The efficacy of superior oblique split Z-tendon lengthening for superior oblique overaction

To evaluate the efficacy of superior oblique muscle split Z-tendon lengthening in the treatment of superior oblique muscle overaction with respect to normalization of superior oblique ductions and versions, reduction of A-pattern strabismus and correction of vertical deviations. In addition, to determine the incidence of complications of the procedure including overcorrection and the effect of the procedure on horizontal deviation.

A retrospective review was performed of 19 patients who underwent superior oblique muscle split Z-tendon lengthening for A-pattern strabismus or significant vertical deviation associated with superior oblique overaction between June 1980 and September 1999. Ten males and 9 females were included, ranging in age from 2 to 45 years (mean: 9 years). Patients underwent either a unilateral or bilateral superior oblique tendon lengthening based on the patient's clinical picture.

Ten of 11 patients (91%) who underwent unilateral tendon lengthening and 10 of 16 eyes (63%) that underwent bilateral superior oblique tendon had complete normalization of superior oblique action. Seven of 10 patients (70%) who underwent unilateral or bilateral tendon lengthening for a clinically significant A-pattern had the A-pattern completely eliminated or brought to a clinically insignificant level. All 8 patients who underwent a unilateral tendon lengthening for a clinically significant vertical deviation had reduction of the vertical deviation. There was no statistically significant effect of either the unilateral or bilateral procedure on horizontal deviation.

The superior oblique muscle split Z-tendon lengthening procedure is highly effective for normalization of superior oblique muscle function and reduction of A-pattern strabismus and vertical deviations associated with superior oblique muscle overaction.