Electrophysiological evidence of cortical fusion in children with early-onset esotropia

PURPOSE. TO investigate sensory fusion responses in infants and children wi th early-onset esotropia to gain insights into the sequence of events that leads to strabismus. METHODS. Sensory fusion was tested by measuring visual evoked potential (VE P) responses to dynamic random dot correlograms (DRDCs) in a group of child ren (n = 23) with early-onset esotropia. Thirteen children were tested befo re surgical alignment, and 13 children were tested after surgical alignment (three children were tested before and after surgery). if the :angle of st rabismus was larger than 5 prism diopters, it n as corrected with Fresnel p risms (Fresnel Prism and Lens, Scottsdale, AZ). RESULTS. Five (38%) of the IS children who n ere tested before surgery show ed detectable VEP responses to correlogram stimuli compared with 11 (85%) o f the 13 children who were tested after surgical alignment. There n ere no significant statistical differences between VEP responses to DRDCs from the postsurgery group and VEP responses from an age-matched control group with normal binocular vision. CONCLUSIONS. The presence of cortical sensory fusion in children with early -onset esotropia suggests that a congenital defect of sensory fusion cannot be the root cause of esotropia in most children. The data suggest that sen sory fusion, when measured by VEP responses to DRDCs, is more robust than s tereopsis to abnormal binocular experience and support the notion that path ways processing correlated/anticorrelated stimuli may not completely overla p with pathways processing disparity information.