Purpose
To determine predictors of reoperation and abnormal binocularity outcomes (including amblyopia and diplopia) following pediatric strabismus surgery.
Design
Retrospective cross-sectional study.
Methods
setting : Review of a national insurance database. study population : Children under age 18 years having strabismus procedures between 2007 and 2013. interventions : Adjustable- or fixed-suture strabismus surgery, or botulinum toxin injection. outcome measures : Reoperation or diagnosis of abnormal binocularity in the first postoperative year.
Results
Of 11 115 children having strabismus procedures, 851 (7.7%) underwent reoperation. The reoperation rate was 7.4% for fixed-suture surgeries, 9.6% for adjustable-suture surgeries ( P = .18), and 44.9% for botulinum injections ( P < .001). Age under 2 years was associated with higher reoperation and abnormal binocularity rates ( P < .001). For horizontal strabismus, the postoperative abnormal binocularity rate was 12.8% for fixed-suture surgery and 26.5% for botulinum injection ( P = .005). Reoperation rates tended to be higher with adjustable sutures (odds ratio [OR] 1.69, 95% confidence interval [CI] 0.94-3.03, P = .08) or botulinum toxin injection (OR 10.36, 95% CI 5.75-18.66, P < .001) and lower with 3- or 4-muscle surgery ( P = .001). Esotropia, hyperopia, and botulinum injection were independently associated with higher rates of postoperative abnormal binocularity ( P ≤ .005). For vertical surgeries, predictors of reoperation were adjustable-suture use (OR 2.51, P = .10) and superior oblique surgery (OR 2.36, P < .001).
Conclusions
Adjustable sutures were not associated with a lower reoperation rate in children. Younger age, esotropia, hyperopia, and botulinum injection were associated with postoperative abnormal binocularity. Superior oblique surgery and botulinum injection were associated with higher rates of reoperation.
Surgical correction of childhood strabismus can produce proper eye alignment and facilitate the development of binocular vision. Surgical strategies include conventional fixed-suture strabismus surgery, adjustable-suture surgery, and extraocular muscle botulinum toxin injection.
The approach to strabismus can involve some flexibility in selecting muscles for surgery. For instance, 1- vs 2-muscle surgery for smaller-angle strabismus has been debated. Similarly, whether to operate on 2, or more than 2, muscles in large-angle esotropia is not well defined. In addition, for exotropia, unilateral 2-muscle surgery has been found to have a lower reoperation rate than bilateral single-muscle surgery in a retrospective review of adult surgery and in randomized trials that included primarily children.
In addition to selecting muscles on which to operate, the surgeon must decide whether to place fixed or adjustable sutures. Adjustable-suture strabismus surgery offers the opportunity to refine the muscle position in the immediate postoperative period. Adjustable surgery has been advocated in children by several authors, but use in this age group presents particular challenges. Children often have difficulty cooperating with visual target fixation when experiencing discomfort from surgery and residual effects from anesthesia. Increased anesthesia time to place the suture in the operating room, and to tie off or adjust the suture afterwards, can be required in younger children.
In addition to or in place of incisional surgery, the surgeon may inject botulinum toxin into the extraocular muscles. Botulinum injection by itself has been found to produce similar motor and sensory outcomes in children with persistent strabismus following incisional surgery. Extraocular muscle scarring is avoided, and the short procedure duration minimizes anesthesia time. The latter is particularly advantageous in patients under age 4 years, in whom general anesthesia might have deleterious effects on cognitive development. Unfortunately, botulinum toxin effects may not persist. To our knowledge, randomized comparisons of botulinum toxin with incisional surgery have not been published for primary pediatric strabismus procedures, although this is an area of active interest.
We studied the outcome of pediatric strabismus procedures by determining reoperation rates (a motor outcome) and abnormal binocularity (a sensory outcome) in a large national insurance database.
