[The optically evoked orbicularis oculi reflex: method, normal values, habituation]

The optically evoked orbicularis oculi-reflex (OOR) was investigated in 50 healthy volunteers by monocular and binocular stimulation, including eyes open and eyes closed. Latency, amplitude, and duration correlated considerably with the stimulus intensity. There was no significant correlation to the diameter of the pupil, provided that a constant supramaximal stimulus intensity was used. A statistically significant difference of the reflex parameters between males and females could not be demonstrated. In 12% of the healthy volunteers the optic orbicularis oculi-reflex could not be evoked. The mean age of these subjects was 53 years, and distinctly higher than the mean age of the whole collective (32,6 years). A slight, statistically not significant increase of latency and duration was found with increasing age. The optically evoked OOR even habituated rapidly during aperiodic stimulation. To prevent habituation interstimulus intervals of 30 s were necessary. During the 1 Hz-stimulation habituation was already observed at the third reflex response. The amplitudes decreased, and the latencies increased with increasing distance of the flash light. Measurable differences were observed even with distance changes of 10 cm. There was no significant influence of eye-closing on latency, amplitude and duration of the optic orbicularis oculi-reflex. The orbicularis oculi-reflex following a bright flash of light with a latency about 50 ms was differentiated from an eyelid-closure following a low flash intensity with a latency between 80 and 90 ms.