Journal of Pediatric Ophthalmology and Strabismus

Original Article 

Effects of Surgical Timing on Surgical Success and Long-term Motor and Sensory Outcomes of Infantile Esotropia

Omer Ersin Muz, MD, MRCESd (Ophth); Ali Sefik Sanac, MD

Abstract

Purpose:

To investigate the effect of surgical timing on long-term motor and sensory outcomes in patients with infantile esotropia.

Methods:

The medical records of patients who underwent strabismus surgery for infantile esotropia were reviewed retrospectively. The patients were divided into three groups according to age at the time of surgery: early group (6 to 11 months), late group (12 to 17 months), and very late group (18 to 27 months). The main outcome measures were final alignment, surgical success rate (the angle of deviation at final follow-up of ≤ 10 prism diopters [PD] of esotropia, no exotropia and no need for reoperation), stereoacuity, visual acuity, and the number of reoperations required during the follow-up.

Results:

A total of 79 patients (44 female, 35 male) met the inclusion criteria. The surgical success rate was 25.9%, 23.1%, and 53.8% in the three groups, respectively (P = .035). After a mean follow-up of 96 months, the average number of operations per child was 1.7 ± 0.9, 1.6 ± 0.6, and 1.4 ± 0.6 in the three groups, respectively (P = .020). The measurable stereopsis rate was higher in the early group (37% vs 3.8% and 3.8%, respectively) (P = .001). The amblyopia rate was similar between groups.

Conclusions:

The results show that performing surgery later in life in patients with infantile esotropia increases the motor success rate of surgery. In addition, orthophoria is achieved with fewer surgical operations. However, earlier surgery may improve stereopsis.

[J Pediatr Ophthalmol Strabismus. 2020;57(5):319–325.]

Abstract

Purpose:

To investigate the effect of surgical timing on long-term motor and sensory outcomes in patients with infantile esotropia.

Methods:

The medical records of patients who underwent strabismus surgery for infantile esotropia were reviewed retrospectively. The patients were divided into three groups according to age at the time of surgery: early group (6 to 11 months), late group (12 to 17 months), and very late group (18 to 27 months). The main outcome measures were final alignment, surgical success rate (the angle of deviation at final follow-up of ≤ 10 prism diopters [PD] of esotropia, no exotropia and no need for reoperation), stereoacuity, visual acuity, and the number of reoperations required during the follow-up.

Results:

A total of 79 patients (44 female, 35 male) met the inclusion criteria. The surgical success rate was 25.9%, 23.1%, and 53.8% in the three groups, respectively (P = .035). After a mean follow-up of 96 months, the average number of operations per child was 1.7 ± 0.9, 1.6 ± 0.6, and 1.4 ± 0.6 in the three groups, respectively (P = .020). The measurable stereopsis rate was higher in the early group (37% vs 3.8% and 3.8%, respectively) (P = .001). The amblyopia rate was similar between groups.

Conclusions:

The results show that performing surgery later in life in patients with infantile esotropia increases the motor success rate of surgery. In addition, orthophoria is achieved with fewer surgical operations. However, earlier surgery may improve stereopsis.

[J Pediatr Ophthalmol Strabismus. 2020;57(5):319–325.]

Introduction

Infantile esotropia is defined as the onset of esotropia before 6 months of age with a constant large angle of strabismus (> 30 prism diopters [PD]) in the absence of neurologic disorders. One or more of the following, such as cross-fixation, no or mild amblyopia, small-to-moderate hypermetropia, latent nystagmus, dissociated vertical deviation, and absent or reduced binocular vision, may accompany the findings.1,2 Ocular alignment is rarely achieved spontaneously. Therefore, most patients require surgical alignment, especially those who have a constant esotropia of 40 PD with onset after 10 weeks of age.3,4

Similar to other aspects of vision, depth perception is not complete at birth and continues to develop throughout early and middle childhood.5 The critical period for the maturation of fusion is between 4 and 6 months old.5 For well-developed fusion in this period, structurally and functionally healthy eyes, visual pathways, and cortical functions are required.6 Patients with infantile esotropia usually do not have a good visual acuity or a high degree of fusion because their eyes were not aligned during development. The aim of surgical treatment in patients with infantile esotropia is to align the eyes as much as possible to achieve normal maturation of vision. Many studies emphasized the importance of minimizing the duration of misalignment through early correction of strabismus to have a well-developed stereopsis in infantile esotropia.7–9

In the current study, we aimed to provide a better understanding of the clinical spectrum of the disorder by comparing motor and sensory results in the long-term follow-up of patients who underwent surgery for infantile esotropia.

