Conjugacy of eyelid movements in vertical eye saccades.

PURPOSE To examine the conjugacy of lid saccades in normal subjects. METHODS Saccades of both upper eyelids were recorded simultaneously by means of small, lightweight, magnetic search coils, fixed on each lid. Subjects then made vertical eye saccades between fixed targets. The associated eye saccades were recorded simultaneously by means of magnetic search coils. The authors further examined whether the position of the lid coils affected the recordings. RESULTS Lid saccades were not as conjugate as their associated eye saccades. Nonconjugacy of lid saccades averaged approximately 8% of the target amplitude, irrespective of saccadic direction. By contrast, nonconjugacy of the associated eye saccades averaged approximately 1% of the target amplitude. Coil position significantly (P < 0.05) affected the recordings. CONCLUSIONS Lid saccades are not as conjugate as their associated eye saccades. Coil position is critical for the recordings of lid saccades.