Vertical Rectus Surgery for Knapp Class II Superior Oblique Muscle Paresis

Abstract

Objective: To evaluate the efficacy of treating Knapp class II superior oblique muscle palsy with 7-mm nasal transposition of the ipsilateral inferior rectus muscle combined with recession of the contralateral inferior rectus muscle when the primary position hypertropia is 10 prism diopters (PD) or less.Method: A retrospective review of 8 consecutive patients with superior oblique muscle paresis who had nasal transposition of the inferior rectus muscle in the paretic eye and recession of the inferior rectus muscle in the nonparetic eye. Ocular motility, including objective and subjective torsion, were evaluated before and after surgery.Results: The mean (SD) preoperative hypertropia was 5 PD (1.5) and 13.1 (3.6) PD in the primary position and downgaze, respectively. After surgery the mean (SD) hypertropia was 1.25 (1.0) and 3.25 (1.3) PD in the primary position and downgaze, respectively. The mean (SD) subjective excyclotropia decreased from 6.6°(1.3°) preoperatively to 0.5°(0.9°) after surgery, and there was a mean (SD) objective decrease in the excyclotorsion of the paretic eye by 7.8°(1.4°). All patients were diplopic before surgery and asymptomatic after surgery.Conclusion: Treatment with 7-mm nasal transposition of the ipsilateral inferior rectus muscle combined with recession of the contralateral inferior rectus muscle can effectively treat Knapp class II superior oblique muscle palsy when the primary position hypertropia is 10 PD or less.

Outcomes of Harada-Ito surgery for acquired torsional diplopia

“…7,8 However, our data did not support this finding: the amount of torsion correction using Harada-Ito surgery alone versus in combination with vertical muscle surgery was similar. Most concomitant surgeries were performed to address a coexisting vertical deviation.…”

Does inferior oblique recession cause overcorrections in laterally incomitant small hypertropias due to superior oblique palsy?

“…20 Interestingly, Kushner reported eight patients diagnosed with SOP (Knapp class II) with central gaze hypertropia <10 PD who underwent contralateral IRR, none of whom had postoperative overcorrections during a follow-up period of a mean of 3.7 years. 21 This perhaps may be explained by the use of semiadjustable sutures 24 for some patients, or because of the small amount of patients in that study. 21 Kushner describes an alternative procedure for patients with SOP with small deviation hypertropia combining contralateral IRR and ipsilateral IR nasal transposition.…”

“…21 This perhaps may be explained by the use of semiadjustable sutures 24 for some patients, or because of the small amount of patients in that study. 21 Kushner describes an alternative procedure for patients with SOP with small deviation hypertropia combining contralateral IRR and ipsilateral IR nasal transposition. 25 This permits extra correction of excyclotropia.…”

“…In addition, IRR alone may not sufficiently address coexisting excyclotropia. 21 In this study, we evaluated effects of IOR in laterally incomitant hypertropia <10 PD in central gaze and clinically consistent with SOP. Our goal was to determine the incidence of postoperative overcorrections and the effect of surgery on lateral incomitance.…”

Predictive factors for corrective effect of inferior rectus recession for congenital superior oblique palsy

“…Knapp classified SOP into five patterns according to a grading system based on the positions of greatest vertical misalignment [1,2]. Knapp's classifications system is widely used for the selection of surgical procedure for SOP [3][4][5][6]; therefore, IRR is performed less frequently than other procedures. For example, in a report by von Noorden et al, IRR was selected to treat SOP in only 9% of cases, whereas ipsilateral inferior oblique recession (IOR) was used in 56% [3].…”