Patients and Methods

The medical records of patients who underwent strabismus surgery for infantile esotropia at the Department of Ophthalmology, Hacettepe University, Ankara, between 1985 and 2012 were retrospectively reviewed. This study was approved by the ethics board of our university and adhered to the tenets of the Declaration of Helsinki.

Records of the patients who underwent surgery for infantile esotropia before the age of 27 months were investigated. Patients who were followed up for a minimum of 24 months and whose visual acuity and binocular vision levels were evaluated at the last examination were included in the study. None of patients had neurologic abnormalities, premature birth, previous strabismus surgery, or other ocular pathologies.

At the time of diagnosis, non-accommodative esotropia occurring in the first 6 months of life in a neurologically intact child was considered infantile esotropia. When available, old photographs were taken into account to confirm the diagnosis. All patients had a full ophthalmic examination at the first and subsequent visits, including visual acuity, cycloplegic refraction, amblyopia assessment, horizontal deviation, ductions and versions, and sensory state. The presence of abnormal head position, nystagmus, vertical deviations, dissociated deviations, alphabetic variations (A- or V-pattern), and cross-fixation were recorded. In all visits, examinations of the anterior and posterior segments were also performed. The angle of deviation was measured by the prism and alternate cover test, when possible, at both distance and near after complete correction of the refractive error, when present. The Krimsky and Hirschberg tests were used in patients who could not adapt to the cover tests. The results were recorded in prism diopters.

All patients were evaluated by two pediatric ophthalmologists (ASS, ECS). More than one examination was performed before surgery to establish the correct measurements. All follow-up examinations and surgical interventions were performed by the same ophthalmologists.

Patients who had constant esodeviations of 30 PD or greater at the initial visit underwent surgery under general anesthesia. For horizontal deviation, two types of surgery were performed. Sixty-seven patients underwent bilateral medial rectus recession, and 12 patients underwent right or left eye medial rectus recession with lateral rectus resection. The surgical dosage table defined by Parks and Wheeler10 was used when planning the dosage of muscle recession and resection. In 23 patients, inferior oblique surgery was added to the horizontal rectus muscle surgery. Additional interventions were performed as needed for residual esotropia, consecutive exotropia, inferior oblique hyperfunction/hypofunction, or dissociated deviations.

The sensory state was measured by stereoacuity and assessed by the TNO test. The Worth 4-dot test was used in these patients to assess monofixation syndrome.

We defined amblyopia as a difference of at least two lines of best corrected visual acuity (BCVA) between eyes according to a Snellen chart at the final visit.

The patients were divided into three groups according to age at the time of surgery: early group (6 to 11 months), late group (12 to 17 months), and the very late group (18 to 27 months).

Surgical success was defined by the following criteria: successful (the final angle of horizontal deviation less than 10 PD of esotropia, no exotropia, and no need for retreatment), residual esotropia (the angle of deviation larger than 10 PD of esotropia), and consecutive exotropia (presence of exotropia). When evaluating the success of the surgery, the angle of deviation at the last examination was considered to be the final angle value. If more than one operation was performed, the angle value prior to the second operation was considered.

Results were analyzed using SPSS software (version 17; SPSS, Inc). Patient characteristics are presented with numbers and percentages for categorical variables and medians and ranges for continuous variables. In addition, the minimum and maximum values of the continuous variables are shown. The chi-square test and one-way analysis of variance were used to compare the variables according to the groups. P values less than .05 were considered significant.

