Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Surgical outcome in superior oblique muscle palsy

S. Zıylan, A. Yigit, Ö. Yabas, D. Serin, S. Hoca & I. Daruga

Sisli Etfal Education and Research Hospital, Istanbul, Turkey

ABSTRACT: 25 patients who underwent surgical correction for unilateral superior oblique palsy were enrolled in the study. Inferior oblique recession was performed to treat the cases with hypertropia of 15 prism diopters or less. In cases with more than 15 prism diopters hypertropia, inferior oblique recession was combined with contralateral inferior rectus recession. Cases with marked laxity of the superior oblique muscle were treated with superior oblique tendon tuck. A patient was considered to have successful outcome if the abnormal head posture and diplopia were relieved and the postoperative hyperdeviation was 5 prism diopters or less in primary position and 10 prism diopters or less in oblique gaze positions. Our overall success rate was %84. In the treatment of superior oblique palsy favorable results can be achieved with careful clinical assessment and appropriate surgical intervention.

1INTRODUCTION

Superior oblique muscle palsy is the most common form of paralytic strabismus. Congenital superior oblique palsy is encountered more often than the acquired form. The etiologic factors in the congenital form are laxity, abnormal insertion or the absence of the superior oblique tendon. Trauma, intracranial pathologies and microvascular disorders can lead to acquired paralysis. Abnormal head posture, facial asymmetry, high vertical fusion amplitudes are seen more frequently in patients with congenital palsy. Complaints of image tilt, excyclotropia and diplopia are characteristics of acquired superior oblique palsy. (Dale 1982, Von Noorden 1996).

There are various surgical techniques and different results in the treatment of superior oblique palsy. In the current study we reviewed 25 cases with unilateral superior oblique palsy and evaluated the outcome of their surgical treatment.

2METHODS

The subjects of this study consisted of 25 patients with unilateral superior oblique palsy followed in the ophthalmology clinic of Sisli Etfal Hospital between 1997 and 2003. Each patient underwent complete ophthalmologic examination. Abnormal head posture and facial asymmetry was noted if present. The angle of deviation was measured with the prism and alternate cover test in 9 diagnostic gaze positions. Bielschowsky head tilt test was considered positive if the hyper deviation on the palsied side was at least greater by 5 prism diopters. Binocular status was assessed with the Titmus and Worth 4 dot test. Torsion was measured with the double Maddox rod. Extraocular muscle functions on versions were graded from 0 to 4 for under actions and 0 to 4 for over actions.

The diagnosis of superior oblique palsy was based on the Parks’ 3 step test. Surgical intervention was planned according to the classification of Knapp and Moore (Knapp 1971, Knapp & Moore 1976). Cases with primary position hypertropia of 15 prism diopters or less underwent ipsilateral inferior oblique recession and those with primary position hypertropia of more than 15 prism diopters underwent ipsilateral inferior oblique recession and contralateral inferior rectus

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recession. Patients with advanced laxity of the superior oblique muscle on the forced duction test were treated with superior oblique tendon tuck.

A patient was considered to have successful outcome if the abnormal head posture and diplopia were relieved and the postoperative hyper deviation was 5 prism diopters or less in primary position and 10 prism diopters or less in oblique gaze positions.

3RESULTS

15 female and 10 male patients with an average age of 13, 5 years (range: 4–40 years) were enrolled in the study. The average follow up time was 18 months (range: 4–32 months). 18 patients had their palsy from birth or early infancy. In 3 cases the palsy was considered traumatic in origin and in 4 cases the cause was unknown.

The presenting symptoms included abnormal head posture (n: 3), diplopia (n: 3) and cosmetically unacceptable ocular alignment (n: 19). Facial asymmetry was present in 10 patients.

22 patients had some degree of binocularity. 15 of the 22 had stereoacuity ranging from 3000 to 40 arc/sec and the remaining 7 had peripheral fusion. Extorsion could be measured in 19 patients. The average amount of excyclotorsion was 3.5° (range: 0–8°). All of the patients had overaction of the ipsilateral inferior oblique muscle varying from 1 to 4.

The average distance hyperdeviation in primary position was 17.6 prism diopters (range: 10–30 prism diopters). Types of palsy and the preoperative hyperdeviations in primary position is shown in Table 1. 9 patients had an associated esodeviation of 8 prism diopters or more, and 4 had an associated exodeviation of 12 prism diopters or more. 7 of these 13 patients underwent concomitant horizontal rectus surgery.

