Evaluation of superior oblique weakening procedures

Purpose: To evaluate two superior oblique weakening procedures, silicon exp ander (SE), and translational recession (TR), and their effects on correcti on of "A" pattern, vertical deviation in adduction and dorsoadduction, supe rior oblique overaction, and torsion. Method: In a prospective, institution-based study, 32 eyes of 16 patients h aving bilateral superior oblique overaction with significant "A" pattern (> 10 prism diopters [Delta]) were evaluated. The parameters studied were: cha nge in "A" pattern; effect on vertical deviation in adduction and dorsoaddu ction; superior oblique overaction; and torsion. Results: The index of surgical effect (ISE), showed 95% reduction in "A" pa ttern with SE and 92% reduction with TR, indicating equal effect in collaps e of "A" phenomenon (p=0.78). The extorsion produced by TR was more than th at produced by SE (p=0.001). Conclusions: Both the SE and TR procedures offered controlled weakening of the superior oblique and caused a 95% and 92% reduction in the "A" pattern. The latter procedure caused a marked extorsional change, three times that which resulted from SE. Both the procedures leave residual superior oblique overaction.