Results

For the designated 17-year period of review, 44 female and 35 male patients who met the strict inclusion criteria were identified. Twenty-seven patients (34.2%) were in the early group, 26 (32.9%) were in the late group, and 26 (32.9%) were in the very late group. The mean age at the first examination was 7.6 ± 1.8 months (range: 3 to 11 months) in the early group, 12.2 ± 3.4 months (range: 3 to 17 months) in the late group, and 15.0 ± 6.0 months (range: 4 to 26 months) in the very late group (P < .001).

The average horizontal angle of deviation for all patients at baseline examination was 50.9 ± 14.0 PD and the refractive error range was −2.00 to +3.50 diopters (D) (average: +1.77 D).

The mean age at the first operation was 8.5 ± 1.6 months in the early group, 14.4 ± 2.0 months in the late group, and 20.9 ± 3.1 months in the very late group. The youngest and oldest patients at the time of surgery were 6 and 27 months old, respectively. The mean follow-up duration was 96.6 ± 40.0 months for all patients and 75% of patients were followed up for more than 60 months. No significant differences were determined among the groups for preoperative angle of horizontal deviation, refractive error, and follow-up duration (P > .05, for all). A comparison of the data for the three groups and the distribution of follow-up durations are summarized in Tables 12, respectively.

Patient Demographic Dataa

Table 1:

Patient Demographic Data

Distribution of Follow-up Durations According to the Groups

Table 2:

Distribution of Follow-up Durations According to the Groups

The clinical findings at baseline were recorded. In total, 6 patients had nystagmus except latent nystagmus, 35 patients had inferior oblique muscle overaction, 4 patients had V-pattern deviation, 27 patients had cross-fixation, and 7 patients had dissociated vertical deviation. Abnormal head position was detected in only 1 patient. The distribution of coexisting findings, except cross-fixation and dissociated vertical deviation, was similar among the groups. Dissociated vertical deviation was found slightly more frequently in the very late group, and cross-fixation was found more frequently in the late group (P = .045 and .005, respectively). The distribution of the clinical findings according to groups is shown in Table 3.

Coexisting Clinical Findings of Patients

Table 3:

Coexisting Clinical Findings of Patients

The mean final angle of horizontal deviation was 16.0 ± 10.6 PD in the early group, 11.4 ± 8.7 PD in the late group, and 10.7 ± 9.0 PD in the very late group (P = .403). Surgical success was achieved in 27 of 79 patients (34.2%). Forty-seven patients (59.5%) had residual esotropia and 5 (6.3%) had consecutive exotropia. The surgical success rate was 25.9% in the early group, 23.1% in the late group, and 53.8% in the very late group (P = .035).

A total of 35 patients (44.3%) underwent a second surgery. Nine patients (11.4%) underwent a third surgery and 1 patient required a fourth surgery during the follow-up period. The risk for undergoing a second surgery was not significantly different between the groups (P = .148), but 77.8% of those requiring a third surgery and the patient who underwent a fourth surgery were in the very early group. The average number of operations per child was 1.7 ± 0.9 in the early group, 1.6 ± 0.6 in the late group, and 1.4 ± 0.6 in the very late group (P = .020). The comparison of surgical success rates and numbers of required additional surgeries for the groups are summarized in Table 4. Because follow-up time may have a negative effect on the rates of surgical success and recurrent surgery, surgical success and reoperation rates were evaluated at the second month of follow-up and at the final visit. An increase in the rate of secondary surgery was noticed at the final visit compared to the second year of follow-up (44.3% vs 16.5%) (Table 5).

Comparison of Final Motor and Sensory Outcomes of Patients

Table 4:

Comparison of Final Motor and Sensory Outcomes of Patients

The Comparison of Results at the End of 24 Months of Follow-up and at the Final Visit

Table 5:

The Comparison of Results at the End of 24 Months of Follow-up and at the Final Visit

Amblyopia was found in 37 patients (46.8%): 13 (35.1%) were in early group, 13 (35.1%) were in the late group, and 11 (29.7%) were in the very late group (P = .845).

