Purpose
To evaluate the long-term results of 2-muscle surgery in children with primary large-angle exotropia, comparing 10 mm bilateral lateral rectus recession (BLR) with unilateral lateral rectus recession-medial rectus resection (recess/resect).
Design
Retrospective case series.
Methods
Eighty-six children with exotropia of ≥40 prism diopters (PD), who underwent the 10 mm BLR (BLR group) or the unilateral recess/resect procedure (RR group) based on the largest angle measured at distance or near were included. Patients were followed-up for more than 2 years. Final successful alignment rates, stereopsis, and factors related to recurrence and overcorrection were evaluated.
Results
At the final examination, 29 (60.4%) of 48 patients in the BLR group achieved successful alignment; 16 (33.3%) had recurrence, and 3 (6.3%) had overcorrection. In the RR group, 26 of 38 patients (68.4%) were successfully aligned, 10 (26.3%) had recurrence, and 2 (5.3%) had overcorrection. Successful alignment and recurrence rates were not significantly different in the groups ( P = .371 and .640, respectively). The overcorrection rate was significantly higher in the RR group ( P = .014) until 2 years after surgery, but this difference was not significant afterward ( P = 1.000). In patients with an exodeviation of ≥45 PD, the recess/resect procedure showed higher successful alignment rates at the final examination ( P = .006).
Conclusions
The long-term successful alignment rate of 2-muscle surgery in children with primary large-angle exotropia was 64%, and the overall surgical outcomes were comparable between the BLR and RR groups. However, in patients with exotropia of ≥45 PD, the unilateral recess/resect procedure resulted in more favorable long-term outcomes.
In patients with large-angle exotropia, 2-muscle surgery can save other rectus muscles in case of reoperation and requires a shorter operation time. The success rate of 2-muscle surgery has been reported to be between 33% and 83%, but most of these studies have included patients with a wide range of exodeviation. In addition, the surgical table for large-angle exotropia of ≥40 prism diopters (PD) has not been well established.
Several studies have been performed in patients with large angles of exodeviation, but they had diverse inclusion criteria; various causes of exotropia (eg, consecutive, sensory, or paralytic strabismus); differing criteria of successful postoperative alignment; and were focused primarily on adults. In children with primary large-angle exotropia, the decision to perform optimal surgery is still debated. Additionally, previously reported alignment survival analyses after surgery for large-angle exotropia have compared surgical procedures involving various numbers of rectus muscles.
In this study, we evaluated the long-term outcomes of single-staged 2-muscle surgery in children with primary large-angle exotropia who were followed-up for more than 2 years. We compared the long-term successful alignment, recurrence and overcorrection rates after maximum bilateral lateral rectus recession (BLR) with unilateral lateral rectus recession and medial rectus resection (recess/resect; RR) procedure in these patients.
Methods
A retrospective review of medical records was performed for 121 consecutive children aged 3 to 17 years who underwent surgery for large-angle exotropia of ≥40 PD by 1 surgeon (J-MH) between 2007 and 2009. The minimum required follow-up period after surgery was 24 months, except for patients who required reoperation for overcorrection or recurrence within 24 months after the first surgery. Patients with congenital anomalies, neurologic disorders, paralytic or restrictive strabismus, history of previous strabismus surgery, moderate to severe amblyopia, coexisting ocular diseases other than strabismus, or infantile exotropia were excluded. Patients with dissociated vertical deviation, A or V patterns, or oblique muscle overactions not requiring surgery were included. This study adhered to the Declaration of Helsinki, and the protocol was approved by the Institutional Review Board of Seoul National University Bundang Hospital.
Preoperative Ophthalmologic Examination
All patients underwent complete preoperative ophthalmologic examinations. We performed prism and alternate cover testing with accommodative targets for fixation at one third and 6 m. An additional near measurement was obtained after 1 hour of monocular occlusion of the habitually deviating eye, and another postocclusion near measurement was obtained with an additional +3.00 diopters (D) sphere over each eye prior to allow the patient to regain binocular fusion. The presence of fixation dominance was determined with alternate cover testing. In cases of constant deviation, the invariably fixating eye was regarded as the dominant eye. In cases of intermittent exotropia, the eye to which fixation was invariably limited was regarded as the dominant eye when exhibiting a manifest exodeviation.
