The Effect of Unilateral Medial Rectus Resection for Recurrent Intermittent Exotropia

Dong Geun Park; Won Jae Kim; Myung Mi Kim

doi:10.3341/jkos.2014.55.11.1681

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Park, Kim, and Kim: The Effect of Unilateral Medial Rectus Resection for Recurrent Intermittent Exotropia

Original Article

J Korean Ophthalmol Soc 2014;55(11):1681-1686.

Published online: 2 September 2014

DOI: https://doi.org/10.3341/jkos.2014.55.11.1681

The Effect of Unilateral Medial Rectus Resection for Recurrent Intermittent Exotropia

Dong Geun Park, MD, Won Jae Kim, MD, Myung Mi Kim, MD, PhD

Department of Ophthalmology, Yeungnam University College of Medicine, Daegu, Korea

Address reprint requests to Myung Mi Kim, MD, PhD, Department of Ophthalmology, Yeungnam University Medical Center, #170 Hyeonchung-ro, Nam-gu, Daegu 705-802, Korea, Tel: 82-53-620-3441, Fax: 82-53-626-5936, E-mail: mmk@med.yu.ac.kr

Received 11 April 2014 Revised 11 June 2014 Accepted 7 October 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

The purpose of this study is to investigate the effect of unilateral medial rectus muscle resection (UMR) for the treatment of recurrent intermittent exotropia after bilateral lateral rectus muscle recession (BLR).

Methods

Medical records of 121 subjects who underwent UMR for the treatment of recurrent intermittent exotropia after BLR with more than six months of follow-up were reviewed. Patients were classified into two groups, the 4-mm group who underwent 4-mm UMR and the 5-mm group who underwent 5-mm UMR. Successful postoperative motor alignment was defined as within 10 prism diopters (PD) of exotropia and four PD of esotropia.

Results

The mean time interval between the primary surgery and recurrence was 13.55 ± 20.78 months (1-120 months). Average follow-up period after secondary surgery was 27.42 ± 15.98 months (6-48 months). Cumulative success rate at six months after UMR was 87.1% in the 4-mm group and 88.2% in the 5-mm group, respectively, and that at 24 months was 72.7% in the 4-mm group and 50.0% in the 5-mm group (p = 0.132). The average effect of resection was 4.87 ± 0.91 PD/mm in the 4-mm group and 4.73 ± 0.84 PD/mm in the 5-mm group (p = 0.374).

Conclusions

Because of recurrent intermittent exotropia, less time is required for surgery in UMR after BLR, and patients and parents are more likely to accept a secondary surgery because of single muscle surgery. Therefore, UMR may be an effective surgical method for patients with 16-30 PD of recurrent intermittent exotropia.

Keywords: Recurrent intermittent exotropia, Surgical outcome, Unilateral medial rectus resection

References

1. Zibrandtsen P, Rindziunski E, Gregersen E. Ten years follow-up of surgery for intermittent exotropia. Acta Ophthalmol (Copenh). 1986; 64:374–8.

2. Scott WE, Keech R, Mash AJ. The postoperative results and stability of exodeviations. Arch Ophthalmol. 1981; 99:1814–8.

3. Kim SJ, Choi DG. The clinical analysis after reoperation for recurrent intermittent exotropia. J Korean Ophthalmol Soc. 2007; 48:321–7.

4. Yang HK, Hwang JM. Bilateral vs unilateral medial rectus resection for recurrent exotropia after bilateral lateral rectus recession. Am J Ophthalmol. 2009; 148:459–65.

5. Kim SC, Kim MM. The efficacy of unilateral rectus resection in the reoperation of strabismus. J Korean Ophthalmol Soc. 2003; 44:904–10.

6. Yazdian Z, Ghiassi G. Re-recession of the lateral rectus muscles in patients with recurrent exotropia. J AAPOS. 2006; 10:164–7.

7. Suh YW, Seo IH, Cho YA, Kim SH. Analysis of the effects of medial rectus muscle resection for recurrent exotropia. Korean J Ophthalmol. 2011; 25:341–3.

8. Olitsky SE, Kelly C, Lee H, Nelson LB. Unilateral rectus resection in the treatment of undercorrected or recurrent strabismus. J Pediatr Ophthalmol Strabismus. 2001; 38:349–53.

9. Mims JL 3rd. Outcome of 5 mm resection of one medial rectus extraocular muscle for recurrent exotropia. Binocul Vis Strabismus Q. 2003; 18:143–50.

10. Chae SH, Chun BY, Kwon JY. The effect of unilateral medial rectus muscle resection in patients with recurrent exotropia. Korean J Ophthalmol. 2008; 22:174–7.

Figure 1.

Kaplan–Meier survival curve showing the cumulative probability of surgical success following a unilateral lateral rectus muscle resection procedure (p = 0.132, log rank test). UMR = unilateral medial rectus muscle resection.

