions. Performance was evaluated for amblyopic eyes (AEs) and fellow eyes (FEs) at two spatial frequencies (1.5 cpd and 3 cpd). The slit width, orientation jitter of contour elements, and stimulus movement speed were systematically varied across separate runs. Visual acuity and Randot stereoacuity were assessed before testing. RESULTS: AEs exhibited significant deficits in temporal contour processing compared with FEs. Specifically, AEs required larger slit widths to achieve performance levels comparable to FEs, with more severe amblyopia (i.e., worse AE visual acuity) necessitating even larger slit widths for temporal contour integration. Temporal contour integration deficits in AEs were most pronounced under conditions of complete Gabor collinearity or moderate stimulus movement speeds (6.4°/s). No significant differences were observed between FEs and control eyes. Notably, the temporal contour integration ability between the two eyes quantified as the AE/FE ratio of slit width thresholds showed no correlation with interocular acuity differences, stereoacuity, or spatial contour integration deficits. CONCLUSIONS: Amblyopic children demonstrate significant deficits in temporal contour integration in AEs, which seem to be independent of spatial contour integration deficits. The severity of these temporal deficits increases with worse AE visual acuity. These findings suggest that amblyopia is associated with temporal deficits in visual integration, in addition to the well-documented spatial deficits, highlighting the need for a more comprehensive understanding of amblyopic visual processing.