Anomalies of disparity detection in the human visual system.

1. Oculomotor and psychophysical depth responses were investigated in thirty individuals by use of briefly exposed disparities in the range from 0-6 to 4-6 degrees (1-8 centrads). 2. The results substantiate a previous finding which reported the common occurrence of specific types of stereoanomalies within a sample from the normal population. However, arguments are presented to suggest that these forms of stereoanomalies are limited to coarse stereopsis and spare mechanisms concerned with fine disparity, high resolution stereopsis. 3. A relatively high proportion of individuals were found to manifest deficiencies of vergence eye movement under these stimulus conditions. These vergence-anomalies are characterized by a marked reduction, or absence, of neither convergent or divergent eye movements to briefly exposed stimuli. 4. The vergence-anomaly is not detrimental under normal seeing conditions since it can be present in persons with adequate binocular vision and normal fine stereopsis. 5. The presence of vergence-anomaly was always associated with the occurrence of stereoanomaly; however, the converse was not true. 6. The results are taken as evidence to show how disparity information is organized prior to its influence upon the processes of coarse stereopsis and vergence initiation.