Methods
This retrospective population-based cross-sectional study was approved by the Office of Research Subjects Protection of the Virginia Commonwealth University. The study used the MarketScan Commercial Claims and Encounters and the Medicare Supplemental and Coordination of Benefit databases (Truven Health Analytics, Ann Arbor, Michigan, USA) from the years 2007 through 2013 (the most recent year the databases were available). The MarketScan family of databases comprises the largest convenience-based proprietary database in the United States, annually encompassing approximately 50 million patients with employer-sponsored or supplemental insurance. These databases consist of de-identified, individual-level health records (inpatient and outpatient), obtained from large employers, hospitals, and Medicare programs. Additional details regarding the MarketScan databases, sampling methodologies, and limitations are described elsewhere. These databases have been used to report various ophthalmic treatment outcomes, including strabismus surgery reoperation in adults.
We searched the databases for children under age 18 having strabismus procedures. The procedure (coded using the Current Procedural Terminology, CPT) and diagnosis (coded using the International Classification of Disease, ICD-9) were noted. Strabismus procedures included horizontal (CPT 67311, 67312) or vertical (CPT 67314, 67316, 67318) muscle surgery or botulinum toxin injection (CPT 67345) on 1 or both eyes. We only included patients who had insurance for a full year postoperatively. We excluded patients having an index surgery diagnosis code for nystagmus (ICD 379.50-379.56).
We identified patients having a reoperation (a motor outcome), a diagnosis of abnormal binocularity (a sensory outcome), or either of these outcomes in the first year after surgery. We counted either horizontal or vertical procedures as reoperations, as done previously. In the present study, any additional incisional strabismus surgery or botulinum injection within the first year counted as a reoperation. All of these procedures usually involve general anesthesia in children. For combined horizontal plus vertical surgeries, it was not clear from the claim whether the adjustable suture was used for a horizontal or a vertical muscle. Moreover, owing to half-tendon width and other transpositions, and for other reasons, horizontal muscle surgery might influence vertical alignment, and vice-versa. Abnormal binocularity was defined to include office visit claims of amblyopia, diplopia, or anomalous retinal correspondence ( Table 1 ).
| Patient Category | Definition |
|---|---|
| Esotropia | ICD 378.00-378.08, 378.21, 378.22, 378.35, 378.41, 378.54, 378.84 |
| Exotropia | ICD 378.10-378.18, 378.23, 378.24, 378.42, 378.81, 378.83, 378.86 |
| Refractive asymmetry | Aniseikonia (ICD 367.32), anisometropia (367.31) |
| Myopia subtypes | Myopia (ICD 367.1), progressive high myopia (360.21) |
| Abnormal binocularity | Amblyopia: unspecified (ICD 368.00), strabismic (368.01), deprivation (368.02), refractive (368.03), diplopia (368.2), 368.30 (binocular vision disorder unspecified), 368.31 (suppression of binocular vision), 368.32 (simultaneous visual perception without fusion), 368.33 (fusion with defective stereopsis), 368.34 (abnormal retinal correspondence) |
In the analysis comparing horizontal strabismus surgery and botulinum toxin injection, patients had to have a diagnosis code consistent with esotropia, exotropia, or Duane syndrome (ICD 378.71, Table 1 ). Without these diagnosis codes, it is unclear if an injection was for a horizontal or vertical deviation.
Variables associated with outcomes in the first year were determined. Patient groupings for univariate analysis included age (0-1, 2-4, 5-8, and 9-17 years), use of adjustable suture (CPT 67335), number of muscles operated, and several procedure and diagnosis categories ( Table 1 ). The following strabismus types were defined as previously: complex, incomitant, paralytic, alternating, A or V pattern, mechanical, intermittent. As previously, monocular deviation was defined as ICD 378.01-378.04, 378.11-378.14, or 378.34. Diagnosis codes for refractive error (eg, hyperopia, ICD 367.0, and regular astigmatism, 367.21) and abnormal binocularity were identified in the claims record, which included office visits, in the 2 years prior to surgery ( Table 1 ).
The patient was included in the adjustable suture group if an adjustable suture was used on any muscle, even if other muscles in the same or the contralateral eye were sutured in the conventional fashion. Because adjustable sutures are not typically used for oblique muscle surgery, we performed secondary analyses that excluded patients having superior oblique surgery (CPT 67318) or fourth nerve palsy (ICD 378.53).
