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.

Measurement of subjective and objective cyclodeviation in oblique eye muscle disorders.

Surgically induced changes of eye torsion often show a subjective over-effect which resolves later on. Hence the authors initiated a prospective study with the purpose of analyzing motoric and sensoric elements in postoperative rotational changes by comparing subjective and objective cycloduction. Fundus cyclometry, a new method for measurement of objective cycloduction, is introduced. An image of the posterior pole is obtained by an infrared Scanning Laser Ophthalmoscope without pupil dilatation and is transferred to a computer system by which nature and amount of objective cycloduction is calculated. Four patients who underwent surgery for oblique eye muscle disorders are presented. Objective torsional changes were slightly higher than subjective changes. Postoperative reduction of torsional changes was noted subjectively and objectively in all cases. For statistical reasons further investigations on a great number of patients are needed to interpret the postoperative changes in terms of motoric and sensoric cyclofusion.