The immediate effect of bilateral superior obliuqe tenotomy on primary position horizontal binocular alignment

To evaluate the effect on primary position horizontal binocular alignment of superior oblique tenotomy for A-pattern exotropia with bilateral superior oblique overaction using new surgical and anesthesia techniques.

We performed intraoperatively adjustable horizontal strabismus surgery under topical anesthesia in 6 cases of A-pattern exotropia. After adjusting the horizontal deviation nearly to orthotropia in primary position, we measured the angle of horizontal deviation in up-, primary, and downgaze positions. This was followed by bilateral superior oblique tenotomy and remeasurement of the horizontal deviation in the same 3 positions. Postoperatively we remeasured the deviation at one day, one month and three months.

There was no immediate change in the horizontal deviation in primary position in 2 of the 6 patients, and 3-8 delta of immediate esotropic shift in 4 of the 6 patients (average 3.3 delta) after bilateral superior oblique tenotomy. At 3 months postop' the small esotropia noted at the immediate postop' measurement became orthotropic. There was a tendency of increased exotropic shift or becoming exotropic in those patients with slight exotropia or orthotropia at the immediate postop' measurement. But these shifts were minimal.

When combined surgery of superior oblique and horizontal muscle is planned for A-pattern exotropia, the effect of bilateral superior oblique tenotomy on the primary position horizontal binocular alignment can be disregarded.