Activity balance of electromyograms in intermittent exodeviation

Abstract

Electromyograms of the four horizontal rectus muscles were recorded in intermittent exodeviation. Based on the activity balance between the medial and lateral rectus muscles during exodeviation, subjects were divided into the following types; in Type I, lateral rectus activity was more than that of the medial rectus; in Type II, activity was well balanced; and in Type III, medial rectus activity was more than that of the lateral rectus even during exodeviation of the eyes. The mean age and mean deviating angle increased in the order I, II, III. It was concluded that the electrical activity of the horizontal muscles in intermittent exodeviation varies widely and that active divergence is dominant in Type I, whereas compensatory active convergence is dominant in Types II and III.

Key Words:

• intermittent exotropia
• electromyography
• extraocular muscles
• divergence
• compensatory convergence