Judgements of visual precedence by strabismics

Strabismus induced early in the life of cats results in disruption of the normal development of the posterior corpus callosum. In human strabismic amblyopic subjects a similar disruption in callosal development may cause poor interhemispheric integration of simple visual information. To examine this possibility judgements of visual target onset precedence were made for targets presented in bilateral and unilateral viewing conditions using a method of constants psychophysical procedure. In one condition, with targets presented in opposite visual fields requiring integration between the two hemispheres, the subjects having strabismic amblyopia had significantly larger just noticeable difference values (JNDs) than those found for the non-strabismic controls. In a second condition, with targets presented within a visual field requiring integration within only a single hemisphere, the JNDs for the two groups were not significantly different. The results suggest that strabismic amblyopes have poor integration of visual information between the cerebral hemispheres, and that this reflects disruptions in the development of the posterior corpus callosum.