Lateral spatial interaction in humans with abnormal visual experience

Foveal increment sensitivity has been determined using a small flashing test spot on a background with and without the presence of a steadily presented satellite light patch. The satellite was arranged at different distances from the test spot along vertical, horizontal, and oblique meridians. Normal subjects and those whose visual development was probably abnormal due to severe astigmatism (meridional amblyopes) were tested. Increment sensitivity for the test spot alone is considerably lower for the amblyopes than for normal subjects. The presence of the satellite patch depresses sensitivity for small separations and is alternately threshold-lowering and threshold-raising for larger separations. The influence of the satellite differs along the three meridians tested both in the normal and abnormal subjects.