Twelve patients had measurable stereopsis according to the Titmus Fly test. In 10 patients (83.3%), stereopsis was limited to 3,000 seconds of arc (positive Fly test result). One patient had 300 seconds of arc stereopsis and one patient had 200 seconds of arc, which was the highest degree of stereopsis obtained. Ten patients (83.3%), including the patient who had the highest degree of stereo-acuity, were in early group. Stereopsis was detected in one patient in the late and very late groups. The measurable stereopsis rate was significantly better in the early group than in the other groups (P = .001).

Discussion

The critical period for the maturation of sensory fusion is between 4 and 6 months of age, and ocular alignment should be achieved in this period.5 With improvements in pediatric anesthesia making operations possible in the first 6 months of life, early surgical applications have become popular. Although early surgery is preferred, difficulties in intervention in the small size of an infant's eye and orbit and errors in preoperative measurements due to the incompatibility of the infants during the examination, can make it difficult to achieve successful surgical outcomes.6 Therefore, multiple operations may be required to obtain the desired results.

In our study, the results showed that performing surgery in patients older than 18 months increased the chance of motor success. In addition, patients who underwent surgery at a younger age were more likely to require additional operations. The average number of operations per child was 1.74 ± 0.94 in the early group, 1.61 ± 0.57 in the late group, and 1.35 ± 0.56 in the very late group. Louwagie et al11 reported that 51% of patients who underwent surgery for infantile esotropia needed additional surgical procedures within 10 years. In the same study, it was shown that this ratio increased to 66% in a 20-year follow-up period. It was revealed that a larger presenting angle of esotropia and a younger age at first surgery were associated with an increased risk for undergoing a second surgery. Trigler and Siatkowski12 compared reoperation rates according to age and reported that the number of patients requiring additional procedures increased when surgery was performed at the age of 15 months and younger (67% vs 47%). The European Early Versus Late Infantile Strabismus Surgery Study (ELISSS) investigated the results of 532 patients who underwent surgery for infantile esotropia in a prospective, controlled, and non-randomized multicenter trial.13 The study compared early and late surgery (6 to 24 months vs 32 to 60 months) and showed that the number of operations per child was 1.18 ± 0.67 in the early group and 0.99 ± 0.64 in the late group. According to studies that have short and medium follow-up results, the surgical success rate is between 70% and 90%.11,14–16 However studies that have long-term follow-up results present lower surgical success rates. It was also reported that repeated surgeries were required in 30% to 50% of patients.11,14–16 There are many possible reasons that additional surgical procedures are frequently needed in patients with infantile esotropia. According to our experience, these reasons may include inaccurate measurement of the angle of deviation due to the patients being infants, miscalculation of oblique and vertical muscle functions, the presence of an unrecognized accommodative component, and performing surgery before angle stabilization. Moreover, performing surgery in the smaller eye and orbit of children may lead to the surgical technique being more challenging.

The incidence of amblyopia in patients with infantile esotropia is variable in the literature. Louwagie et al17 reported that the frequency of amblyopia ranged from 29.4% to 55.8%. In an important study by Ing,18 the results of 106 patients who underwent surgery for infantile esotropia showed that after an average follow-up of 8.4 years, amblyopia defined as a BCVA difference of one line or more was detected in 41% of patients. According to the results of our study, amblyopia at several levels was detected in 46.8% of the patients. No relationship between surgical timing and amblyopia was detected.

The pathogenesis of the disease is still not fully understood, but two conflicting theories have been postulated.6 The Worth theory proposes that infantile esotropia results from a congenital deficit in the fusion center of infants and these patients can never achieve good binocular vision despite complete correction.6 In contrast to the Worth theory, the Chavasse theory proposes that the main problem is a delay in motor development and ocular alignment achieved during infancy could potentially result in good binocular vision.6

The ELISSS study showed that only 3.9% of patients in the late group (32 to 60 months) versus 13.5% of patients in the early group (6 to 24 months) recognized the fly on the Titmus Fly test.13 Ing18 also investigated the development of stereopsis and motor fusion according to surgical timing, finding that there was no difference in patients who underwent surgery before the age of 24 months, but patients who underwent surgery after the age of 24 months had a significantly lower percentage in depth perception.