Proportions were compared by the Fisher exact test. A multivariable logistic regression model was prepared in a stepwise backwards fashion. Stated odds ratios (OR) and 95% confidence intervals (CI) apply to multivariable analysis. Analysis was performed in SPSS (version 22; SPSS Inc, Chicago, Illinois, USA).
Results
Overall Analysis of All Patients
Of 11 115 total children who underwent strabismus procedures, 7.7% had a reoperation, 12.1% had abnormal binocularity, and 18.2% had either (or both) of these outcomes in the first postoperative year ( Table 2 ).
| Type of Surgery | Total | Reoperation | Abnormal Binocularity | Reoperation or Abnormal Binocularity | |||
|---|---|---|---|---|---|---|---|
| N | N | % | N | % | N | % | |
| Fixed-suture surgery | 10 806 | 804 | 7.4% | 1313 | 12.2% | 1955 | 18.1% |
| Adjustable-suture surgery | 260 | 25 | 9.6% | 24 | 9.2% | 45 | 17.3% |
| Botulinum injection only | 49 | 22 | 44.9% | 13 | 26.5% | 25 | 51.0% |
| Total | 11 115 | 851 | 7.7% | 1350 | 12.1% | 2025 | 18.2% |
Younger age was consistently associated with reoperation and abnormal binocularity. For instance, children under age 2 had an odds ratio for reoperation of 3.24 compared with children age 5-17, and an odds ratio for abnormal binocularity of 2.34 compared with children age 9-17 ( Supplemental Tables 1 and 2 ; Supplemental Material available at AJO.com , both P < .001).
Only 2.3% of incisional surgeries in this sample were performed in an adjustable fashion ( Table 2 ). Reoperations were performed after 9.6% of adjustable-suture surgeries and after 7.4% of fixed-suture surgeries ( P = .19, Table 2 ). After controlling for age and other factors, adjustable sutures were associated with a higher rate of reoperation (multivariable OR 1.65, 95% CI 1.08-2.54, P = .02, Supplemental Table 1 ). Postoperatively, reoperation and/or abnormal binocularity occurred in 17.3% of adjustable-suture surgery patients and in 18.1% of fixed-suture patients ( P = .81, Table 2 ). The combined outcome of reoperation and/or abnormal binocularity with adjustable sutures did not differ significantly from that with fixed sutures (OR 1.16, 95% CI 0.82-1.63, P = .41, Supplemental Table 3 ; Supplemental Material available at AJO.com ).
Because adjustable sutures are infrequently used for oblique muscle surgery, we repeated the analysis after exclusion of surgeries of the superior oblique or for fourth nerve palsy. Reoperations were performed after 8.2% of adjustable-suture surgeries (20 of 244) and after 7.1% of fixed-suture surgeries (705 of 9950, P = .53). The association of adjustable sutures with reoperations was not statistically significant (multivariable OR 1.47, 95% CI 0.91-2.36, P = .11). Postoperatively, reoperation and/or abnormal binocularity occurred in 16.4% of adjustable-suture surgery patients and in 18.0% of fixed-suture patients ( P = .56, Supplemental Tables 1 and 4 ; Supplemental Material available at AJO.com ). The combined outcome of reoperation and/or abnormal binocularity with adjustable sutures did not differ significantly from that with fixed sutures (OR 1.08, 95% CI 0.75-1.56, P = .67, Supplemental Table 3 ).
Abnormal binocularity before surgery was associated with a slight tendency to fewer reoperations (OR 0.78, P = .01), but was strongly associated with a higher probability of abnormal binocularity postoperatively (OR 7.38, 95% CI 6.52-8.36, P < .001). Vertical surgery was associated with a higher likelihood of reoperation (OR 1.39, P < .001; Supplemental Tables 1 and 2 ).
Because botulinum injection was used only for horizontal surgery, and because a previous analysis demonstrated effect modification for the association of adjustable surgery with reoperation rate depending on whether a horizontal or vertical surgery was performed, we present below separate analyses of isolated horizontal and vertical muscle surgery.