11 patients with type I palsy and primary position hyperdeviation of 15 prism diopters or less underwent solitary inferior oblique recession. Among the patients with 16 to 30 prism diopters of primary position hypertropia, 8 with type III palsy and 4 with type IV palsy underwent inferior oblique recession and contralateral inferior rectus recession. Two patients with type II palsy had superior oblique tendon tuck.

Our mean correction of hyperdeviation in all positions of gaze was 11.1 prism diopters with inferior oblique recession, 19.5 prism diopters with combined inferior oblique and contralateral inferior rectus recession. With superior oblique tendon tuck 16 prism diopters of hypertropia were corrected in the field of the palsied muscle. Our overall success rate was 84%.

Table 1. Types of palsy.

Table 2. Postoperative results.

Average hypertropia

Prism diopters

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Residual primary position hypertropia more than 5 prism diopters was present in 4 patients at the end of the follow up period. 2 of these patients still had abnormal head posture. A mild Brown syndrome with 1 limitation developed in one of the patients who had superior oblique tendon tuck.

4DISCUSSION

In the treatment of superior oblique palsy choice of surgical technique varies among different authors. Knapp and Moore classified superior oblique palsy according to the angle of deviations in primary and oblique gaze positions and recommended surgical guidelines (Knapp 1971, Knapp

&Moore 1976). This classification provides appropriate surgical orientation in most cases.

In superior oblique muscle palsy, the response to surgery is strongly related to the amount of

preoperative deviation. Weakening of the overacting inferior oblique muscle is generally the preferred operation for treatment of most patients with unilateral superior oblique palsy (Dyer & Duke 1976, Helveston & Haldi 1976, Toosi & Von Noorden 1979, Katz 1984). However, patients with large angle deviations often require two muscle operations.

Toosi & Von Noorden reported favorable results with isolated inferior oblique myectomy in their series of unilateral superior oblique palsy with small angle deviations. The mean preoperative deviation in primary position was 15.1 prism diopters in this series (Toosi & Von Noorden 1979). Farvardin & Nazarpoor reported an average reduction of 14.52 prism diopters with anterior transposition of the inferior oblique muscle (Farvardin & Nazarpoor 2002). Flanders & Draper preferred to perform disinsertion or myectomy in type I palsy with a primary position hypertropia of 15 prism diopters or less (Flanders & Draper 1990). Our choice of surgery was similar for small angle superior oblique palsy. We performed inferior oblique recession in cases with 15 prism diopters or less hypertropia in primary position, and our success rate was 82% with this technique.

Many authors recommend two muscle operations for patients with large angle vertical deviations as single muscle operations may cause undercorrections (Jampolsky 1971, Mittelman & Folk 1976, Saunders 1986, Flanders & Draper 1990). In this study we combined inferior oblique muscle recession with contralateral inferior rectus muscle recession for more than 15 prism diopters of primary position hypertropia in type III and IV palsy. With this surgical approach our success rate was 83%. Lower eyelid deformity is one of the complications of inferior rectus recession. To avoid this adverse event, we limited the amount of recession to 4 mm. None of our patients showed lower eyelid deformity. In type III palsy another choice of surgery is combining ipsilateral superior oblique tendon tuck with inferior oblique muscle recession. Saunders reported favorable results with this technique (Saunders 1986).

Knapp recommends superior oblique tendon tuck for superior oblique palsy in which the angle of deviation is greater in the field of the paretic muscle (Knapp 1971, Knapp & Moore 1976). This technique can lead to iatrogenic Brown syndrome. In the retrospective study of Simons et al., postoperative Brown syndrome rate was 60% with superior oblique tendon tuck (Simons et al. 1998). Helveston et al. reported a rate of 17% for mild Brown syndrome following and resection (Helveston et al. 1996). In our study a mild Brown syndrome of 1 limitation occurred in one of the two patients that underwent superior oblique tendon tuck.

5CONCLUSION

In our study we achieved satisfactory results with isolated inferior oblique muscle recession in the treatment of unilateral superior oblique palsy with primary position hypertropia of 15 prism diopters or less. For larger angle deviations, combining contralateral inferior rectus recession is with inferior oblique recession is an effective option. Superior oblique tendon tuck is also a satisfactory method for cases with laxity of the superior oblique tendon.

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With careful clinical assesment, superior oblique palsy can be diagnosed without difficulty. If the deviation patterns are carefully determined, appropriate surgery can be performed with a high degree of success.

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