Monocular versus binocular vision in postural control.

OBJECTIVE In previous studies about the control of posture there have been controversial findings. Our aim was to examine the role of monocular and binocular vision in controlling posture in quiet stance. METHODS Twenty-eight normal subjects were tested. We used a force platform in measuring postural stability. In main experiment, postural stability was measured in four conditions: both eyes open (BEO), dominant eye open (DEO) non-dominant eye open (NDEO), and both eyes closed (BEC). In a further experiment, 11 subjects were tested in conditions where a vertical prism was placed in front of dominant eye. Prism was strong enough to cause diplopia. Our interest was to see, if diplopia affected the balance. RESULTS In main experiment, at level of group the body-sway in any of the three ocular (viewing) conditions did not differ from each other. At level of individuals, binocular vision was more effective on controlling posture in only half of subjects. In prism experiment, relative to normal binocular viewing the postural stability was modified in both prism conditions, but there was no difference between monocular and binocular viewing with prism. CONCLUSION In quiet stance and in subjects with perfect binocular vision and stereopsis, the benefit out of binocular viewing in postural stability is subject-dependent. At the level of group, monocular vision provides equally good postural stability as binocular vision.