Evoked potentials during recovery from blindness recorded serially from an infant and his normally sighted twin

Abstract

Visual evoked potentials (VEPs) elicited by diffuse field flashes were recorded from a behaviourally blind infant with his twin as control. The patient was tested at ages 4, 5, 6, 8, 10 and 15 months. In spite of his behavioural blindness, clear VEPs were recorded from the patient at age 4 months, although the wave form was monophasic as contrasted with the multiphasic wave form recorded from his twin at the same age. Latency to first deflection and to first peak were considerably longer for the patient. The patient's VEP wave form grew progressively more complex with age, paralleling recovery of useful vision. However, the VEP development anticipated behavioural recovery. It has been suggested that, because of the dissociation between VEPs and behavioural blindness, VEPs are not likely to be useful in establishing the diagnosis or prognosis in patients with cerebral blindness. However, the other side of this coin is that VEPs offer a means of testing the residual function of visual cortex in behaviourally blind patients.