Analysis of Effect of Inferior Oblique Myectomy in Patients With Inferior Oblique Overaction

PURPOSE: To investigate the effect of inferior oblique (IO) myectomy by analyzing the correlation of the amount of inferior oblique overaction (IOOA), hypertropia and excyclotorsion before, between, and after IO myectomy in patients with various degrees of IOOA. METHODS: A total of 86 eyes from 59 patients with IOOA who underwent IO myectomy were enrolled in the present study. The correlation analysis was performed for the amount of IOOA, hypertropia and excyclotorsion before and after surgery, according to the preoperative amount of IOOA, hypertropia, and excyclotorsion. RESULTS: The IOOA decreased from +2.5 +/- 0.6 before surgery to -0.01 +/- 0.25 (p < 0.05) after surgery. The vertical deviation was 5.7 +/- 6.3 prism diopter (PD) and 2.3 +/- 5.2 PD (p < 0.05) postoperatively. The amount of cyclodeviation was 15.3 +/- 7.6degrees before surgery and 6.6 +/- 5.7degrees (p < 0.05) after surgery. The amount of surgical correction for IOOA and the hypertropia was significantly correlated with preoperative deviation (p < 0.05, p < 0.05). The amount of excyclotorsion before and after surgery was also positively correlated but was not statistically significant (p = 0.05). CONCLUSIONS: IO myectomy can correct any degree of IOOA, hypertropia, and related excyclotorsion.

The Effect of Myectomy on the Grading of Overaction of the Inferior Oblique Muscle

PURPOSE: This study assesses the surgical results of inferior oblique myectomy on the degree of overaction in patients with overaction greater than +2 of the inferior oblique muscle. METHODS: Seventy eyes of 54 patients underwent an inferior oblique myectomy and at least 6 months of follow-up. Patients with contracture of the superior rectus muscle or dissociated vertical deviation were excluded. The chief complaints, preoperative and postoperative degrees of overaction of the inferior oblique muscle, the angle of hypertropia, and head tilt were analyzed. RESULTS: Deviation of the eyeball (38.9%) and head tilt (25.9%) were the most common complaints. Overall, the success rate was 91.4%, and the likelihood of success decreased with increasing severity of overaction of the inferior oblique muscle. The angle of hypertropia reduced from 11.9 (Prism diopters, PD) preoperatively to 2.2PD postoperatively (p=0.000). Preoperative head tilting was seen in 20 patients (37%) and all saw postoperative improvement. CONCLUSIONS: Inferior oblique myectomy is effective in treating the overaction of the inferior oblique muscle without contracture of the superior rectus muscle or dissociated vertical deviation, especially in patients with greater than +2 overaction of the inferior oblique muscle.

Superior Oblique Palsy

I reviewed charts of 26 patients with superior oblique palsy who had been treated surgically. Diagnosis of superior oblique palsy was based on the Bielschowsky head tilt test(BHT) and overacting inferior oblique muscle. Four patients(15%) were diagnosed as having bilateral superior oblique palsy, and 22 patients(85%) were diagnosed as monocular superior oblique palsy. After myectomy of the overacting inferior oblique muscle, 6(27%) out of 22 patients initially diagnosed as monocular superior oblique palsy deveioped findings of superior oblique palsy on the opposite eye; these patients were considered as having masked bilateral superior oblique palsy. Among the 16 patients with unilateral superior oblique palsy, 11 patients(69%) showed negative BHT, 4 patients(25%) showed equivocal BHT and 1 patient(6%) still showed positive BET after surgery. Among the 14 patients who could be followed up for more than 3 months after the operation, 11 patients(79%) showed negative BHT, 2 patients(14.%) showed equivocal BHT, and 1 patient(7%) showed positive BHT. According to these results, the overacting inferior oblique muscle in superior oblique palsy plays a very important role in the elevation of the eye on ipsilateral head tilt, and the mechanism of the BHT classically described should be reconsidered. The primary operation was inferior oblique myectomy and secondary or tertiary operations were inferior oblique myectomy, marginal myotomy or superior rectus recession on the same or the other eye.