A new test of contour integration deficits in patients with a history of disrupted binocular experience during visual development

Previous studies have suggested that the integration of orientation informa tion across space is impaired in amblyopia. We developed a method for quant ifying orientation-domain processing using a test format that is suitable f or clinical application. The test comprises a graded series of cards where each card includes a closed path (contour) of high contrast Gabor signals e mbedded in a random background of Gabor signals. Contour visibility in both normals and patients with histories of abnormal binocular vision depends j ointly on the spacing of elements on the contour as well as background elem ent density. Strabismic amblyopes show significant degradation of performan ce compared to normals. Small but significant tosses in sensitivity were al so observed in a group of non-amblyopic strabismus patients. Threshold meas urements made with contrast reducing diffusers indicated that the amblyopic loss is not due to the reduced contrast sensitivity of the amblyopic eye. An abnormal pattern of long-range connectivity between spatial filters or a loss of such connectivity appears to be the primary source of contour inte gration deficits in amblyopia and strabismus. (C) 2000 Elsevier Science Ltd . All rights reserved.