Assessment and management of bilateral superior oblique pareses

31 patients with bilateral fourth nerve palsies are considered in this paper, 25 of the cases being traumatic in origin. Quantitative estimation of the torsional defect is carried out, using special synoptophore slides and a modification of the Lees' screen technique. Inability to prove the patient's retention of fusion in the presence of torsion is discussed. Although many of the traumatic cases had been rendered unconscious for varying periods of time up to several weeks by the initial injury with the known risk of losing fusion, sixteen out of seventeen patients undergoing surgery for their diplopia had postoperative evidence of binocular single vision.