Table 1.

Characteristics of patients

Factors	Values (n = 121)
Sex (M:F)	60:61
Age at onset (years)	2.13 ± 1.50
Age at diagnosis (years)	3.66 ± 2.11
Age at primary surgery (years)	5.49 ± 2.00
Amount of primary surgery with BLR
5 mm	35 (28.9%)
6 mm	86 (71.1%)
Time to recurrence^∗ after first surgery (months)	13.55 ± 20.78
Amount of secondary surgery with UMR
4 mm	70 (57.9%)
5 mm	51 (42.1%)
Average postoperative follow-up period after secondary surgery (months)	27.42 ± 15.98

Values are presented as mean ± SD unless otherwise indicated.

BLR = bilateral lateral rectus muscle recession; UMR = unilateral medial rectus muscle resection.

^∗ Recurrence was defined as exodeviation greater than 10 prism diopters.

Table 2.

Characteristics of patients in UMR 4-mm group and UMR 5-mm group

Factors	UMR 4 mm group	UMR 5 mm group	p-value
No	70 (57.9%)	51 (42.1%)
Sex (M:F)	34:36	26:25	0.794^†
Age at onset (years)	2.27 ± 1.37	1.94 ± 1.66	0.245^§
Age at diagnosis (years)	3.84 ± 2.01	3.41 ± 2.23	0.269^§
Family history of strabismus	5 (7.1)	7 (13.7)	0.232^†
Spherical equivalent refractive error (D)
Right eye	0.27 ± 0.92	0.35 ± 0.92	0.619^§
Left eye	0.33 ± 0.85	0.37 ± 0.90	0.772^§
Anisometropia (>1.5 D)	1 (1.4)	1 (2.0)	1.000^Π
Previous treatment of amblyopia	9 (12.9)	5 (9.8)	0.604^Π
Primary surgery
Age at primary surgery (years)	5.64 ± 2.02	5.29 ± 1.98	0.347^§
Preoperative deviation (PD)	23.21 ± 2.84	24.82 ± 2.70	0.002^§
Recession amount (5 mm:6 mm)	26:44	9:42	0.020^†
Overcorrection^∗ at postoperative 1 week	3 (4.3)	6 (11.8)	0.156^Π
Time to recurrence^† (months)	16.93 ± 23.92	8.92 ± 14.46	0.024^§
Period between primary and secondary surgery (months)	60.02 ± 34.25	50.94 ± 35.58	0.159^§
Secondary surgery
Age at secondary surgery (years)	6.35 ± 2.91	5.66 ± 2.73	0.190^§
Preoperative deviation (PD)	19.74 ± 1.43	25.10 ± 1.62	<0.001^§
Overcorrection^† at postoperative 1 week	5 (7.1)	2 (3.9)	0.698^Π
The average postoperative follow-up (months)	27.68 ± 16.06	27.05 ± 16.02	0.832^§
Time to recurrence^‡ after secondary surgery (months)	18.12 ± 13.45	17.56 ± 12.61	0.981^§

Values are presented as mean ± SD unless otherwise indicated.

UMR = unilateral medial rectus muscle resection; D = diopters; PD = prism diopters.

^∗ Overcorrection defined as more than 5 PD of esotropia/phoria;

^† Recurrence was defined as exodeviation greater than 10 PD;

^‡ Chi-square test;

^§ Independent t-test;

^Π Fisher exact test.

Table 3.

Deviation at preoperative day in UMR 4-mm group and UMR 5-mm group

PD	No. of patients
PD	UMR 4-mm group	UMR 5-mm group
<20	15	0
20	53	2
25	2	46
>30	0	3

UMR = unilateral medial rectus muscle resection; PD = prism diopters.

Table 4.

Comparisons of cumulative probability of surgical success rate in UMR 4-mm group and UMR 5- mm group

Success rate after secondary surgery	UMR 4-mm group	UMR 5-mm group
1 week	70/70 (100)	51/51 (100)
1 month	70/70 (100)	51/51 (100)
3 months	67/70 (95.7)	47/51 (92.2)
6 months	61/70 (87.1)	45/51 (88.2)
12 months	45/56 (80.4)	27/39 (69.2)
18 months	36/49 (73.5)	21/37 (56.8)
24 months	32/44 (72.7)	16/32 (50.0)

UMR = unilateral medial rectus muscle resection.

Table 5.

Surgical effects of medial rectus resection according to the amount of resection

Amount of resection (mm)	No. of patients	Mean corrected deviation (PD)	Mean effects per millimeter of MR resection (PD/mm)^∗
4	70	19.51 ± 3.65	4.87 ± 0.91
5	51	23.66 ± 4.20	4.73 ± 0.84

Values are presented as mean ± SD unless otherwise indicated.

PD = prism diopters; MR = medial rectus muscle.

^∗ Independent t-test: p = 0.374.

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