Isolated Horizontal Muscle Procedures
Of 7740 children having procedures exclusively on horizontal muscles, 6.7% had a reoperation, 12.7% had abnormal binocularity, and 18.1% had either (or both) of these outcomes in the first postoperative year ( Tables 3 and 4 , and Supplemental Table 5 ; Supplemental Material available at AJO.com ). The CPT code often applied with scarring due to prior surgery (67332) was used in 1015 cases (13%; Supplemental Table 6 ; Supplemental Material available at AJO.com ). Only 1 patient had the -58 modifier to indicate a planned reoperation.
| Clinical Factor | Reoperation (%) | Multivariable Analysis | |
|---|---|---|---|
| Odds Ratio (95% CI) | P Value | ||
| Age 5-17 years | 5.0% (228/4551) | 1.00 (reference) | — |
| Age 2-4 years | 6.9% (162/2352) | 1.35 (1.09-1.67) | .005 |
| Age 0-1 year | 15.4% (129/836) | 3.33 (2.63-4.21) | <.001 |
| Fixed suture | 6.4% (484/7521) | 1.00 (reference) | — |
| Adjustable suture | 7.6% (13/170) | 1.69 (0.94-3.03) | .08 |
| Botulinum toxin only | 44.9% (22/49) | 10.36 (5.75-18.66) | <.001 |
| 3 or 4 muscles operated | 3.7% (44/1178) | 0.58 (0.42-0.80) | .001 |
| Monocular deviation | 4.7% (56/1192) | 0.75 (0.56-1.00) | .049 |
| Astigmatism | 15.9% (10/63) | 2.85 (1.40-5.74) | .004 |
| Abnormal binocularity, preoperative | 5.2% (81/1571) | 0.74 (0.58-0.95) | .02 |
| Total | 6.7% (519/7740) | — | — |
| Clinical Factor | Abnormal Binocularity (%) | Multivariable Analysis | |
|---|---|---|---|
| Odds Ratio (95% CI) | P Value | ||
| Age 9-17 years | 7.7% (174/2260) | 1.00 (reference) | — |
| Age 0-8 years | 14.8% (812/5480) | 1.82 (1.50-2.19) | <.001 |
| Fixed suture | 12.8% (959/7521) | 1.00 (reference) | — |
| Botulinum toxin only | 26.5% (13/49) | 2.75 (1.36-5.56) | .005 |
| Adjustable suture | 8.2% (14/170) | 0.66 (0.36-1.20) | .17 |
| 3 or 4 muscles operated | 16.9% (199/1178) | 1.40 (1.16-1.70) | <.001 |
| Esotropia | 16.4% (667/4072) | 1.51 (1.29-1.76) | <.001 |
| Astigmatism | 28.6% (18/63) | 2.80 (1.57-5.15) | <.001 |
| Abnormal binocularity, preoperative | 36.3% (570/1571) | 7.15 (6.17-8.28) | <.001 |
| Hyperopia | 25.4% (93/366) | 1.74 (1.32-2.30) | <.001 |
| Refractive asymmetry | 33.9% (20/59) | 2.00 (1.08-3.70) | .03 |
| Total | 12.7% (986/7740) | — | — |
Younger age was associated with a higher rate of reoperation and abnormal binocularity. The reoperation rate decreased progressively from 15.4% for those under age 2 to 5.0% for those over age 4 ( P < .001, Table 3 ). Similarly, the likelihood of abnormal binocularity in the first postoperative year decreased from 14.8% for those under age 9 to 7.7% for those aged 9-17 ( P < .001, Table 4 ).
The reoperation rate was 7.4% with 1 muscle operated (106 of 1434) and 6.8% with 2 muscles operated (347 of 5079, P = .48, Supplemental Table 7 ; Supplemental Material available at AJO.com ). The rate of abnormal binocularity after surgery was 9.3% with 1 muscle operated (134 of 1434) and 12.6% with 2 muscles operated (640 of 5079, P = .001, Supplemental Table 6 ). As compared with 1- or 2-muscle surgery, operating on 3 or 4 muscles had a lower reoperation rate of 3.7% ( P = .001, Table 3 ) but a higher rate of abnormal postoperative binocularity of 16.9% ( P < .001, Table 4 ).
