Figure Divergent and convergent ocular oscillations and attempts to upgaze and downgaze

Episodes of divergent (A) and convergent (B) ocular oscillations can be appreciated in primary gaze (the corneal light is displaced laterally from A to B). Note the elevation of the inferior eyelid crease (horizontal arrow, A to B), indicating contraction of the levator labii muscles, synchronous with the convergent ocular movements. Attempts to upgaze (C) and downgaze (D) are ineffective.