Refractive errors were determined by cycloplegic refraction and analyzed as spherical equivalent values. For patients with myopia of ≤−1.00 D, spectacles with full cycloplegic refraction were prescribed. In patients with hyperopia >+3.00 D, spectacles with approximately +1.00 to +1.50 D less than the full cycloplegic refraction were given. Also, spectacles were prescribed for patients with anisometropia, defined as a spherical or cylindrical difference of >1.50 D between both eyes. Amblyopia was defined as a difference of 2 lines or more between monocular visual acuities and only mild amblyopia with a difference of 2 lines were included. Lateral incomitance was defined as ≥5 PD change in the lateral gaze from the primary position. An A pattern was defined as an increase of 10 PD or more of exodeviation at downgaze compared with upgaze, and a V pattern was defined as an increase of 15 PD or more of exodeviation at upgaze compared with downgaze. Sensory status was evaluated with the Randot stereoacuity test at distance and near. Stereopsis of ≤100 seconds of arc was defined as good.
Intraoperative Procedures
All surgeries were performed under general anesthesia by 1 surgeon (J-MH). Patients without a dominant eye underwent 10 mm of BLR. Those with a dominant eye underwent the unilateral RR procedure on the nondominant eye according to the surgical dosage in Table 1 based on the largest angle of preoperative deviation measured at distance or near.
| Prism Diopters | Lateral Rectus Recession-Medial Rectus Resection (mm) |
|---|---|
| 40 | 8.0/6.0 |
| 45 | 8.5/6.0 |
| 50 | 9.0/7.0 |
Postoperative Measurements
Postoperative assessments were made at 1, 6 and 12 months and then every 1 year after the operation. Postoperative examinations were performed in the same manner as the preoperative examinations. Patients with diplopia associated with postoperative esotropia were managed with full-time alternating (after BLR) or monocular (fellow eye after the unilateral RR procedure) patching for 1 to 4 weeks until diplopia resolved. If the postoperative esotropia still existed at 1 month after the operation, hyperopia > +1.00 D was corrected and base-out Fresnel press-on prisms (3M Health Care, St. Paul, Minnesota) were prescribed to facilitate constant fusion. When it became evident that prisms would have to be worn for several months, prism-incorporated regular spectacles were prescribed. No patients needed bifocal correction.
Surgical outcome was considered satisfactory if the alignment was between 10 PD of exophoria/tropia and 5 PD of esophoria/tropia at distance in the primary position. Recurrence was defined as an alignment of >10 PD of exophoria/tropia, and overcorrection was defined as >5 PD of esophoria/tropia. Reoperation for overcorrected patients was performed if esotropia ≥20 PD persisted or increased for 6 months after surgery. Reoperation for recurrent exotropia was recommended in constant exotropia of ≥14 PD at distance or near, despite any nonsurgical treatments, such as part-time occlusion or minus-lens therapy. Improved stereopsis was defined as an improvement of more than 10 seconds of arc after the operation, and decreased stereopsis was defined as a deterioration of more than 10 seconds of arc.
Main Outcome Measures
Primary outcome measures were long-term surgical success based on postoperative alignment at distance and improvement in stereopsis. Secondary outcome measures were risk factors for recurrence and overcorrection.
Statistical Analysis
The student t test, chi-square test, Fisher exact test, and Mann-Whitney U test were used to compare the patients’ characteristics and the surgical outcomes. Univariate and multivariate analyses by linear logistic regression were performed to identify significant risk factors affecting surgical outcomes. Kaplan-Meier survival analysis and the log rank test were used to compare the long-term cumulative probability of achieving successful alignment between the 2 groups. A P value of <0.05 was considered statistically significant, and all analyses were performed with SPSS for Windows v 21.0 (SPSS, Chicago, Illinois).
Results
Preoperative Patient Characteristics
Among 121 consecutive children with primary large-angle exotropia who underwent surgery at Seoul National University Bundang Hospital between 2007 and 2009, 35 patients were excluded from analyses for the following reasons: insufficient follow-up period (8); congenital anomalies (10); neurologic disorder (11); and moderate to severe amblyopia (6). We included 48 patients who underwent BLR (the BLR group) and 38 patients who underwent the unilateral RR procedure (the RR group). The mean age of all patients at surgery was 6.1 ± 2.9 years. The preoperative patient characteristics were not significantly different in the 2 groups ( Table 2 ). The maximum preoperative angle of deviation was 43.8 ± 3.7 PD in the BLR group and 42.0 ± 3.1 PD in the RR group.
