Mechanics of horizontal movement of the human eye.

1. The mechanics of the muscle-eyeball system of the human has been re-investigated by careful examination of the motion of the eye after it is mechanically adducted and released by means of a suction contact lens attached to it.2. Orbital stiffness during adduction is found to be about 1.25 g/deg which is near the value of 1.2 g/deg reported by Robinson (1965) for abduction. However, the results also show that the stiffness decreases to 0.65 g/deg after approximately 5 degrees of adduction.3. It is concluded that for horizontal motion the globe may be considered as being in series with an elastic component which has a stiffness of 9.0 g/deg. This series elastance, arising from the extraocular muscles, muscle tendons, and from other orbital tissue appears to increase in stiffness as muscle innervation increases.4. The experiments show that the muscle-eyeball system of the human is heavily damped which confirms the results of Robinson (1964).5. Evidence is presented which indicates that the extraocular muscles are dominant factors in horizontal eye motion.