Twenty-nine patients have undergone major subtotal orbital translocation surgery between 1976 and 1980. Extra-ocular muscle function has been studied before and after orbital surgery. Medial orbital translocation, like sagittal orbital translocation, produces a decrease of exotropia; sometimes there is no change which proves the importance of well-established binocular vision. Orbital osteotomy in the three planes can produce a modification of the primary position of a vertical imbalance but it has no action on the vertical movements. The ophthalmologist can predict the post-operative result when he knows what type of ocular abnormality exists and what type of orbital surgery will be performed. He can also discuss the timing of strabismus surgery.