Depth discrimination oflarge disparities (2 degrees) presented in the peripheral visual fields was investigated for ten stereoanomalous observers who could not discriminate among three types of disparity (crossed, uncrossed, and zero) presented symmetrically about the fixation point in the mid-sagittal plane, i.e., midline stereopsis.Seven out of the ten could detect all or some types of disparity and the other three could not detect any type of disparity.The result is not compatible with Richards' suggestion that for midline stereopsis to be normal, stereopsis in both hemispheres also has to be normal.Rather, the fact suggests that disparity detectors in each hemispheres are independent from disparity detectors correlating disparity information from both hemispheres.The trouble with the interhemispheric link which is requisite for correlating disparity information from both hemispheres is thought as one of the causes of stereoanomaly in midline stereopsis.
Shimono et al. (Sat,) studied this question.