Helveston et al8 reported 10-year follow-up results of 10 patients with infantile esotropia who underwent surgery at 16 to 23 weeks of age and the results showed that stereopsis was detected in four patients.

Stereopsis levels were 3,000 seconds of arc in 2 patients, 400 seconds of arc in 1 patient, and 140 seconds of arc in 1 patient. During the 10-year follow-up, at least 1 additional surgical procedure was required to maintain ocular alignment. The authors indicated that, high-grade stereoacuity was not solely dependent on surgical timing and was difficult to attain, even with early successful alignment.

Parks et al6 presented the results of 79 patients who underwent surgery for infantile esotropia. Stereopsis between 100 and 3,000 seconds per arc was detected in only 39% of patients. The authors compared the results with patients with accommodative esotropia to garner a better understanding of why patients with infantile esotropia could not have high-degree stereoacuity. In patients with accommodative esotropia who underwent surgery at the same age and with the same surgical success, stereopsis was detected in 98% of patients. Parks et al8 argued that the low degree of stereoacuity in patients with infantile esotropia might also be due to the genetic feature of disease, and not only surgical timing. Birch et al19 reported the results of 73 patients with infantile esotropia in whom surgical success (defined as final angle of deviation smaller than 8 PD) was achieved in 80% of patients. In 41.1% of patients who underwent surgery before the age of 16 months, the random dot stereopsis test was positive; however, no effect of surgical timing on stereopsis was detected. In addition, 60 seconds of arc stereopsis was detected in only 2 of 73 patients.

In another important study by Birch et al,20 the importance of the duration of misalignment rather than early surgical timing was emphasized. The study enrolled 129 patients with infantile esotropia who had similar onset of esotropia. After a minimum 5-year follow-up, a total of 36.4% patients demonstrated some stereopsis, 21.7% passed the random dot test at 500 seconds or better. The prevalence of random dot stereopsis was 65% in patients whose alignment was achieved within 3 months from the onset of esotropia, whereas it decreased to 4% when alignment was delayed at least 1 year from onset. The authors emphasized that early surgical correction was associated with better stereopsis because it minimized the duration of misalignment, rather than the importance of the critical period of visual maturation. In our study, at the end of the 8-year follow-up, stereoacuity was detected in 15.2% of 79 patients who underwent surgery between the ages of 6 and 27 months; 83.3% had only gross stereopsis (3,000 seconds of arc). The mean age at the time of surgery of patients in whom stereopsis was detected was 10.4 ± 3.5 months.

Stereoacuity may develop in patients with infantile esotropia when orthotropia is provided by successful surgery. However, it is clear that early surgical alignment is not sufficient for the development of high-grade stereopsis. Due to the nature of the disease, the maturation of stereopsis may not be affected by only surgical timing. How the patients were followed up after surgery and how the refractive errors were corrected is important. Additionally, the degree of amblyopia and the therapy (including the amount and length) may also have a great impact on the development of stereopsis. Still, it appears to be the only valued treatment option for the development of stereopsis. Moreover, stereopsis may be the best prognostic postoperative finding, and it is important in helping a child maintain alignment. Nevertheless, early timing of surgery results in an increased need for repeat surgeries. Patients should be examined several times before surgery to be sure of the correct measurement of the angle of deviation without delaying the operation. The family should also be informed about the possibility of multiple operations.

Due to the retrospective nature, the current study had some deficiencies. These patients do not always present to an ophthalmologist at 3 months old, which may be the best age for surgery. Many patients present at an older age. Therefore, the current study may also help ophthalmologists answer patient questions and explain what to expect in the future. This inference cannot be made directly from the results of this study, but according to our experience, treatment is not completed surgical procedures only. Patients should be followed up regularly, and amblyopia treatments and refraction corrections should be applied when necessary.

