Dichoptic luminance beat visual evoked potentials in the assessment of binocularity in children

Direct evidence of a distinct cortical binocular pathway has been provided by the production of nonlinear (difference) beats from dichoptic luminance stimulation in stereonormal adults and the absence or diminution of these beats in stereoblind subjects. We have investigated a clinically useful application of this technique in a pediatric population with potentially abnormal binocular vision. We recorded dichoptic luminance beat visual evoked potentials (VEPs) from 20 children (ages 7 months to 8 years) with abnormal binocular ability secondary to strabismus and/or amblyopia and compared this to a control group of 20 children with normal binocularity. Stereoblind children generated significantly lower dichoptic signal-to-noise ratios than stereonormal children (P < .001). Responses to monoptic multifrequency flicker were not significantly different between the two groups (P = .936). This dichoptic VEP can be performed quickly and easily on young children and gives a quantitative assessment of cortical binocularity that may not be determinable by standard clinical methods. This technique may also prove useful for the preoperative gradation of binocular potential and prediction of postoperative binocular fusion.