Horizontal misalignment in patients with unilateral superior oblique palsy

To determine the frequency and distribution of horizontal misalignment in patients with unilateral superior oblique palsy (SOP) and to determine the indications for combining horizontal with vertical strabismus surgery.

Patients included in the study had a vertical heterophoria or tropia that fit Parks three-step test for SOP and had no previous strabismus surgery or other ocular motility disturbance. Ocular motility and alignment were recorded. Outcomes between patients who had vertical surgery alone and those who had combined vertical and horizontal surgery were compared using the Student's t test.

Of 205 patients, 121 (59.0%) had a horizontal misalignment in addition to vertical strabismus. Ninety-six patients (46.8%) required strabismus surgery. Of these, 29 had 8 prism diopters (PD) or more horizontal deviation. Twenty-two had vertical combined with horizontal surgery (V+H group). Although their initial deviation was greater, these patients had better surgical outcomes than patients who had vertical surgery alone (V group). The V+H group had a final mean horizontal deviation of 2.18 PD compared with 6.85 PD in the V group (P < .01). Postoperative vertical alignment in the V+H group was also superior with a final mean vertical deviation of 3.7 versus 6.8 PD for the V group (P = .12).

These results indicate that horizontal misalignment is common in patients with SOP. Patients with 8 PD or more horizontal deviation benefited from surgical correction of the horizontal deviation in addition to the vertical surgery.