J Korean Ophthalmol Soc.  2019 Mar;60(3):268-275. 10.3341/jkos.2019.60.3.268.

Comparison of the Outcomes of Two- and Three-muscle Surgery in Exotropia over 45 Prism Diopters

• Kang KE
• Kim HC
• Shin HJ

• KMID: 2440455
• DOI: http://doi.org/10.3341/jkos.2019.60.3.268

Abstract

PURPOSE
We report the outcomes of two- or three-muscle surgery on patients with large-angle exotropia exceeding 45 prism diopters (PDs).
METHODS
We retrospectively analyzed data on 45 exotropia patients (> 45 PDs) who underwent two- or three-muscle surgery. We excluded patients with paralytic or restrictive strabismus, A- or V-pattern strabismus, a coexistent oblique dysfunction or nystagmus, and/or a history of prior extraocular muscle surgery. Only patients for whom at least 6 months of follow-up data were available were included. Successful surgery was defined as postoperative esotropia ≤ 5 PD, orthophoria, and exotropia ≤ 10 PD at the last visit.
RESULTS
We included 45 patients, of whom 22 and 23 underwent two- and three-muscle surgery, respectively. The mean postoperative deviations were 9.5 and 2.7 PD in the two- and three-muscle groups, respectively; the overall success rates were 54.55% (12/22) and 91.30% (21/23). Subgroup analyses revealed that the surgical success rate of two-muscle operations was 66.67% (12/18) in 45-55 PD patients and 0% (0/4) in ≥ 55 PD patients; the success rates of three-muscle operations were 100% (7/7) and 87.50% (14/16). The success rate did not differ significantly between those with postoperative deviations of 45-55 PD (p = 0.137), but did between those who underwent two- and three-muscle operations to treat postoperative deviations of ≥ 55 PD (p = 0.003).
CONCLUSIONS
Satisfactory results can be achieved via two-muscle surgery in patients with exotropia < 55 PD. However, for those with exotropia > 55 PD, three-muscle surgery is superior to two-muscle surgery. Therefore, large-angle exotropia is optimally treated via three-muscle surgery.

Keyword

Horizontal muscle surgery; Large angle exotropia; Strabismus muscle

MeSH Terms

Esotropia
Exotropia*
Follow-Up Studies
Humans
Retrospective Studies
Strabismus

Figure

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  Figure 1 The duration of follow up as measured by the survival analysis (*Kaplan-Meier method). The mean duration of success of the two muscle group and the three muscle group was 86.59 ± 11.94 months and 124.65 ± 5.70 months, respectively.

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  Figure 2 Success case according to the preoperative angle of deviation. The overall success rates were 63.6% (12/22) in two muscle groups and 91.3% (21/23) in three muscle groups. PD = prism diopters.

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  Figure 3 ROC curve. The maximum AUC is 0.84 and the sensitivity and specificity were 95.65% and 63.64% using a cut-off value of 50 prism diopters. ROC = receiver operating characteristics; AUC = area under the curve; CI = confidence interval.

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  Figure 4 The duration of follow up as measured by the survival analysis (*Kaplan-Meier method) in 50–65 prism diopters exotropia. The mean duration of success in the two muscle group and the three muscle group was 48.50 ± 23.15 months and 112.43 ± 9.96 months, respectively.

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