References

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  8. Helveston EM, Neely DF, Stidham DB, Wallace DK, Plager DA, Sprunger DT. Results of early alignment of congenital esotropia. Ophthalmology. 1999;106(9):1716–1726. doi:10.1016/S0161-6420(99)90337-8 [CrossRef]
  9. Çerman E, Eraslan M, Ögüt MS. The relationship of age when motor alignment is achieved and the subsequent development of stereopsis in infantile esotropia. J AAPOS. 2014;18(3):222–225. doi:10.1016/j.jaapos.2013.12.017 [CrossRef]
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  11. Louwagie CR, Diehl NN, Greenberg AE, Mohney BG. Long-term follow-up of congenital esotropia in a population-based cohort. J AAPOS. 2009;13(1):8–12. doi:10.1016/j.jaapos.2008.06.013 [CrossRef]
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  13. Simonsz HJ, Kolling GH, Unnebrink K. Final report of the early vs. late infantile strabismus surgery study (ELISSS), a controlled, prospective, multicenter study. Strabismus. 2005;13(4):169–199. doi:10.1080/09273970500416594 [CrossRef]
  14. Birch E, Stager D, Wright K, Beck RPediatric Eye Disease Investigator Group. The natural history of infantile esotropia during the first six months of life. J AAPOS. 1998;2(6):325–328. doi:10.1016/S1091-8531(98)90026-X [CrossRef]
  15. Gursoy H, Basmak H, Sahin A, Yildirim N, Aydin Y, Colak E. Long-term follow-up of bilateral botulinum toxin injections versus bilateral recessions of the medial rectus muscles for treatment of infantile esotropia. J AAPOS. 2012;16(3):269–273. doi:10.1016/j.jaapos.2012.01.010 [CrossRef]
  16. Ing MR, Norcia A, Stager D Sr, et al. A prospective study of alternating occlusion before surgical alignment for infantile esotropia: one-year postoperative motor results. J AAPOS. 2006;10(1):49–53. doi:10.1016/j.jaapos.2005.09.006 [CrossRef]
  17. Louwagie CR, Diehl NN, Greenberg AE, Mohney BG. Is the incidence of infantile esotropia declining?: A population-based study from Olmsted County, Minnesota, 1965 to 1994. Arch Ophthalmol. 2009;127(2):200–203. doi:10.1001/archophthalmol.2008.568 [CrossRef]
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  19. Birch EE, Stager DR, Everett ME. Random dot stereoacuity following surgical correction of infantile esotropia. J Pediatr Ophthalmol Strabismus. 1995;32(4):231–235.
  20. Birch EE, Fawcett S, Stager DR. Why does early surgical alignment improve stereoacuity outcomes in infantile esotropia?J AAPOS. 2000;4(1):10–14. doi:10.1016/S1091-8531(00)90005-3 [CrossRef]

Patient Demographic Dataa

VariableEarly Group (n = 27)Late Group (n = 26)Very Late Group (n = 26)Total (N = 79)PStatistical Analysis
Age at the first examination (months)7.6 ± 1.8 (3 to 11)12.2 ± 3.4 (3 to 17)15.0 ± 6.0 (4 to 26)11.5 ± 5.1 (3 to 26)< .001One-way ANOVA
Follow-up duration (months)95.5 ± 39.4 (50 to 180)95.9 ± 47.4 (39 to 240)98.6 ± 33.6 (27 to 144)96.6 ± 40.0 (27 to 240).779One-way ANOVA
Preoperative angle of horizontal deviation (PD)54.1 ± 17.8(30 to 90)48.9 ± 12.1 (30 to 80)49.6 ± 11.0 (30 to 70)50.9 ± 14.0 (30 to 90).659One-way ANOVA
Refractive errorb (D)1.93 ± 0.90 (0.50 to 3.50)1.58 ± 1.24 (−2.00 to 3.50)1.80 ± 0.98 (0.00 to 3.50)1.77 ± 1.04 (−2.00 to 3.50).4765One-way ANOVA

