In a previous paper,1 coactivity of extraocular muscles was studied during slow following movements with utilization of multiple channel electromyography. After this, a study of coactivity during following movements of the eye between tertiary positions was attempted. The same technique, previously described,2 was employed.
Cocontraction is defined as a simultaneous increased contraction of extraocular muscles which are normally antagonistic in their primary field of action. By movements between tertiary positions, we mean horizontal movements in upper and lower fields of gaze and vertical movements in right and left fields of gaze. We shall sometimes refer to the planes of such movements as tertiary planes.
The upper and lower fields of gaze were approximately 40 degrees above and below the horizontal. The right and left planes of gaze were approximately 50 degrees to either side of the primary position. Similarly, the amplitudes of the vertical movements were approximately 40
TAMLER E, JAMPOLSKY A, MARG E. Electromyographic Study of Following Movements of the Eye Between Tertiary Positions. AMA Arch Ophthalmol. 1959;62(5):804-809. doi:10.1001/archopht.1959.04220050066011