| BLR Group (n = 48) | RR group (n = 38) | P Value | |
|---|---|---|---|
| Gender (M:F) | 18:30 | 18:20 | .386 a |
| Mean age at onset of deviation (years) | 3.1 ± 3.3 | 3.8 ± 2.4 | .277 b |
| Mean age at surgery (years) | 5.8 ± 3.3 | 6.5± 3.0 | .300 b |
| Mean duration from onset of deviation to surgery (years) | 2.5 ± 1.9 | 2.8 ± 2.3 | .536 b |
| Maximum preoperative angle of deviation (PD) | 43.8 ± 3.7 | 42.0 ± 3.1 | .073 b |
| Fixation preference | 8 (16.7%) | 32 (84.2%) | <.001 a |
| Stereopsis status | |||
| ≤100 seconds | 41 (91.1%) | 31 (81.6%) | .342 a |
| >100 seconds | 4 (8.9%) | 7 (18.4%) | .330 c |
| Type of exodeviation | |||
| Intermittent exotropia | 26 (54.2%) | 20 (52.6%) | .887 a |
| Constant exotropia | 22 (45.8%) | 18 (47.4%) | .887 a |
| Associated features | |||
| Mild amblyopia | 0 | 5 (13.2%) | .015 c |
| Spherical equivalent, OD | −0.10 ± 1.36 | −0.55 ± 2.00 | .183 b |
| Spherical equivalent, OS | −0.09 ± 1.29 | −0.56 ± 1.96 | .165 b |
| Anisometropia >1.50 diopters | 0 | 0 | 1.0 c |
| Vertical strabismus | 2 (4.2%) | 0 | .500 c |
| A or V pattern | 1 (2.1%) | 0 | 1.0 c |
| Lateral incomitancy | 1 (2.1%) | 1 (2.6%) | 1.0 c |
| Dissociated vertical deviation | 1 (2.1%) | 1 (2.6%) | 1.0 c |
| Inferior oblique overaction | 11 (22.9%) | 9 (23.7%) | 1.0 c |
| Reoperation | 10 (20.8%) | 6 (15.8%) | .751 a |
| Time to recurrence after initial surgery (months) e | 5.5 ± 6.3 (n = 16, 33.3%) | 20.4 ± 17.8 (n = 10, 26.3%) | .013 d |
| Time to reoperation after initial surgery (months) | 25.1 ± 16.2 (n = 10, 20.8%) | 31.8 ± 12.9 (n = 6, 15.8%) | .330 d |
| Follow-up period (months) | 31.7 ± 8.5 | 35.2 ± 8.4 | .061 b |
e Time to recurrence of >10 PD of exophoria/tropia after initial surgery
Surgical Outcome
At 2 years after surgery, 29 of 48 (60.4%) patients in the BLR group had ocular alignment meeting the defined criteria of success, 16 patients (33.3%) had recurrence, and 3 patients (6.3%) had overcorrection ( Table 3 ). In the RR group, 18 of 38 (47.4%) patients had successful alignment, 10 patients (26.3%) had recurrence, and 10 patients (26.3%) were overcorrected. Until 2 years after surgery, the overcorrection rate was significantly higher in the RR group ( P = .014). However, after wearing base-out prism glasses or patching, 11 of 13 initially overcorrected patients (84.6%) in the RR group had <5 PD of esotropia at the last follow-up examination. At the final examination after a mean follow-up of 2.8 years, the successful alignment ( P = .371) and overcorrection ( P = 1.000) rates were comparable in both groups.
| Successful Alignment | Recurrence | Overcorrection | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 m | 6 m | 2 y | Final | 1 m | 6 m | 2 y | Final | 1m | 6m | 2y | Final | |
| BLR group (n, %) | 28 (58.3) | 30 (62.5) | 29 (60.4) | 29 (60.4) | 17 (35.4) | 15 (31.3) | 16 (33.3) | 16 (33.3) | 3 (6.3) | 3 (6.3) | 3 (6.3) | 3 (6.3) |
| RR group (n, %) | 25 (65.8) | 19 (50.0) | 18 (47.4) | 26 (68.4) | 1 (2.6) | 6 (15.8) | 10 (26.3) | 10 (26.3) | 12 (31.6) | 13 (34.2) | 10 (26.3) | 2 (5.3) |
| P value | .630 a | .346 a | .323 a | .371 a | 0 b | .131 b | .640 a | .640 a | .003 b | .002 b | .014 b | 1.0 b |
Surgical outcomes according to the magnitude of preoperative deviation at the final examination are summarized in Table 4 and Figure 1 . In patients with an exodeviation of 40 PD, the rates of achieving successful alignment were similar in the BLR and RR groups ( P = .070). However, in patients with an exodeviation of ≥45 PD, the RR group (90.0%) showed higher rates of successful alignment than did the BLR group (31.8%) at the final examination ( P = .006).