Distribution of Follow-up Durations According to the Groups

VariableFollow-up Duration 24 to 60 MonthsFollow-up Duration 61 to 120 MonthsFollow-up Duration > 120 Months
Early group (n = 27)8 (29.6%)11 (40.7%)8 (29.6%)
Late group (n = 26)6 (23.1%)14 (53.8%)6 (23.1%)
Very late group (n = 26)5 (19.2%)15 (57.7%)6 (23.1%)
Total (N = 79)19 (24.1%)40 (50.6%)20 (25.3%)

Coexisting Clinical Findings of Patients

VariableEarly Group (n = 27)Late Group (n = 26)Very Late Group (n = 26)Total (N = 79)PStatistical Analysis
Nystagmusa1 (3.7%)2 (7.7%)3 (11.5%)6 (7.6%).518Fisher's exact test
Patern deviation2 (7.4%)1 (3.8%)1 (3.8%)4 (5.1%)1.0Fisher's exact test
IOOA9 (33.3%)11 (42.3%)15 (57.7%)35 (44.3%).197Pearson chi-square
Cross fixation8 (29.6%)15 (57.7%)4 (15.4%)27 (34.2%).005Pearson chi-square
DVD2 (7.4%)0 (0.0%)5 (19.2%)7 (8.9%).045Fisher's exact test
AHP0 (0.0%)0 (0.0%)1 (3.8%)1 (1.3%).658Fisher's exact test
Vertical deviation0 (0.0%)2 (7.7%)4 (15.4%)6 (7.6%).078Fisher's exact test

Comparison of Final Motor and Sensory Outcomes of Patients

VariableEarly Group (n = 27)Late Group (n = 26)Very Late Group (n = 26)Total (N = 79)PStatistical Analysis
The final angle of horizontal deviation (PD)a14.0 ± 10.6 (0 to 40)11.4 ± 8.7 (0 to 30)10.7 ± 9.0 (0 to 35)12.1 ± 9.5 (0 to 40).403One-way ANOVA
Surgical success7 (25.9%)6 (23.1%)14 (53.8%)27 (34.2%).035Pearson chi-square
Second surgery12 (44.4%)15 (57.7%)8 (30.8%)35 (44.3%).148Pearson chi-square
Third surgery7b (25.9%)1 (3.8%)1 (3.8%)9 (11.4%).014Pearson chi-square
Operations per child1.74 ± 0.94 (1 to 4)1.62 ± 0.57 (1 to 3)1.35 ± 0.56 (1 to 3)1.57 ± 0.73 (1 to 4).020Pearson chi-square
Amblyopia13 (48.1%)13 (50.0%)11 (42.3%)37 (46.8%).845Pearson chi-square
Stereopsis10 (37.0%)1 (3.8%)1 (3.8%)12 (15.2%).001Fisher's exact test

The Comparison of Results at the End of 24 Months of Follow-up and at the Final Visit

VariableResults at the End of 24 Months of Follow-upResults at the Final Visit


Surgical SuccessSecond SurgerySurgical SuccessSecond Surgery
Early group (n = 27)9 (33.3%)9 (33.3%)7 (25.9%)12 (44.4%)
Late group (n = 26)6 (23.1%)3 (11.5%)6 (23.1%)15 (57.7%)
Very late group (n = 26)14 (53.8%)1 (3.8%)14 (53.8%)8 (30.8%)
Total (N = 79)29 (36.7%)13 (16.5%)27 (34.2%)35 (44.3%)
Authors

From the Department of Ophthalmology, Eskisehir Yunus Emre State Hospital, Eskisehir, Turkey (OEM); and Department of Ophthalmology, School of Medicine, University of Hacettepe, Ankara, Turkey (ASS).

The authors have no financial or proprietary interest in the materials presented herein.

Correspondence: Omer Ersin Muz, MD, MRCESd (Ophth), Department of Ophthalmology, Eskisehir Yunus Emre State Hospital, Uluonder Mah., 26190, Tepebasi, Eskisehir, Turkey. Email: ersinmuz@gmail.com

Received: December 25, 2019
Accepted: April 24, 2020

10.3928/01913913-20200708-01

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