Comparing Two Inferior Oblique Weakening Procedures: Disinsertion versus Myectomy

Abstract

Purpose: To compare two methods for treating inferior oblique overaction (IOOA): disinsertion versus myectomy of the muscle.
 Methods: In this prospective interventional case series, patients were randomly assigned to undergo either IO myectomy or disinsertion. The changes in vertical and horizontal deviations following these two surgical procedures were evaluated. The postoperative IO function of grade 0 or +1 and the fundus extorsion of grade 0 or +1 was considered as the successful outcome.
 Results: Thirty-six patients (50 eyes) with a mean age of 12.67 ± 4.05 years were included. In the myectomy group, the mean preoperative hyperdeviation in adduction was 29.5 ± 9.32 prism diopter (PD), which decreased to 9.15 ± 7.86 PD after surgery (P = 0.001). In the disinsertion group, these measurements were 32.73 ± 12.42 and 12.65 ± 9.34 PD before and after the surgery, respectively (P = 0.001). The success rate of surgery based on the IOOA grading was 87.4% and 92.3% in the myectomy and disinsertion groups, respectively (P = 0.780). The successful correction rate of abnormal fundus torsion was 91.6% in the myectomy and 88.4% in the disinsertion group (P = 0.821). In comparison, 48% of the cases in the myectomy group and 50% in the disinsertion group were within the normal range of torsional position postoperatively (P = 0.786). There was no statistically significant difference in terms of changes in the horizontal or vertical deviations, V-pattern, and dissociated vertical deviation between the two groups.
 Conclusion: Both surgical techniques seem to be effective for treatment of inferior oblique muscle overaction.

Effect of bilateral inferior oblique partial myectomy on V pattern exotropia with inferior oblique overaction

“…3) A severe upshoot of the adducting eye was considered grade 3 overaction. 4) An extremely severe upshoot of the adducting eye was regarded as grade 4 overaction [ 15 ].…”

Comparative Study between Inferior Oblique Muscle Standard Anteriorization versus Myectomy in Primary Inferior Oblique Over Action

“…Identification of the inferior temporal vortex vein should be done in every case to avoid damaging it during the procedure. Subconjunctival hemorrhage and lower lid edema were early post-operative complications encountered in 2 cases in the myectomy group immediately postoperatively and resolved completely at the end of the 3 rd week [16] .…”

Surgical Outcome of Inferior Oblique Myectomy versus Recession–Anteriorization in the Treatment of Inferior Oblique Overaction

“…Although many studies have been conducted to compare IOM and IORA, it is still inconclusive which procedure is better. 2 , 15 , 18 Some studies have suggested IOM over IORA for the treatment of bilateral symmetrical SO palsy with bilateral IOOA because it is simpler and more effective. 19 , 20 Other studies found IORA to be superior in the correction of IOOA and hypertropia in the primary position and other gaze positions.…”

“…Inferior oblique overaction, IOOA is a cause of overelevation in adduction 1 which is usually associated with horizontal deviation, as observed in 70% of patients with esotropia, ET and 30% of patients with exotropia, XT. 2 Overaction can be categorized by etiology into primary and secondary IOOA. Primary IOOA has no identifiable cause and is commonly found in patients with infantile ET, which is associated with disruption of binocular vision development.…”