Superior oblique muscle palsy is one of the common causes of vertical strabismus in adults and children. Patients may apply with the complaint of vertical diplopia, or they have developed an abnormal head position to provide a single vision. Clinical findings associated with congenital superior oblique muscle palsy are torticollis and facial asymmetry (Fuller Face). Especially the presence of an abnormal head position is a strong indicator that the event is long-term. However, studies also question the relationship between facial asymmetry and superior oblique muscle palsy.9
It is known that most of the acquired superior oblique muscle palsy cases develop secondary to trauma. In the present study, there were predominantly congenital cases. In both of the acquired cases, the etiology is trauma. In traumatic cases, masked bilaterality is common. Therefore, in our study, we considered etiology was congenital if we could not find any other reason in patients without a history of trauma.
The head is generally in the direction of the shoulder, which is opposite to the affected eye, the chin is tilted down, and the face turns to the opposite side. Abnormal head position (92.3%) and diplopia (15.4%) were observed in the preoperative examination of the cases, and these features helped to diagnose superior oblique muscle palsy.
As determined in the present study, children often apply with the abnormal head position instead of diplopia. This is because the developing brain represses the central perception coming from a single eye in the presence of deviation. Older children with acquired superior oblique muscle palsy who have diplopia can express this symptom verbally. Adults may apply with the abnormal head position, vertical deviation, or with diplopia complaints developing due to excyclotorsion. When our cases were examined, diplopia was determined more frequently in adults in a similar way.10,11
Superior oblique muscle palsy may be bilateral. The degree of excyclotorsion is typically higher in bilateral cases than in unilateral cases.12 In masked bilateral cases, in cases in which mostly unilateral surgery is performed and the clinical picture is improved, similar problems arise on the opposite side after some time. In our case series, we did not encounter any problem in the early period in cases in which unilateral surgery had been applied.
Bhola et al. performed superior oblique muscle folding surgery in the isolated unilateral superior oblique muscle palsy. They stated that in acquired and congenital cases, in the postoperative period elevation limitation (Iatrogenic Brown Syndrome) was observed in adduction, but the limitation decreased over time. They reported that in acquired cases, while Iatrogenic Brown Syndrome was observed in the early postoperative period, the cases in both groups were asymptomatic.13 In the present study, Brown syndrome or the relapse of the clinical picture with the sutures getting loose was not observed in the postoperative early period. This situation supports our opinion, arguing that this surgical method may be appropriate to avoid complications.
Morris and Scott reported in their study that there was a 3.6 Prism Diopters improvement in the vertical deviation in the primary position after superior oblique muscle tucking surgery. They found the improvement amount to be 15.3 prism diopters also in the direction of eye movements, where the deviation was the highest.14 In our study, the deviation in the primary position, which was an average of 20.44 PD in the primary position, was lost in the early postoperative period. This result demonstrates that our surgical methods are effective in correcting vertical deviation.
Ludwig stated that the superior oblique muscle full tendon advancement method could be used in all kinds of superior oblique muscle weakness, including unilateral congenital or bilateral V patterned superior oblique muscle weakness and acquired superior oblique muscle palsy due to head trauma or vascular causes. The cause of congenital superior oblique muscle weakness was mostly observed to be tendon laxity or abnormal insertion. This method ensures that the insertion site of patients with this feature is changed and brought to a more anatomic position. Ludwig indicated that torsional diplopia could be observed postoperatively in some adult patients who had undergone unilateral superior oblique muscle full tendon advancement, but that this situation spontaneously regressed within 10–20 days.15 In the cases involved in our study, no symptoms related to torsional diplopia were observed in the postoperative examination.
Bata et al. stated that both in symmetric and asymmetric bilateral superior oblique muscle palsies, superior oblique muscle full tendon advancement surgery applied using an adjustable suture technique provides the independent control of the vertical and torsional components of the deviation. They indicated that a similar rate of excyclotorsion was observed in the postoperative period with the Harada-Ito procedure; therefore, more incyclotorsion correction was needed during torsional alignment. In their study, the postoperative adjustment was required in 80% of the patients, and they applied a correction with five mm regression or three mm advancement.16 In our series, an intraoperative adjustment was required only in one patient. The reason for this is the determination of the amount of advancement by the traction we applied after disinsertion during the surgery. This procedure seems to eliminate the need for post-surgical adjustment.
In one of our studies; we investigated the effectiveness and safety of disinsertion-distal myectomy and tucking of the inferior oblique muscle in patients with unilateral long-standing superior oblique muscle palsy and secondary inferior oblique muscle overaction. This technique was safe, simple, and effective. However, in cases with a high vertical deviation in the primary position, inferior oblique muscle weakening surgery alone is not sufficient and süperior oblique muscle strengthening surgery is required. According to Hatz et all isolated inferior oblique muscle weakening is an effective treatment option for superior oblique palsy up to 15 PD of vertical deviation in primary position. Two-muscle surgery should be reserved for patients with larger vertical deviations.17–18
In this study, the degrees of torsion, inferior oblique muscle hyperfunction, superior oblique muscle hypofunction, and the amount of vertical deviation in the primary position were examined preoperative and postoperative periods. The difference between them was found to be statistically significant (p < 0.01).
Surgical complications such as orbital cellulitis, endophthalmitis, scleral perforation, and Iatrogenic Brown Syndrome did not develop due to the low traumatic effect of our method.
The conducted studies demonstrate that the surgical method to be performed in superior oblique muscle palsy should be selected according to the condition of the patient and the experience of the surgeon.14,15,19,20 The short-term results of the methods we performed are satisfactory. However, studies with more cases and longer-term are needed.