Outcomes of Asymmetric Primary Inferior Oblique Muscle Overaction Managed by Bilateral Myectomy and Tucking of Proximal Muscle End: A Cohort Study

Efficacy of inferior oblique belly transposition combined with inferior oblique recession for asymmetric inferior oblique overaction

OBJECTIVE

To evaluate the efficacy of inferior oblique belly transposition (IOBT) combined with inferior oblique (IO) recession in treating bilateral asymmetric inferior oblique overaction (IOOA).

METHODS

A retrospective review. The data of 14 patients who underwent IOBT on the mild side of IOOA and IO recession on the severe side for bilateral asymmetric IOOA were analyzed retrospectively. The main surgical results including the correction of IOOA, hypertropia, horizontal deviation, V pattern, and fovea-disc angle (FDA) were observed.

RESULTS

The IOBT corrected the preoperative grade (+1.86 ± 0.53) of the mild-side IOOA to a postoperative grade (+0.07 ± 0.27; p < 0.001), and the severe-side IOOA was corrected from a grade of +3.14 ± 0.53 to a postoperative grade of +0.14 ± 0.36 by the IO recession (p < 0.001). The vertical deviation at distance in the primary position was decreased from 8.43 ± 4.05 PD preoperatively to 1.21 ± 1.48 PD postoperatively (p < 0.001). The mean V pattern was 25.00 ± 11.62 PD preoperatively and 3.18 ± 2.18 PD postoperatively (p < 0.001). The mean preoperative FDA on the side where IOBT was performed was -10.47 ± 5.85 degrees, and the postoperative FDA was -7.82 ± 6.42 degrees (p = 0.023). The mean FDA on the side with IO recession was -11.05 ± 5.14 degrees before surgery and -6.09 ± 4.52 degrees after surgery (p = 0.001). The overall success rate was 71.4% (10 of 14).

CONCLUSIONS

IOBT combined with IO recession is effective and safe in eliminating hypertropia, V pattern, and extorsion with bilateral asymmetric IOOA.

[Surgical treatment of vertical strabismus. Part 1. Classification and diagnostics]

Vertical strabismus caused by hyperfunction of the inferior oblique muscle is a common oculomotor disorder. It is found in one third of all patients with strabismus, and in 70% of cases it is combined with esotropia. To date, there is no single approach to determining the degree of hyperfunction of the inferior oblique muscle, and the most common classifications are very subjective and inaccurate. Thus, in connection with the need to understand the severity of the disease, as well as to determine the tactics of treatment and prognosis of the surgical outcomes, it is necessary to standartize the classification of this pathology. The mechanism of action of the inferior oblique muscles of the eye is very complex and depends on the position of the eyeball at the time of their contraction. In addition to horizontal and vertical movements, they provide torsional movement. Any impairment of these muscles leads to the development of not only vertical strabismus, but excyclotropia that reduces the effectiveness of strabismus treatment. To identify all the symptoms associated with hyperfunction of the inferior oblique muscle, taking into account the peculiarities of its triple action, it is necessary to conduct a thorough diagnostic study.