HUMAN STRABISMUS - EVALUATION OF THE INTERHEMISPHERIC TRANSMISSION TIME AND HEMIRETINAL DIFFERENCES USING A REACTION-TIME-TASK

Experimentally induced strabismus in visually immature cats leads to a bnormal development of the posterior corpus callosum. This, in turn, s hould lead to abnormal interhemispheric integration of unilaterally pr esented visual information. To test whether strabismus produces defici ts in the human commissural visual system, the interhemispheric transm ission time (ITT) was compared in strabismic and normal subjects. Simp le unimanual reaction times (RT) were tested in 30 subjects in respons e to a lateralized target presented monocularly at 4 degrees and 35 de grees nasally and temporally from the fovea along the horizontal merid ian. This method was also used to examine the effect of strabismus on the central and peripheral portions of each hemiretina. The results sh owed that in strabismic subjects with or without amblyopia, the ITT di d not differ significantly from normals at both eccentricities. In non -amblyopic strabismic patients, RTs in the central and peripheral port ions of hemiretina were comparable to normals. However, a reduced spee d of response was found in the central visual field (4 degrees) in the amblyopic eye. Our results suggest that the ITT is normal in strabism ic subjects and that the longer RTs in the central portion of the nasa l and temporal hemiretina of the amblyopic eye may be associated with the severe amblyopic condition.