Evaluation of superior oblique weakening procedures

To evaluate two superior oblique weakening procedures, silicon expander (SE), and translational recession (TR), and their effects on correction of "A" pattern, vertical deviation in adduction and dorsoadduction, superior oblique overaction, and torsion.

In a prospective, institution-based study, 32 eyes of 16 patients having bilateral superior oblique overaction with significant "A" pattern (>10 prism diopters [delta]) were evaluated. The parameters studied were: change in "A" pattern; effect on vertical deviation in adduction and dorsoadduction; superior oblique overaction; and torsion. 95% reduction in "A" pattern with SE and 92% reduction with TR, indicating equal effect in collapse of "A" phenomenon (p=0.78). The extorsion produced by TR was more than that produced by SE (p=0.001).

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.