Clinical characteristics according to the laterality of ocular torsion in unilateral superior oblique palsy

Background: To compare clinical characteristics according to the laterality of objective ocular torsion in patients with unilateral superior oblique palsy (SOP). Methods: This retrospective study included all patients with a diagnosis of unilateral SOP. They were classified into subgroups according to correspondence between the paretic eye and the extorted eye using fundus photography. Ocular alignment and muscle action were tested by the prism and alternate cover tests and 4-scale movement measure. Various clinical factors, including the amount of preoperative ocular torsion and change in ocular torsion postoperative, were compared between the accordance and disaccordance groups. Results: A total of 70 Asian patients (140 eyes) were included and underwent fundus photography preoperatively. Excyclotorsion in the paretic eye was defined as accordance (45 patients), excyclotorsion in the nonparetic eye was defined as disaccordance (25 patients). The presence of horizontal strabismus was detected in 28 (62%) patients in the accordance group and only 8 (32%) patients in the disaccordance group (p = 0.024). All horizontal strabismus observed in the accordance group involved exodeviation. The proportion of horizontal strabismus surgery was also significantly larger in the accordance group than the disaccordance group (p = 0.039). Among those patients, there were 26 who underwent fundus photography postoperatively. There was significant reduction in ocular excyclotorsion postoperatively in the accordance group (p = 0.001), but no significant reduction postoperatively in the disaccordance group (p = 0.270). There was no significant correlation between the amount of torsional reduction and the amount of vertical deviation reduction (p = 0.979). Conclusions: In cases of preoperative excyclotorsion in paretic eyes, careful consideration of combined horizontal misalignment which may require surgical correction is helpful to manage unilateral SOP.