THE VALUE OF FLASH VISUAL-EVOKED POTENTIALS IN ALBINISM

In albinism, the majority of temporal retinal fibers serving the nasal visual field cross at the chiasm and project to the contralateral hemisphere. This misrouting is seen in hemispheric asymmetries present in the visual evoked potential (VEP). Misrouting of retinal fibers was also thought to occur in dissociated vertical deviation, Prader-Willi syndrome, and perhaps carrier states of albinism. However, recent literature is reaching the conclusion we have drawn in our laboratory: only albinism shows VEP hemispheric asymmetries that reverse when the other eye is stimulated. Use of different stimuli, recording conditions, and response criteria among investigators has created some confusion in differentiating what constitutes asymmetry. We conclude that use of a diffuse flash stimulus and a bipolar electrode derivation that compares differences between the left and right occipital hemispheres will clearly differentiate albinism from all other conditions, making it especially useful in a pediatric population.