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Surgical Experiences With Two-Muscle Surgery for the Treatment of Intermittent Exotropia

https://doi.org/10.1016/j.jaapos.2005.11.015Get rights and content

Background: The surgical management of intermittent exotropia, or X(T), remains a challenge. Not only are some quoted success rates relatively low (40-83%), but the outcome is notoriously unpredictable with a tendency to exotropic drift over time. Methods: In this retrospective study, 118 patients who underwent either bilateral lateral rectus muscle recession (BLR) or unilateral medial rectus muscle resection and lateral rectus muscle recession (R&R) surgery during a 4-year period were reviewed. Surgical outcome between the 2 groups in addition to factors that influence outcome within groups were analyzed. Success was defined as an X(T) ≤ 10PD. Results: Sixty-four subjects underwent BLR, and 54 subjects underwent R&R surgery. Mean preoperative distant X(T) size was 38.7 ± 6.7 PD. Subjects who underwent R&R did significantly better at 1-year follow-up (success 74.2% vs. 42.2%) but showed significantly more exotropic drift over time (P = 0.01). Within both BLR and R&R groups, subjects with basic-type X(T) did worse than those with divergence-excess X(T) at 1-year follow-up. Consecutive esotropias, however, were more likely with R&R surgery and in those with divergence excess X(T). Preoperative strabismus control, distant X(T) size, and patient age at surgery did not significantly influence outcome. Conclusion: In many cases, selection of surgery type continues to depend on the surgeon’s preference, which is in turn influenced by his/her past experiences. The debate about which surgical type is best for different X(T) types continues.

Section snippets

Methods

All children younger than 16 years who underwent 2-muscle surgery for intermittent exotropia at the Singapore National Eye Centre (SNEC) between January 1992 and December 1995 were included in this study. Surgery was performed by 3 surgeons. Only those patients with X(T) with basic (B) or divergence excess (DE) X(T) and with distant strabismus size between 25 and 50 prism diopters (PD) were included.

Those children with constant exotropia or convergence-insufficiency X(T), past extraocular

Results

Using the hospital database, 203 patients were found to have had surgery for intermittent exotropia in the 4 years between January 1992 and December 1995. Of these, 2 had X(T) greater for near than distance. Thirty-one had 3-muscle surgery. An additional 45 patients had concurrent oblique muscle surgery. One had adjustable suture surgery. Six had inadequate follow-up. These patients were excluded from the study. The remaining 118 patients satisfied the entry requirements of this study.

Discussion

The surgical management of intermittent exotropia has been frustrating in its unpredictability. “Success rates” reported range from 40% to 83% (Table 5).1, 2, 3, 4, 5, 6, 7, 8, 9 Determining how much surgery to do itself is fraught with difficulty (Table 4). Using preoperative strabismus size measurement alone does not appear to provide predictable result. Many authors have looked at the various factors that may influence outcome (eg, type of surgery, age of surgery, amount of stereopsis, high

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