Unilateral surgery on 2 horizontal muscles comprised only 9.1% of horizontal cases, while bilateral 1-muscle surgery comprised 56.5% of horizontal cases. There was no significant difference in reoperation rate with unilateral surgery on 2 horizontal muscles (6.0%) compared with bilateral surgery on 1 horizontal muscle (7.0%, P = .16, Supplemental Table 7 ). With separate evaluations of esotropia and of exotropia, these 2 types of 2-muscle surgery continued to have similar reoperation rates ( Supplemental Table 8 ; Supplemental Material available at AJO.com ). For exotropia, the reoperation rate was 6.0% with bilateral 1-muscle surgery (117 of 1953) and was 5.3% with unilateral 2-muscle surgery (20 of 375, P = .72, Supplemental Table 8 ; Supplemental Material available at AJO.com ). The rate of postoperative abnormal binocularity was also similar with bilateral 1-muscle surgery (12.3%, 539 of 4374) and unilateral 2-muscle surgery (14.3%, 101 of 705, P = .14, Supplemental Table 6 ).
The reoperation rate in the first postoperative year was 7.6% with adjustable sutures (13 of 170) and 6.4% with fixed sutures (484 of 7521, P = .53, Supplemental Table 5 , Figure ). After controlling for relevant factors, the reoperation rate with adjustable sutures was not significantly different (multivariable OR 1.69, 95% CI 0.94-3.03, P = .08, Table 3 ). The 8.2% rate of abnormal binocularity with adjustable sutures tended to be lower than the 12.8% seen with fixed sutures (multivariable OR 0.66, P = .17, Table 4 ). The combined outcome of reoperation and/or abnormal binocularity was not significantly different with adjustable sutures (15.3%, multivariable OR 1.04, 95% CI 0.66-1.62, P = .88) compared with fixed sutures (17.9%, Supplemental Tables 5 and 9 ; Supplemental Material available at AJO.com ).
There was no benefit of adjustable sutures in an analysis restricted to older patients. For instance, in patients aged 5-17 with 1- or 2-muscle surgery, and none of the risk factors associated with reoperation, the reoperation rate was 11.6% with adjustable sutures (8 of 69 patients) and actually tended to be lower with the fixed-suture technique (5.7%, 69 of 1204, P = .06, Supplemental Table 10 ; Supplemental Material available at AJO.com ).
Patients with monocular deviation had a reoperation rate of 4.7%, slightly less than comparison cases (OR 0.75, P = .049, Table 3 ). Patients with claims for astigmatism had higher rates of both reoperation (OR 2.85) and abnormal binocularity after surgery (OR 7.15, P ≤ .004, Tables 3 and 4 ). Horizontal surgery patients with abnormal binocularity before surgery or having 3 or 4 muscles operated had slightly lower rates of reoperation (OR 0.74 and 0.58, respectively), but had higher rates of postoperative abnormal binocularity (OR 7.15 and 1.40, respectively, Tables 3 and 4 ). Paralytic deviations had a rate of reoperation of 11.1%, which was significantly elevated in the univariate analysis only ( P = .01, Supplemental Table 7 ).
Compared with the overall rate of postoperative abnormal binocularity of 12.7%, significantly elevated rates were seen in patients with esotropia (16.4%), and claims for hyperopia (25.4%) and interocular refractive asymmetry (33.9%, all P ≤ .03, Table 4 ). Intermittent deviations had a rate of postoperative abnormal binocularity of 9.9%, which was lower than expected in the univariate analysis only ( P = .007, Supplemental Table 6 ).
Botulinum toxin injection was used only for horizontal cases. Eight children (0.1%) had incisional horizontal surgery, while 49 children (0.6%) had botulinum injection alone ( Supplemental Table 5 ). Of these 49 injected children, 22 (44.9%) had reoperation, 13 (26.5%) had abnormal binocularity, and 25 (51.0%) had either (or both) of these outcomes ( Figure , Tables 3 and 4 , Supplemental Table 5 ). In contrast, following incisional surgery, 6.5% of children had reoperation and 12.7% had abnormal binocularity ( Supplemental Table 5 ). As compared with fixed-suture surgery, botulinum injection had an odds ratio for reoperation of 10.36 (95% CI 5.75-18.66) and an odds ratio for postoperative abnormal binocularity of 2.75 (95% CI 1.36-5.56, both P ≤ .005, Tables 3 and 4 ).
