Surgical treatment of the A and V phenomena.

Our surgical treatment of the A and V phenomena consists of a systematic combination of oblique and horizontal muscle surgery. The oblique muscles are desagittalized: the plane of action of the muscle is displaced forwards so that its angle with the visual axis enlarges. The vertical action of the oblique muscle is thus reduced in favour of the torsional action. This desagittalization is always performed bilaterally and combined with a bilateral recession of a rectus muscle: the medial rectus muscles in cases of esotropia and the lateral rectus muscles in cases of exotropia. A real vertical deviation (RVD), if present, is treated by asymmetrical oblique muscle surgery or by the weakening of a vertical rectus muscle. In cases of under- or overcorrection a remaining diagonal and vertical deviation is carefully searched for and dealt with. In addition, a horizontal undercorrection is treated by placing a secondary loop on the already recessed medial rectus muscle, and a horizontal overcorrection is treated by weakening both lateral rectus muscles.