Prognostic Value of Visual Evoked Responses in Childhood Amblyopia

Abstract

We assessed the possible clinical utility of pattern reversal visual evoked potentials in predicting the success of pleoptic treatment. Thirty amblyopic children –- 16 strabismic, 11 anisometropic and three of refractive type (in all cases the amblyopia was monocular) –- and ten children without amblyopia (control group) were examined by conventional psychometric methods. Visual evoked potentials (VEP) to pattern reversal stimulation were also recorded. The amblyopic group was treated with occlusion of the preferred eye for three to six months. Psychometric and VEP tests were repeated in 15 amblyopic children after the treatment. The pre-treatment VEP amplitude side-differences (between amblyopic and better fellow eye) were significant, with first positive wave, P1, being invariably lower on the amblyopic side. We correlated the side-differences in visual acuity with the corresponding side-differences in amplitude and latency of the P1 wave. In the former the correlation coefficient was r = 0.47 (p<0.01), and in the latter r = 0.65 (p<0.01). Latency was prolonged in the eyes with significantly reduced visual acuity in which the wave form was also typical for amblyopia. We then correlated the difference between pre- and post- treatment visual acuity of the amblyopic eye with the pre- and post-treatment difference in amplitude (correlation coeff. r-0.51 (p=0.05)) and latency of the P1 wave (correlation coeff. r=0.40 (p>0.05)). Finally, by correlating the pre- and post-treatment difference in visual acuity with the pretreatment P1 amplitude and latency (for the former, there was no regular interdependence, and for the latter r=-0.64 (p=0.01)), we tried to test our assumption that an alteration of VEP indicates poor visual rehabilitation of the amblyopic eye. Although the correlation was not unanimous, this study showed that VEP recording may still serve as an extra aid in predicting the therapeutic outcome in amblyopic children.