The strabismus etiology was identified as paralytic in 20.4% of the cases involving botulinum toxin injection (10 of 49 cases). When presence or absence of a paralytic etiology was forced into the multivariable regression model, botulinum injection still had an odds ratio for reoperation of 9.77 (95% CI 5.40-17.67, P < .001) and an odds ratio for postoperative abnormal binocularity of 2.78 (95% CI 1.37-5.65, P = .005).
Isolated Vertical Muscle Surgery
Of 1534 children having procedures exclusively on vertical muscles, 11.0% had a reoperation, 10.0% had abnormal binocularity, and 18.6% had either (or both) of these outcomes in the first postoperative year ( Tables 5 and 6 ).
| Clinical Factor | Reoperation (%) | Multivariable Analysis | |
|---|---|---|---|
| Odds Ratio (95% CI) | P Value | ||
| Age 5-17 years | 7.1% (68/958) | 1.00 (reference) | — |
| Age 2-4 years | 14.6% (58/398) | 1.86 (1.22-2.82) | .004 |
| Age 0-1 year | 23.6% (42/178) | 4.41 (2.68-7.28) | <.001 |
| Fixed suture | 10.8% (163/1512) | 1.00 (reference) | — |
| Adjustable suture | 22.7% (5/22) | 2.51 (0.85-7.38) | .10 |
| Superior oblique surgery | 20.6% (46/223) | 2.36 (1.61-3.46) | <.001 |
| Total | 11.0% (168/1534) | — | — |
| Clinical Factor | Abnormal Binocularity (%) | Multivariable Analysis | |
|---|---|---|---|
| Odds Ratio (95% CI) | P Value | ||
| Age 9-17 years | 6.7% (35/524) | 1.00 (reference) | — |
| Age 2-8 years | 11.1% (92/832) | 2.61 (1.68-4.07) | <.001 |
| Age 0-1 year | 15.2% (27/178) | 4.25 (2.36-7.65) | <.001 |
| Fixed suture | 9.8% (148/1512) | 1.00 (reference) | — |
| Adjustable suture | 27.3% (6/22) | 3.46 (1.19-10.08) | .02 |
| Myopia, any type | 27.6% (8/29) | 3.76 (1.42-9.99) | .008 |
| Abnormal binocularity, preoperative | 29.5% (82/278) | 7.99 (5.53-11.56) | <.001 |
| Total | 10.0% (154/1534) | — | — |
Children under age 2 years had a reoperation in 23.6% of the cases (OR 4.41, P < .001). Surgery involving the superior oblique muscle involved reoperation in 20.6% of cases, and was an independent risk factor for reoperation (OR 2.36, 95% CI 1.61-3.46, P < .001). In a univariate analysis, surgery for Brown syndrome was associated with a reoperation rate of 23.0% (17 of 74 cases, P = .002, Supplemental Tables 11 and 12 ; Supplemental Material available at AJO.com ).
Adjustable-suture surgery resulted in a reoperation rate of 22.7% (5 of 22 cases, OR 2.51, 95% CI 0.85-7.38, P = .10, Table 5 ). Adjustable-suture surgery was associated more frequently with reoperation and/or abnormal binocularity (OR 2.61, 95% CI 1.02-6.69, P = .045, Supplemental Table 13 ; Supplemental Material available at AJO.com ). With exclusion of superior oblique surgery and fourth nerve palsy, adjustable sutures were not significantly associated with reoperation (OR 1.26, 95% CI 0.27-5.97, P = .77, Supplemental Tables 14 and 15 ; Supplemental Material available at AJO.com ) or the combined outcome of reoperation and/or abnormal binocularity (OR 2.11, P = .20, Supplemental Tables 13-18 ; Supplemental Material available at AJO.com ).
Myopia and preoperative abnormal binocularity were associated with a higher rate of abnormal binocularity following vertical muscle surgery ( P ≤ .008, Table 6 ). The number of claims involving a code for myopia was small, making this finding uncertain.
