Visual electrical evoked potentials: evaluation of ocular injuries.

Clinical neurophysiologists may be asked to participate in the evaluation of patients with injured eyes. We describe a method for eliciting evoked potentials of cerebral origin using electrical pulse stimuli delivered to the globe of the eye through a contact lens electrode mounted on the cornea. These visual electrical evoked potentials (VEEPs) are contrasted with conventional flash visual evoked potentials in normal subjects and in 19 eyes of 17 patients with severe ocular damage, mostly recent trauma. The findings suggest that the site of transcorneal electrical excitation is not the photoreceptors, but more likely one of the nerve cell layers of the retina. VEEP recordings offer a way to circumvent the opacification of the ocular media by blood, which may otherwise hamper the evaluation of retinal function in the injured eye. Preserved VEEP response does not necessarily predict the capacity to recover visual function. Absent VEEP response is an unfavorable prognostic sign, which may be considered in arriving at a decision about enucleation.