Light-stimulus-evoked blink reflex: methods, normal values, relation to other blink reflexes, and observations in multiple sclerosis

The blink reflex may be evoked by auditory click or light stimulation, the latter being constantly present in all healthy subjects. The latency and amplitude of the light-stimulus-evoked blink response (L-BR) is influenced by the light intensity, distance between the light stimulus and the eye, attention, and background facilitation. The L-BR was abnormal in 75% of definite and 61% of probable multiple sclerosis (MS) patients. When abnormal, the L-BR was more commonly absent than delayed. Optic nerve lesions could be identified by the pattern of abnormalities in the L-BR in some patients. The L-BR has proved to be a sensitive detector of abnormalities in the visual connections and, in combination with the Vth nerve stimulation-evoked blink response, a valuable detector of brainstem lesions.