Results
Overall Analysis of All Patients
Of 11 115 total children who underwent strabismus procedures, 7.7% had a reoperation, 12.1% had abnormal binocularity, and 18.2% had either (or both) of these outcomes in the first postoperative year ( Table 2 ).
| Type of Surgery | Total | Reoperation | Abnormal Binocularity | Reoperation or Abnormal Binocularity | |||
|---|---|---|---|---|---|---|---|
| N | N | % | N | % | N | % | |
| Fixed-suture surgery | 10 806 | 804 | 7.4% | 1313 | 12.2% | 1955 | 18.1% |
| Adjustable-suture surgery | 260 | 25 | 9.6% | 24 | 9.2% | 45 | 17.3% |
| Botulinum injection only | 49 | 22 | 44.9% | 13 | 26.5% | 25 | 51.0% |
| Total | 11 115 | 851 | 7.7% | 1350 | 12.1% | 2025 | 18.2% |
Younger age was consistently associated with reoperation and abnormal binocularity. For instance, children under age 2 had an odds ratio for reoperation of 3.24 compared with children age 5-17, and an odds ratio for abnormal binocularity of 2.34 compared with children age 9-17 ( Supplemental Tables 1 and 2 ; Supplemental Material available at AJO.com , both P < .001).
Only 2.3% of incisional surgeries in this sample were performed in an adjustable fashion ( Table 2 ). Reoperations were performed after 9.6% of adjustable-suture surgeries and after 7.4% of fixed-suture surgeries ( P = .19, Table 2 ). After controlling for age and other factors, adjustable sutures were associated with a higher rate of reoperation (multivariable OR 1.65, 95% CI 1.08-2.54, P = .02, Supplemental Table 1 ). Postoperatively, reoperation and/or abnormal binocularity occurred in 17.3% of adjustable-suture surgery patients and in 18.1% of fixed-suture patients ( P = .81, Table 2 ). The combined outcome of reoperation and/or abnormal binocularity with adjustable sutures did not differ significantly from that with fixed sutures (OR 1.16, 95% CI 0.82-1.63, P = .41, Supplemental Table 3 ; Supplemental Material available at AJO.com ).
Because adjustable sutures are infrequently used for oblique muscle surgery, we repeated the analysis after exclusion of surgeries of the superior oblique or for fourth nerve palsy. Reoperations were performed after 8.2% of adjustable-suture surgeries (20 of 244) and after 7.1% of fixed-suture surgeries (705 of 9950, P = .53). The association of adjustable sutures with reoperations was not statistically significant (multivariable OR 1.47, 95% CI 0.91-2.36, P = .11). Postoperatively, reoperation and/or abnormal binocularity occurred in 16.4% of adjustable-suture surgery patients and in 18.0% of fixed-suture patients ( P = .56, Supplemental Tables 1 and 4 ; Supplemental Material available at AJO.com ). The combined outcome of reoperation and/or abnormal binocularity with adjustable sutures did not differ significantly from that with fixed sutures (OR 1.08, 95% CI 0.75-1.56, P = .67, Supplemental Table 3 ).
Abnormal binocularity before surgery was associated with a slight tendency to fewer reoperations (OR 0.78, P = .01), but was strongly associated with a higher probability of abnormal binocularity postoperatively (OR 7.38, 95% CI 6.52-8.36, P < .001). Vertical surgery was associated with a higher likelihood of reoperation (OR 1.39, P < .001; Supplemental Tables 1 and 2 ).
Because botulinum injection was used only for horizontal surgery, and because a previous analysis demonstrated effect modification for the association of adjustable surgery with reoperation rate depending on whether a horizontal or vertical surgery was performed, we present below separate analyses of isolated horizontal and vertical muscle surgery.
Isolated Horizontal Muscle Procedures
Of 7740 children having procedures exclusively on horizontal muscles, 6.7% had a reoperation, 12.7% had abnormal binocularity, and 18.1% had either (or both) of these outcomes in the first postoperative year ( Tables 3 and 4 , and Supplemental Table 5 ; Supplemental Material available at AJO.com ). The CPT code often applied with scarring due to prior surgery (67332) was used in 1015 cases (13%; Supplemental Table 6 ; Supplemental Material available at AJO.com ). Only 1 patient had the -58 modifier to indicate a planned reoperation.
