Investigations on Subjective and Objective Cyclorotatory Changes After Inferior Oblique Muscle Recession

Purpose. To determine subjective and objective cyclorotatory changes after surgery for oblique muscle disorders and to analyze the mechanisms of the well-known, long-term, postoperative, subjective cyclotorsional changes. Methods. Twenty-six patients underwent unilateral inferior oblique muscle recession for strabismus sursoadductorius (inferior oblique overfunction). Subjective and objective cyclodeviation were examined before surgery with and without diagnostic occlusion, as well as 1 day, 3 days, and 4 months after surgery. Subjective cyclodeviation was assessed by Harms' tangent scale. Objective cycloposition was measured by means of fundus cyclometry, a novel method using an infrared scanning laser ophthalmoscope. Results. Diagnostic occlusion did not lead to significant changes in either objective or subjective cyclodeviation. Preoperative objective excycloposition was nearly equally distributed between affected eyes and fellow eyes. Early surgically induced incyclorotatory effects were more pronounced objectively than subjectively. On long-term follow-up, a reduction in the incyclorotatory effect was found to be smaller subjectively than objectively. A significant difference between subjective and objective cycloposition was seen early after surgery, and a significant difference between subjective and objective cyclorotatory change was found immediately after surgery and on long-term follow-up. Conclusions. Long-term regression of the incyclorotatory effect after inferior oblique muscle recession was confirmed objectively and subjectively and can be explained as a cessation of preoperatively required binocular compensatory innervation. The authors conclude that the difference between objective and subjective regression is caused by sensory cyclofusion. Invest Ophthalmol Vis Sci. 1997;38:405-412. Subjective cyclodeviation, when tested on orthoptic examination, can differ from real objective cycloposition of the globe. 1 ' 2 It has been pointed out by Hessel 3 that the relation between sensory and motor cyclofusion in fusional cyclovergence is 3:1. In objective measurements of human cyclofusional response, Kertesz 4 found a fusion of disparities up to 5° without rotation of the globe. In Bielschowsky's head tilt test, sensory elements seemed to play an important role because pure motor compensatory counterrolling was found not to exceed 5 0 . 5 After surgery of the oblique muscles, torsional phenomena can be found that are still not From the Eye Hospital, Ludwig-Maximilians-University, Munich, Germany. Submitted for publication April 11, 1996; revised July 22, 1996; accepted September 30, 1996. Proprietary interest category: N. Reprint requests: Hermann Dieter Schiuorm, University Eye Hospital, MathUdmislrasse 8, 80336 Munich, Germany. clearly understood. As described by Herzau, 6 some persons complain of a postoperative subjective cyclorotatory overcorrection that disappears after a certain period of time. Others reveal a regression of the surgery-induced rotatory effect by recurrence of a certain amount of subjective cyclodeviation without having shown an overcorrection. Litde has been reported so far on objective cyclorotatory changes after oblique muscle surgery, and little is known about the relation between subjective and objective cyclorotatory changes. 7 ' 8 It was our aim to determine motor and sensory torsional elements in patients who underwent surgery of the oblique muscles to find an explanation for the above-mentioned phenomena. To that end, objective cycloposition and subjective cyclodeviation were measured in patients with oblique muscle disorders before and after surgery. In addition, we tried to quantify th